Ask Ian: What is Headspace? (And Why It Matters)

[@BigBadBalrog]

It always surprises me when Ian explains the topic in the first 30 seconds, but then continues to give us a stream of useful info for the next 10 minutes plus

[@bpomowe224]

I'm no longer surprised, only delighted.

[@stitch626aloha]

Ian’s video is how they USED to teach how to write a research paper. Tell the Reader what you’re going to explain. Explain what you said you would explain. Sum it all up.

[@ForgottenWeapons]

Lol - even now so many years later the five paragraph essay format is burned into my brain from high school.

[@alexbellington9243]

@@ForgottenWeapons introduction, body, conclusion

[@01Bouwhuis]

Mc collum...he could be irish....chieftain does te same

[@marknovak8255]

The thickness of a sheet of paper is the difference between too short and too long. Well said sir.

[@LKaramazov]

Yeah, that’s the crazy part to me as a newer shooter. I hear people talking about putting a piece of scotch tape on the bolt, I guess, and I’m like, “ really?”

[@mikehipperson]

That's what she said!

[@marknovak8255]

@@karlhillenbrand8447 Note, im not here to steal his thunder, merely add to it. His explanation is quite good.

[@josuelservin]

@@marknovak8255 I appreciate the input from an expert, so thanks for chime in!

[@theq4602]

roller bearings are the same way except they need tolerances down to 0.0001 or sometimes less

[@waylonsmythers7714]

Overlaying a physical bullet onto a diagram ,while explaining different processes & issues, really helps to understand them better. Please do some more like this in the future.

[@hcnif55]

Just wished he had some blue tac or a little bit of tape to stop the bullet rolling off. (to be used on the paper to make a chuck, not sure putting anything sticky on a bullet will do any good)

[@robinblackmoor8732]

If Firearms 101 was a college class, Ian would be the professor that everybody on campus wants to get.

[@LD-Orbs]

If colleges actually had that course - with a bit of range practice - life would be a lot better! 😄

[@micwclar]

@@LD-Orbs that sounds like a great elective class for a physics or mechanical engineering degree program.

[@gunnsmith1]

He would be the Dean

[@reliantncc1864]

It's a shame that gender studies or racial studies are preferred.

[@pierremainstone-mitchell8290]

He certainly would be!

[@Niinsa62]

I'm a technical illustrator, have been for twenty years. Your illustration of headspace is top notch. In my defense, I often have to illustrate something explained to me by someone who is not good at explaining. You obviously know what you're talking about, and you're good at explaining. Those two don't always go hand in hand.

[@onpsxmember]

Even when seen in a positive light, anyone with a year of technical drawing will miss some lines, what is/isn't cut and in which layer and what is cylindrical? It's obvious for some but not for everyone. If there were a few more bits, it'd get messy quickly. It's okay with his busy schedule and it worked, but the illustration alone is far from top notch.

[@rogerlibby14613]

@@onpsxmember I need to disagree. This is fine 9th grade drafting (not technical at all). As for the topic ... headspace is an important topic for Americans and almost no one else throughout the world.

[@johnh.tuomala4379]

There are actually three kinds of space: the space up there (“outer”), the space down here, and (the true headspace); the space between a Biden voter’s ears!

[@MrMaselko]

Videos with Ian explaining these kinds of topics are great

[@epl803]

Mark Novak over at Anvil Gunsmithing (has worked with Ian and C&Rsenal before on Project Lightening) also did a great video on headspacing if anyone wants to know more about it: kzbin.info/www/bejne/rpWqlpqQmt-dqpo

[@hhe5218]

Isn't that Headstamp?

[@cameronfelkel377]

Ian hit it on the "head" with this answer! I work at FN America in Columbia SC as a barrel QA technician in the barrel shop. This is exactly what headspace is and the importance of it being correct. If you have the experience and means to get the gages to check it , do it. If not please don't try. Excellent video on this topic Ian!

[@konstantin.v]

Maybe you can explain then why the bolt sitting flush with the barrel is actually bad? Ian's explanation about that it makes you jam the bullet too hard into the chamber doesn't seem to be relevant, because later, speaking about a gap too big, he talks about the bolt being pushed flush with the barrel anyway, by the recoil spring or by hand (5:01)

[@tz8785]

@@konstantin.v I wondered about that too, and even if usual chamber geometries require that gap, lengthening the chamber just a little and starting the rifling a little later should allow for a totally enclosed bullet. There might be less obvious issues, like increased case lengthening when firing (because the case mouth would be the only available direction for the brass to expand) or tighter required tolerances, but this is speculation on my side.

[@konstantin.v]

@@tz8785 , I'm guessing the thermal expansion: that a small gap on a cold gun is needed for when it becomes hot and the metal expands some. But it's a speculation, too 🙂

[@cameronfelkel377]

@@timewave02012 right now it just a new pistol variant and in 5.56 but you never know in the future.

[@cameronfelkel377]

@@kellyharbeson18 Ian was showing a very very simplistic way of showing why a headspace is needed and what can happen when it's not correct, now the head space is actually at the tip of the projectile when the bolt is in battery and it's the space between where the actual bullet is in contact with the chamber and the bullet lead.( The start of the lans) but if the head space is wrong it makes the bullet not seat correct and it could be to far in or , not far enough. And that's the issue Ian was drawing. And if it's in to deep the combustion can't get enough pressure and speed to push the projectile.

[@DANO-4899]

Ah, headspace and timing! Essential Marine Corps training for the Ma Duece 50 cal. Brings back fond memories .

[@slick3129]

He had one video of firing a Ma Deuce that demonstrated a trained officer checking using Go-No Go gauges. Pretty interesting.

[@tjroelsma]

The Ma Deuce 50 cal, one of the most abused and worst maintained weapons. Some of them were só worn out that it was a miracle they even managed to fire.

[@2bcoppins]

Hahaha exactly..Every time I hear head space and timing I think about the ma deuce in marine corps machine gunners course

[@robinblackmoor8732]

@@slick3129 That video is fantastic. I was never in the military, so I had no idea that was a thing.

[@aivehn]

I still have a M2HB headspace and timing guage that I picked up about the time I separated from the US Army. Ma Deuce loves both the Army and Marines, and we all love Ma Deuce right back!

[@WingZeroGWO]

I'd just like to point out that there are situations where a headspace issue is less obvious, meaning that the weapon can appear to be cycling fine for several hundred or thousands of rounds, and then suddenly detonate. Typically what happens is a minor case of the situation you were describing @4:50 but instead of the spent case producing an evident indication, what happens is the locking lugs become fatigued from repeated impact of slamming that short distance, until either the bolt lugs shear or the trunnion lugs shear.

[@hunterbidensaidslesion1356]

It might also be the case that the vast majority of carteidge-case headspacing features are produced very close to the mean dimension, with very few spread out along the entirety of the allowable tolerance. But, when you do get one that falls at or near the minimum dimension, or perhaps even below it, you are going to be having a bad day.

[@asd-km2hf]

I had a 22 rifle detonate after about 500 rounds (got it at a gun show so probably more put through it before me). Wonder if this is what happened.

[@grizzlyblackpowder1960]

Should have answered this the way my drill sergeant did for a private in my basic training: "headspace is the thing that stops your face from getting blown off, private".

[@bravo_cj]

Indeed your drill sergant is based XD

[@thegreenman2030]

I’ve known and been checking headspace on various rifle platforms for years now, that being said this was extremely informative and easy to understand for those who didn’t know or understand it.

[@spondulixtanstaafl7887]

Headspacing is one of those firearms concepts that can be tricky to understand, thanks for a thorough and concise explanation . I never tire of content like this.

[@kj3n569]

Class is in session. Professor Gun Jesus teaches more about head space in 10 minutes using hand drawn diagrams with an actual cartridge overlay than probably 90+% of us knew from years of being pew-thusiasts. Yet another reason to live this channel. Thanks Ian. Merry Christmas! May all of your head spaces be just right, your Scotch be a fine single malt and your shots be inside the 10 ring.

[@andrew69novak]

Thanks! Always enjoy your videos. I particularly appreciated this one.

[@SamGray]

I had an SMLE with blown out headspace, so, of course, it was non-firing and used as a wall hanger. A certain thief stole it, along with other items, and the police were unable to find said thief. I often wondered if they ever tried to fire it.

[@joshweed123]

He probably got to fire it once 😅

[@hurricane567]

American police recover stolen guns with the same cartridges that were in them when they were stolen.

[@drrocketman7794]

​@@joshweed123Darwin award

[@renatapakuwalker8190]

ok fair enough i owe you a SMLE and some other items but dude you owe me 2 hands and a right eye

[@boingkster]

It's really important if you want to have a properly functioning, safe and accurate firearm. If you have too loose a tolerance you will find that the brass backs out of the chamber under pressure and ruptures at the case head (bottom of the brass) which vents hot gas at the shooter, or has too large a gap to jump the projectile to the rifling which causes accuracy issues, among others. I've experienced both but never severely. I've also seen a few Lee Enfield conversions which had such severe headspace issues they ruptured every case they fired just above the case head. I immediately told that shooter the short explanation and that he really should take it to a gunsmith to fix. I never saw him again but I hope he listened. Awesome work on the video, Ian, and a really good illustration on what the problem is and how to identify it! As always, keep up the good stuff.

[@Peter-ur3yy]

These videos are arguably my favourite. Helps you to understand a lot more of what the weapon rundown videos are actually talking about.

[@iainbaker6916]

It’s easy to forget until you see a video like this just how ingenious a design a modern firearm is. Probably why the design hasn’t really changed much in the last 100 plus years - it’s hard to improve on such a fundamentally sound design.

[@dalevines8832]

I used to run the calibration lab on the USS Carl Vinson. We calibrated everything. From headspace gauges to rubidium oscillators. Oscilloscopes, spectrum analyzers. It was good.

[@chemistryofquestionablequa6252]

That sounds really cool and interesting.

[@stephenhood2948]

rubidium oscillators?? Did you just make that up?? LOL That particular job sounds fascinating, care to elaborate a bit?? Id love to hear some stories!!

[@stephenhood2948]

I see that is a real thing, some kind of atomic clock. Wasn't trying to rag on your comment, that just sounds kind of made up.

[@TheFlutecart]

I still have dreams about carrier duty. Likely the most dangerous and focused part of my life. There's nothing quite like it. I was IC PLAT/Lens shop, V2 Division. Pilot landing optics (the ball) and deck cameras. USS Lexington AVT-16, 89-91.

[@petervienna1550]

Very very good video! When I bought my (brand new) AK here in Austria a few months ago - having no previous practical experience with guns - the guys in the gun shop DID NOT KNOW THE TERM HEADSPACE ! When I told them that I heard a lot about headspacing on videos of Brandon Herrera and other people, they said something like Headspacing would surely only be some problem of the americans and that they don't have that kind of issues with their guns in the shop... Later I found out that they primarily sell AR-style Rifles and only the expensive kind, they don't really build guns themselves (only minor repairs and stuff like that). So they might never have had issues with improper headspacing (of course they only use best-of-the-best ammo, too). But still, this should have been a major NO-GO for me. Now I know better and with Ians excellent explanation, I know why it is really important.

[@ryllharu]

I bought Go/No-Go gauges for checking headspace on some surplus stuff. Check them every time. I've found a few that weren't cleanly passing at a major retail chain. I did notify the staff.

[@hoosierplowboy5299]

Excellent explanation and advice. I had a.222 that I handloaded for about 35 years ago. Inherited from my Dad, who bought it from a neighbor. All went well, until I had a case separation due to excessice headspace. Luckily, I was wearing shooting glasses and escaped injury when the case ruptured...

[@dylan-fr3bh]

Ian, i know you've made lots of these q&a videos, but I just have to say I love the format

[@martinswiney2192]

Would love to see more videos like this. I like the old obscure gun videos you primarily put out but this is some useful information that can save someone from injury or worse. Great content as always.

[@drboris01]

I was waiting for you to mention the Turkish SMLE conversion. Thanks for making it so simple for us not very technical firearm lovers out there.

[@redheadmetalhead247]

Excellent explanation of headspace and why it matters. I really enjoy building as much as I do collecting, and I frequently get asked for tips on building (especially AKs), and I'm always having to give a lecture on how important headspacing is. Now I can just link this video!

[@markjordan348]

This was a very good basic explanation of headspace and its role in safely firing the firearm. I would like to see follow-up videos on ways of achieving headspace. Rimmed cartridges versus belted cartridges versus semi-rimmed versus shouldered versus head spacing on the case mouth. All but semi-rimmed have their advantages. Secondly I would like to see the effect of headspace on accuracy particularly in the case of 38 Super where it is a semi-rimmed cartridge but gets increased accuracy when the firearm is set up for to headspace on the case mouth. And finally it would be nice to see a comparison of say a military chamber versus a match or even bench rest chamber. There used to be guys that would shoot an entire benchrest match with one casing! Punching out the primer between shots priming it with a hand primer measuring the powder charge and seating the Bullet by hand. And yes when it comes to stating something in the first 30 seconds and then rambling on for a stream of Consciousness for 10 minutes I'll try and give Ian a run for his money!

[@stephenhood2948]

That is very cool!! I didnt even know someone could do such a thing at the range.

[@markjordan348]

@@stephenhood2948 I don't know if they still do it. But these guys would cut their Chambers so tight that the cartridge would just chamber. And the neck of the chamber was cut to only let the brass expand enough to release bullet. So after they fired the shot the neck would shrink back down enough to hold the bullet. When they seated the bullet it was long enough to touch the rifling when chambered. They did all this to eliminate the variable case volume from one to the other and to make sure the bullet started from exactly the same place in the bore every time. But remember they were shooting groups measured in inches at a thousand yards and this was 30 possibly 40 years ago. Ammunition quality control has improved quite a bit.

[@bulukacarlos4751]

Excellent video!, and I'm glad that another engineer, 10,000 km from my house has the same hand-CAD skills as me. Greetings from Argentine Patagonia.

[@darrellh1840]

Great explanation and illustrations Ian! Thank you! I have always purchased headspace gauges for military surplus rifles…

[@jameskilpatrick7790]

Well explained, as always. I'm currently putting together an AR15 from parts, (WWSD homebrew), and took delivery of a .556 headspace "No Go" gauge yesterday, along with the action tool I plan to use when mounting the barrel. It's just common sense, once you understand the issue.

[@6Sally5]

Just in the first thirty seconds you explained this so much clearer than any other I have seen! So many seem to make this so difficult to understand…especially to new firearms owners and new reloaders!

[@calikid3336]

Great video; nice tip on head-spacing when building a firearm from parts; I built semi, closed bolt Mk-2 and Mk-3 Stens and they work great. However, I want to mention that while building & testing: I had one 'blowback' experience when I put in too light of a recoil spring in accidently; Very glad I was wearing eye protection as the blast pressure found every place where my shooting glasses leaked, woke me up. The semi-Sten has 2-springs instead of one and the spring travel-length sort of leaves it almost loose when closed & loaded, then has an over-tight 'accelerated spring compression when cocked back past the sear locking point to the bolt-stop. I might try an Uzi recoil spring. The surplus WW-2 mags worked great, most were stored well and 70% weren't worn out. The closed-bolt semi-Sten doesn't jam and feeds hollow points and flat-noses easily when Uzi only takes FMJ ammo.

[@_ArsNova]

Excellent video, and definitely one of your most informative "intro to firearms terminology" sorts of videos. I hope novices 20 years from now will still be learning from this. Keep it up Ian!

[@qinarizonaful]

Super explanation, Ian! And one can clearly see how Hybrid (Stainless Steel) base on the cartridge case allows higher pressures and no blowout until the pressure is dropping as the bullet travels down the barrel, and then unlocks the bolt, still at higher pressure, and the case base is strong enough during extraction with higher camber pressure! Good place to show this on your super diagram!! ❤

[@felisconcolor1112]

This explains the "why" of belted magnum cartridges: that massive back end is not to prevent blowouts, but to ensure the headspacing is perfect for those high pressure rounds.

[@SlavicCelery]

It's akin to headspacing off of the rim. Although, you gain better feeding characteristics with a belted cartridge vs rimmed.

[@ScottKenny1978]

Yup. It's about having nice feeding characteristics like a rimless case, but the very positive headspacing of a rimmed cartridge.

[@justnotg00d]

I actually remember this. In training, with good ole Ma-Deuce, we had a go-no-go gauge to check the head space and timing. Of course when some "other" soldier was missing the target (not me, I always hit what I aimed at) the soldier would say that the head space was off. The drill sergeant replied, "Yeah, I think you're right, the Operator head space and timing is off !"

[@LeeMorgan07]

I like how this video bleeds into how to look at older guns that were re-chambered, etc.

[@rhekman]

I thought about a set of go/no-go guages when building my first AR. Fortunately on that platform, upper receivers aren't really critical to achieving proper headspace. I just bought a bolt carrier group and a barrel from the same manufacturer, and said YOLO. Brass looks great and it's the most accurate gun I own.

[@g24thinf]

I headspace all my AR builds, better safe than sorry

[@tonycs-9]

Headspace on a AR is at the bolt face and barrel extension/ barrel assembly. You can buy a bolt not cut right or a barrel that has not been cut right or extension not cut right or installed wrong. Buy headspace gauges.

[@johns2631]

Generally speaking if an AR platform will not forward assist to chamber while of course on Safety there is a problem. When done don't forget to clear the chamber.

[@RAkers-tu1ey]

Great explanation. A really crucial piece of information for weapons which get frequent barrel changes - M2, Mg-42, etc.

[@Nimbleshooter]

As someone interested in the engineering on firearms I always wondered what headspacing was. Thank you Ian!

[@aries_9130]

This is one of the best explanations of headspace I have ever seen.

[@georgedoolittle7574]

*"head space and timing"* to be precise but absolutely spot on here.

[@CatFish107]

Thanks for the quick bit of info at the end to give me a rough idea how headspace is set initially. Neat trivia. My milsurp was new old stock pla sks. Wonderful.

[@lubossoltes321]

It's always a pleasure when somebody asks the right question and give Ian the opportunity to create such an informative video answer. Thank you for asking !!!

[@ericmcguire9573]

My roommate had a sporterized 1917 Enfield. We took it out back to try out a couple of old guns. I loaded it up with Ferderal .30-06 and fired it. It felt like I had been hit in the cheek with a hammer. The case had burst from the head to about an inch up the case wall. Gas shot down the bolt track, blew out the bolt release, singeing the skin on my thumb and blasting gas and unburnt powder into my face. I touched my face to find blood. The powder had been lodged in my skin leaving a perfect outline of my safety glasses. I spent the next week picking grains of powder out of my face.

[@AndiRose21]

An absolutely excellent explanation of the question in a comprehensible manner. Not only is the content interesting, it is easy to understand. Thank you.

[@oscarfloyd2678]

Another Rifle that is notorious for headspace, is the No.5 Rolling Blocks in 7mm Mauser. Due to the change in the case dimensions in 1910s, modern 7mm mauser usually doesn't headspace correctly in the old Rolling blocks

[@anthonyburke5656]

This took me back to my early soldiering and being taught the Browning 30 cal MG. Of course, the lessons there generalised to the M2 later. I formed the “habit” of carrying my own specialised tools, for things like measuring headspace and extracting separated cases. In SVN it was surprising how often and for what purposes my little toolkit came into use, not only for my unit, but other things. I recall getting a chainsaw operative using the kit and fixing range finding radar using parts of the radar toolkit and my own tools.

[@Sightbain.]

Really well detailed and interesting this style of QA is definitely a success, that isn't to say that I don't miss the hour long ones as well.

[@lufiron]

As someone getting into just getting into gunsmithing for 3 gun competitions, this was timely and highly informative, thank you.

[@stephenhood2948]

How do you get started in such a thing?? Did you take some gunsmithing classes?? Are there even gunsmithing classes?? I would think there would be, but have never heard of any and would like to do such a thing myself. I'm pretty competent, maybe knowledgeable as to function would be a better phrase, but very far from calling my self a gunsmith. The different actions utilized by so many guns is fascinating. The amount of precise timing that must take place for a gun to cycle properly and safely is very cool. Reloading is another thing Id like to give a shot as well.

[@lufiron]

@@stephenhood2948 Well, I am an auto mechanic in real life, and the concepts of exerting pressure against an object in a cylinder using an explosion isn't a foreign one to me. To answer you question though, theres the Sonoran Desert Institute if you want professional instruction.

[@stephenhood2948]

@lufiron Yeah, I wrench for a living as well. Tired of smashed, dirty knuckles, and guns have always fascinated me. Not long after posting that comment I saw an online gunsmithing class advertised on Military Arms Channel, cant remember the name. I requested an info pack from them. Good luck!! We should all find what makes us happy and pursue that.

[@wishuhadmyname]

Regarding the ability of brass to expand, I found that out *almost the hard way last week. Somehow, a 5.56x45 cartridge wound up as the first round in my 7.62x39 AK magazine. I loaded it into my AK, pulled the charging handle back, released it, and noticed the bolt did not go all the way into batter. I pulled it back again to visually confirm nothing was in the way, and tapped it forward to manually close it. I pulled the trigger and there was a small puff out the muzzle and the bolt didnt cycle. I removed the magazine, locked the bolt back (thank you Zastava for a safety lever that do that), and the case didnt come out. It took very little effort to pry it out with a pocket knife and the front 1/3 of the 5.56 shell from the shoulder back had swollen to fill the 7.62mm chamber. If it had been poorly made ammo or steel cased, I likely would have had a catastrophic failue

[@Tomcattube1]

Wow, thank you for explaining this so clearly. When in the military I had to conduct headspace checking on my automatic weapon. But to be honest I really didn’t know what or why I was doing it. Now I do! Of course I have not had to do so in many decades, but hey, cool to finally understand why they had us doing it!!

[@GunsmithSid]

Ian has come a long way since he started. Good presentation. 😊

[@WarmPudgy]

Ian, thank you for your wonderful illustrations!

[@cw5865]

The best explanation I have seen yet. ESPECIALLY with your diagrams, great job...

[@jeffreyhooper3678]

I remember reading somewhere that headspacing problems can be often seen in model 1895 Winchesters chambered in 30-06 because over time that incredibly powerful cartridge can actually compress the bolt's steel. The author of the article highly recommended that headspacing be measured before the gun is shot and before the gun is bought.

[@Bacteriophagebs]

Not a headspace issue, but similar: One time when I was at the range, one of the range officers came over to me and asked if another guy could use one of my cleaning products. He'd seen I had a kind of "blast-free" cleaner and another guy at the range had managed to get loose powder inside his gun. I went over to see and found that the guy was using reloads in his .223 bolt-action and was using 60+ grain bullets in what was designed to be a varmint rifle. He'd set the bullets too far forward in the brass or the rifle wasn't built for that heavy/long a bullet (varmint loads are usually under 45 grains), so when he chambered a round, the bullet was rammed into the rifling. If he fired the round, it was no big deal, but when he tried to clear the chamber at the end of a relay, the bullet had remained stuck in the rifling as the brass was extracted, letting the powder pour out of the case. More importantly, the bullet was still in the barrel, something neither the shooter nor the range officer had realized. If he'd chambered another round and forced the action closed hard enough, it would have shoved the bullet of the new round back into the case, pushed the old bullet deeper, or both. This can also happen with too little headspace.

[@rileyknapp5318]

Thank you for this video! I watched your video on the Browning M2 and got a lot of question marks over my head when you started talking about adjusting the head space.

[@marioacevedo5077]

Great video. A gunsmith told me that stovepiping with Star B and Super Bs is caused by head space problems caused by wear.

[@TheGearhead222]

Great video , as always. Am a bit surprised that headspace tolerance between rimmed, semi-rimmed and rimless cartridges was not really explained. Rimmed cartridges are MUCH more forgiving of headspace tolerances, as the rim is actually part of the headspace. I own an SMLE in .303 British rimmed and discovered while rebuilding it that the gun safely fires with the original, very worn bolt head and the replacement ,newer bolt head. The replacement bolt head locks up much tighter than the original, but there is no case deformation nor gas leakage using either bolt head. As an aside, I rebuilt a CETME clone by replacing the worn bolt head and rollers with a new bolt head and +.04mm rollers. Although it uses a rimless NATO round (and was borderline out of headspace tolerances), the CETME clone safely fired with no case deformation using both the original , out of spec bolt head/rollers and the replacement bolt head and rollers. My dollars worth-John in Texas

[@alancranford3398]

Thank you for a very concise explanation of headspace. Most semiautomatic firearms have "timing" that has been set by design--the disconnector won't let the gun fire when the bolt is out of battery. That would be another subject you might explain in a future video. The M16 was designed to run at around 600 rounds per minute in automatic fire mode but switching from cannister powder to ball powder upped the rate to nearly 1000 rounds per minute. This excessive fire rate caused malfunctions until the buffer assembly was beefed up to drop the cyclic rate and some other modifications were made. Older machine guns such as the Maxim needed to be tuned by setting the timing after setting the headspace on a new barrel because 19th Century manufacturing tolerances and anticipated service life of decades and millions of rounds fired were only supportable by making headspace and timing on machine guns adjustable. When the disconnector becomes worn, the gun can fire out of battery--slightly out of battery can be misdiagnosed as a headspace problem when the timing is off due to wear or improper adjustment. Revolvers are prone to timing issues, manifested in the cartridge firing when cylinder and barrel are not fully aligned. That's the adventure of antique firearms--solutions to manufacturing tolerances bring on new problems.

[@peghead]

The M1 rifle utilizes a bolt design that prevents the hammer from striking the firing pin unless the bolt is in battery, but, that feature is useless in the case of an out-of-battery 'slam-fire'. It is important, especially for hand loaders, that the primer pocket is uniformly reamed so that the primer sits .006" below flush. Military primers are slightly thicker than commercial offerings. The free-floating M1 firing pin will leave an 'indent' on the primer of a chambered round and a primer sitting too high can detonate.

[@willardjohnson3832]

Excellent explanation. Now I understand headspace a lot better.

[@mikeseigel6566]

Ian, this is exactly how headspace was explained to us at GM A School in the Coast Guard many years ago. Super easy to understand.

[@RichardHopkinsLobosSolos]

A friend of mine, another Ian as a matter of fact, has been known to say that someone needs to adjust their headspace and timing. This helps me to understand part of that.

[@keithdurose7057]

The BREN cleaning kit in the spare parts wallet. Had a ruptured case extractor in it. I never experienced a ruptured case,but it was invaluable and also worked on the LMG and FN L1A1 SLR. In British service.

[@douglasmcneil8413]

Thank you for clearing that up for me. I had a good general idea about what headspace was. But it's nice to have something like that explained properly for me.

[@QuintusAntonious]

Man perfect timing on this video, Ian! I'm about to purchase a surplus Garand from CMP, and this was super helpful!

[@peghead]

I'm pretty sure the CMP wouldn't let a Garand out the door without it passing a headspace check, enjoy your M1.

[@jamescherney5874]

Thought I knew what headspace was but more to it than realized. Ian is an outstanding teacher!

[@bwhog]

It's also worth commenting that even with safety measures, an over pressure cartridge can still blow the top off the barrel. An especial concern for hand loaders. After inspection, with any new acquisition that isn't fairly new (like less than 20 years), after thoroughly inspecting the rifle at home and determining it is something I'm comfortable taking to the range, my habit is to fire the first round at waist level and as far off my body as I can get it. Then I very carefully inspect that first case before I fire it again. When I'm confident it isn't going to blow up on me, I'll sit down at the bench but I'll still inspect the next four or five cases and look for changes. I have never had a failure yet (* knock on wood * ) but I have seen a few things that were concerning, mostly about the primer. With those calibers for which I have a number of examples, I obtain gauges to make certain, such as with the Mosin-Nagant collection since those often have substantial wear. because at that point, it's a justifiable expense.

[@terrycostakis6284]

One of the best explanations of headspace for the novice that I've seen. It's a commonly misunderstood topic because most explanations are too technical

[@rogergadley9965]

An example of a headspace problem happened to me. I bought one of the surplus Italian Army Carcano 6.5 mm rifles about the same time Lee Harvey Oswald bought his. The things were dirt cheap. I think mine was $16 or $17. I also got some surplus ammo. I noticed that the bolt rattled a bit. It tightened up a little with a round in the chamber, but was still sort of loose. The first time I shot it a spray of debris hit me in the forehead, above my right eye. I put on a pair of sunglasses (as an ad-hoc substitute for shooters safety glasses) and fired again (I know, a stupid thing to do, but I was 15). Same thing happened, a spray of dirt and unburned Italian smokeless powder hit me in the forehead. The next thing I did was a little smarter; I never shot the rifle again.

[@randmayfield5695]

I wanted to buy the CZ-457 rifle with the three barrel set (17HMR, 22LR, and 22WMR) but it was unavailable so I bought the rifle in 22LR and barrels for the other two calibers separately. Being new to shooting I had no idea about head space until I read the warning about checking it from CZ. So I did my homework and educated myself on what it was, how to check it, and then do the fix if needed. I went local at first and every gunsmith I asked told me to "Just shoot it and see." So that didn't sound right and I bought the 'go', 'no-go' gauges which in itself turned out to be a wild goose chase as they weren't immediately available. I eventually waited for a run to be made on the 22 rimfire gages and got the job done. In the end it just made me a better shooter. Also, I wouldn't let a gunsmith in my city change the batteries in my flashlight let alone do anything to my guns. "Just shoot it...." lol.

[@alexanderjones2126]

Thank you for the info, Like many of your other 'info' type vids, you are clear and explain what you are talking about well enough for even a novice to understand. I don't actually own any kind of firearm, but I wish to in the future, and 'Headspace' was a term I didn't really understand because no one outright explained it. I've heard it mentioned several times, in particular with regards to an issue that the Browning M2 had, but I didn't really know what that meant, other than the context it was used telling me that it had something to do with how the cartridge fits in the chamber. You have cleared up the issue nicely, and now I can see why the M2 having an issue with headspace could be really bad. .50 BMG with too much headspace sounds like a 'Significant Emotional Event' waiting to happen.

[@PianoMan347]

Also advisable to have headspace checked if your AR barrel and AR bolt were purchased separately. My local gunsmith charged me $2 and it took 60 seconds. AND if you use the thing defensively, a receipt for a headspace check can demonstrate that you are safe & responsible.

[@TheGruntski]

The venerable old .50 cal has a screw in replacement barrel. So there was a headspace tool which you used to set the head spacing correctly. It also resulted in many comments about people needing to check their head spacing.

[@pigpen5145]

Excellent video, explaining what is to many of us sort of assumed by the old guys in the shooting world. I had a sort of working knowledge, but not a total understanding like I do now. Many thanks.

[@jeskormanak1029]

In the 80's setting up a M-1919 Browning was easy if you didn't have the gauges handy-in Canada we used a nickle and dime. Convenient for all of us in a hurry. Go and no-go so you knew for sure. Resetting the headspace was a bother but considering what could happen made it worthwhile.

[@R3dp055um]

Good video! I am accustomed to thinking about & dealing with headspace from a reloader's POV, which is a different aspect of the same issue; it's the cartridge you're worried about, not the firearm itself. I would also respectfully point out that "headspace" is also a verb, meaning how the depth of the cartridge in the chamber is determined. In the example of the bottleneck rifle cartridge you're using, it headspaces on the shoulder. With straight wall rimmed cartridges like 357 or 44 magnum, obviously it headspaces on the rim. I have read that some of the very old belted cartridges headspaced on the belt. But apparently the belt on the 7mm Rem Mag is purely decorative. Anyhow, complex subject. One could go on for hours.

[@traceybest8047]

Excellent discussion. Also, your voice is pleasant on the ears, your precise way of speaking is great.

[@robertgad3269]

Excellent presentation (as always). This is going to sound like a quibble, and I don' mean it that way (after all videos can't be infinitely long), but I would add a section on headspacing straightwall auto pistol cartridges. All of the usual problems, but now add setting of your taper crimp. Too little: inadequate headspace and guns refuse to go into battery. Too much: excess headspace. May have failures to fire (light primer strike or no primer strike), and in extreme cases a kaboom from unsupported brass (particularly in some unnamed makes of auto pistols). Please pardon my well-intentioned "quibble."

[@kirkmooneyham]

I may not be an expert on firearms, but videos by Ian like this one sure have increased my firearms knowledge by a lot.

[@nicflatterie7772]

Old Lee Enfield rifles are notorious for headspace issues. At my range we have 303 gauges to check them. Old beat up 303 show up all the time and we have had some accidents. It’s now part of the service to offer a free quick check to shooters.

[@HarrisonCountyStudio]

5:04 great illustration

[@andrewgable7273]

Always nice for a review day. Spot on. I've seen head space set incorrectly. Wow!!!! Quite important to check. Thanks!!!!

[@greglaroche1753]

You didn’t mention about head space for rimmed cases. Thanks for the video!

[@uncleroysmusic]

Had a case extractor for my FN49...glad I never needed it. :) Excellent video Ian.

[@slayer8actual]

While in the Army I went to an armorers course to learn how to operate, maintain and repair many various weapon systems including the M2 .50 cal and M240 machine guns. The M2 needed to have the headspace checked whenever the barrel was installed which was a simple process and took less than a minute. The barrels of M2s were not assigned to a single weapon and were interchangeable between different machine guns, and because of that, the headspace had to be checked and adjusted. The M240 did not have to have the headspace checked since the barrels were assigned to that weapon by serial number. They were not interchangeable across different weapons. In our classroom there were some examples of machine guns mounted on the wall that did not proper headspace set. It showed weapons that had catastrophic explosions that completely destroyed receivers and barrels, and of course the instructors had stories of what happened to the operators of those weapons. The stories were probably made up but point taken - someone got messed up when those things exploded.

[@clydegrey5061]

Incredible video! You have outlined this super simply for us.

[@fortnex9972]

Just to tell you. You are followed from a guy of Argentina!!! Keep that great work!!!!👍👏👏👏👏

[@pstewart5443]

That case getting cut in half, that's a new way to fire form 350 Legens right there. Good job.

[@ColdPotato]

I can 100% confirm excess headspace creates fun. Had this with a 22lr upper I had where the barrel liner was not properly secured. What happened was I was shooting suppressed and did not realize that my barrel liner was ever so slowly moving forward. I eventually learned this when one cartridge blew out toward the back and made a boom that left my right ear ringing for hours, might pay for that in the future. Can't image what that would be like with say .223 or 9mm. Had to take it to a gun smith that epoxyed the liner in place. My guess is it was just pressed into place by the maker.

[@colinhugill9705]

There used to be replacement bolt "heads" for the Enfield .303 SMLE. From memory, they came with slight increments in length to adjust for headspace in heavily used rifles. The increments were around 0.001 (I think) and you could go up to three increments.

[@Haydn8oR]

Didn't know I needed this. Have an M44 Mosin that won't go into battery and haven't had the time to actually sit down and investigate. Gonna look into headspacing issues for it now.

[@TheRighttoArmBears2022]

Awesome video, I think most people that have guns no nothing about head spacing. Example people using 40 S&W in 10mm barrels, they will work but the casing is not supported properly.

[@onpsxmember]

@Forgotten Weapons Well done. I like those longer answers. I think you could quite quickly build on your vast knowledge with some technical drawing info. I get that it's ad-hoc here. If you go through 3-5 videos how cuts are displayed, outlines and not visible lines it can change not only further presentations but also makes it easier to spot patent changes to fool others or maybe how to make a cut away easier to understand in new books.

[@illegalclown]

Anyone else get that nice warm tingly feeling when someone says "trunnion?"

[@DevinMoorhead]

TRUNNION!

[@thenn869]

thanks for the explaination, I always thought it was the clearance or length before the bullet picks up the rifiling,

[@sammylacks4937]

Shoulda listened to Ian a long time ago. Ive always defined headspace as the amount of wiggle room that case has within the chamber. I know its more than that but in a nut shell that is headspace.

[@cristianpopescu78]

Great explaining! Thats why good quality ammunition is also required .

[@konstantin.v]

2:39 In your explanation why the gap being too small is bad *you contradict yourself* by later saying that the bolt is pushed flush with the chamber (anyway) by the recoil spring or by hand (5:01)