Testing - Does Seating Depth Make a Difference?

[@gstyle2654]

Kelbly's is amazing! I'm a member at their range, and they are just downright good people. Family folks willing to help a stranger. I was in need of a little help getting a chassis fit on a rifle. Not knowing the"level" of what went on behind the shop doors, i approached with no expectations. Not only was i greeted with enthusiasm, but they took a quick look at my issue and disappeared with my rifle. I quickly learned details of what went on there, and I'm certain he could see the light click on in my eyes. He offered me a tour of the shop (which i jumped at the opportunity) and he showed me every step start to finish! Anytime i had a question, the guy performing the operation was proud to take a moment and explain. I've got a woodworking background, so watching them transform chunks of steel into a finely machined work of art was VERY fascinating! After my tour, we we're met back at the front office with my newly fitted rifle to chassis. I was then told there was no charge for the help. I wasn't raised that way, and left double what i thought might cover it. Simply down to earth, absolute good people!

[@hkenn8610]

This has to be one of the most top tier underrated gun-tube channels. I would venture to say that this has ultimate reloader beat, but it’s just my opinion.

[@hartfordboothe7466]

UR is a KZbin ho. This guy seems to have purpose in presenting thoughts and information.

[@stevenhavener7327]

OK, I knew I didnt know anything...... this confirms it !

[@newerest1]

Its just more proof that small sample sizes are misleading and if people don't understand why they need to dedicate the time to understand statistics

[@jcjustice3786]

Dang I don’t know didly.

[@roddecker1900]

Ok here 2. Can kind of understand John lott " more guns less crime" what i don't understand is if I can hole em 50% each in can I call that good .? I know : no ok WHY NOT? SERIOUSLY

[@rosalindstewart7013]

I’m confused

[@Gnolomweb]

@@newerest1 "shoot out your barrel to find the perfect load"

[@averagejoeshooting800]

I love this. I love that someone is doing these tests, I love how "in the weeds" this is getting. I love the that he literally says the exact same thing I say after nearly every range trip... "I'm left with more questions than answers. " I always felt like an idiot because I'd follow the instructions, I'd do the tests the way they say, I'd base my load on that data, load 25 more that same way, go out the next day and shoot completely differently. I'd ask 5 different people and get 5 different answers. I'm left wondering what REALLY matters... you ask a bench rest guy and EVERYTHING matters... you ask an f class guy and they think the bench test guys go too far, but they also measure the volume of each case because they're convinced that matters. Then you hear prs shooters say they don't even do seating depth tests because it doesn't matter THAT much... what can anyone believe? I want to do these kinds of tests, but I don't have the time, money, or equipment to do them right. I will be following this series closely. I love the hard data. I love that you talk about things like "standard deviation" and "statistically significant" data. These are terms and methods used by the scientific community to figure out IF there was a change, but also how impactful or noticeable that change is, and if their distribution is reliable. I took a statistics class in college, and I learned how to calculate all of these, but I have since forgotten. I'd have to pull up a text book to refresh my memory on the details, but I remember the general concepts, and this research is directly in line with what I learned. Please keep going with the same attention to detail.

[@95GTSpeedDemon]

I'm the guy who have shot a one-inch Group at 100 yd what happened quite happy. I tested some different ammo and saw that some ammo just shoots better than others. I started measuring stuff and then started testing. I saw that there was some noticeable tightening of groups. I decided to buy a good Barrel. Repeat it the same tests and saw that the good Barrel basically mirrored the same thing except the groups were all tighter. I did a powder test at the same seat depth, one bullet each and did two sets of tests that way. I recorded the Target so I knew what was hitting where. They all shot good but what I found was a little bit lower than Max seem to hit in the same area before it started to walk point of impact. I took a powder charge that was on the top end of what I thought would still group okay. All I did was load them .04 longer. Made a big difference. I have never shot a .34moa group before. I was now beginning to see how I shot the rifle would make a difference in the groups, where as I would never know before

[@MDavenport-p2x]

Í

[@emmettdibble8404]

Thanks!

[@winninginthewind]

Thank you!

[@fosterprice5690]

Hello from down in New Zealand. I've been watching your videos for a long time . . . . This one is among the most usefull and profound you've produced. Thank you!

[@toods2]

This really was quite fascinating. Thanks for the video.

[@oscarduyvestyn7969]

Thank you for sharing Keith. I love the way you apply science to your testing and show the importance of statistical significance.

[@lennyfoffa5971]

This is one of the very best Shooting / Loading videos ever produced. Pure science without bias toward any Caliber / Rifle Mfg./ or Bullet Mfg. Love this Thank You. Lenny

[@lasserastad]

No ads! What a legend :D Great video also!

[@britishbulldog8966]

More questions than answers usually means that you’re on the right track. The world is vast and infintismally small. Isn’t that great? Excellent video.

[@McgSpook]

Great work! This is exactly why my 100 yard stuff is just to get some "maybe" loads. Then hit 600 for testing/fine tuning and eventually 1k tuning. What's really fun is sometimes my 600 best load and my 1000 best load aren't the same... How fun is that? Ultimately there is always just a bit of voodoo involved due to how many variables exist. Love watching the channel and seeing the science behind the magic.

[@DocJustinT]

This is fantastic! It reminds me of my Ph.D. dissertation where the conclusion was (paraphrasing), "the math works, the process works, but it's just not efficient and no one knows why." Granted, that was for a couple electrochemical reactions to convert molecules from oxides to hydrides... but I totally feel the pain all over again of having more questions than answers.

[@JustinMiales]

I had PhD once I tried everything to get rid of it but no matter what the doctor gave me didn't work, then it went away over time

[@longlowdog]

Wow. Now we have to contend with Group Center Wander. 30 years as the nut behind the bolt and I was oblivious on a conscious level to this. Thank you for the time, money and effort you have spent on this test.

[@robertgore9449]

Even when I don’t understand all of what you’re talking about I find it interesting and entertaining to watch. I do learn a lot though, and as a new precision shooter and one who’s reloading, thank you for doing things I would never even think of.

[@Deerslayer1912]

Things I can confidently take away from this video: your gun shoots very well Load development always reminds me of this quote: We have not succeeded in answering all our problems. The answers we have found only serve to raise a whole set of new questions. In some ways we feel we are as confused as ever, but we believe we are confused on a higher level and about more important things.

[@MrMillez]

Thank you. I’m relatively new to reloading. Knowing I’m not the only one trying to work this our help a lot.

[@josephehrlich6400]

Love your videos and your scientific approach!

[@traviscovey1602]

Great video! Thank you for the work you put into these videos!

[@htchtc203]

Thanks for interesting and honest review of the test. A little statistician in me says that three shot group tells very little if anything about differerences between loads.

[@stephent2243]

This has made the inconclusive seating depth test I did yesterday, more inconclusive haha. Joking - I really enjoy your content.

[@Okrifleman]

Great video. I’ve decided if you pick a good bullet with an appropriate powder you’ll be fine. With big enough groups things start to look a lot the same.

[@davidschmidt5810]

The key to load development is to not put too much emphasis on any one or two stats. That tiny group at 100 yds for 3 or 5 shots may not tell you much at distance. Thanks for taking us down the bunny hole with you Keith!

[@willo7734]

Really outstanding testing there. I’m glad that somebody out there is thinking about group size and statistical significance. These days I don’t worry too much about seating depth as long as I’m shooting hybrid bullets. The main thing I do when reloading is make sure that the seating depth is as consistent as I can make it. My personal thought is that variability in the seating depth is way more significant than the actual depth itself.

[@redrock425]

Exactly, repeatability throughout the whole process is key, right up until and just after the pulling of the trigger.

[@kc8omg]

Fantastic video, greatly appreciate your efforts on this one and the great break down, even if there weren't any solid conclusions.

[@RetiredSkeptic]

I guess the big question is; at what point do you stop splitting hairs? My answer would be, when you stop having fun. I love seeing the research because someone else is putting in the work. Great analysis, and I concur with your conclutions.

[@randomidiot8142]

It's competition. You stop when you win and when the competition stops trying to beat you.

[@TheIncredibleMrG777]

Thanks for sparing us the ads👊🏻

[@quarterminutemagnums]

The more I learn, the better golf looks...............!

[@mikebeddingfield2144]

😂

[@barryweaver6834]

I’m sorry but I’m going fishing instead. Golf sucks! In fact a golf course is just a major waste of hunting woods or range property

[@WyloSuggs]

"Instead, I have generated more questions than answers" Pretty much sums up my decade of experience with reloading

[@hartfordboothe7466]

There are too many variables to make reloading truly scientific. I, too, have been reloading for a decade and I gave up on the competition shooting thing in short order when I realized this.

[@newerest1]

Thank you very much for this valuable research.

[@bobbywinn6548]

Thank you for sharing!! Also, thanks for detailed explanations about the testing format.

[@jeffsiewert1258]

Mean point of impact standard deviation is equal to the true dispersion divided by the square root of the number of shots. Since dispersion is the result of random processes, there’s nothing you can do to make the mean point of impact “more stable” except make the groups smaller..

[@8208isfun]

Great video. Thanks for explaining and proving the sample size that we need to be working with.

[@prebaned]

Without reinventing the wheel simple ram and cram work best for me. My experience was best to neck size only to max .001-.002 tension, load longer than the lands, then single feed in my 700. The caming of the bolt insures the case shoulder is against the chamber datum line case to case same, and the bullet "jump" is zero insuring exact same cartridge to cartridge without calculating throat erosion. Works for me and simple consistency...

[@copperheadroad567]

You sir, just earned yourself a subscriber for all the adherence to the fundamental science of testing. Excellent integrity and looking forward to seeing what you’ve got cooking up over this next year.

[@johngreen2451]

Having shot silhouette competition for years I've found that some cases will not shoot. Therefore after I have prepped all of my cases I go to the range and any round that shoots outside of my group goes into my junk brass. I've shot many 1/16 inch groups following this procedure. I feel the brass is the most important part of the reloading procedure.

[@Reloadingallday]

Awesome video, keith!

[@TyroneNorthcutt]

If you could have seen the smile on my face when you said, "We are closer to proving they are all the same, not different". Nature is perfect, nothing else. Some think 1ft is close, some 0.25", others won't settle for less than 0.001" and most who state, 0.0004" might be accurate in what something should be, but they have no clue how to measure, (guarantee) it. Or worse, you see a shaky table with a Starrett Vernier Height Gage. Tolerance is as misunderstood as monetary policy. In other words, everyone is an expert, (at spitting the rhetoric), until it isn't. (Argentina, Rome, Japan). Much respect for what you do, so refreshing to see people taking things to the nth degree. "If you torture the data long enough, it will confess", but unicorns still don't exist. Try, test, break and prove. Don't vehemently spit rhetoric from other sources. If I haven't done it, tried it, lived it, built it, broke it, tested it, everything else is hearsay, rhetoric or logical fallacy. TEST, TEST, TEST, question the data and RETEST, RETEST, RETEST. The goal of science is not to find a final answer, but to ask better questions. long time subscriber... Great content, please keep it up. Will try to be better on the likes, sorry. (.284 fan, 7mm-08 and 280AI)

[@stephenbaker7499]

So well said sir.

[@berra_the_shooter]

Great video! The number one most important thing to me when im doing seating tests is windflags. To me its pointless without.

[@claytontarics4521]

Thank you patrons!!! 🎉🎉

[@MKChase-uj9vx]

New subscriber. all the best from the UK

[@GalloPazzesco]

Okay, let's do this. Subscribed, bell rang, commented, liked, upvoted, shared .... may the algorithm gods smile favorably upon your channel.

[@Eric--zs6um]

Great channel to follow. No bs.

[@BigTimberLodge]

I am a scientist and appreciate your hypothesis and the fact instead of definitive answers you created more questions. Isn't science great? LOL, good job

[@niuhikona]

Always great content, thank you.

[@newerest1]

The numbers are science if you ask me. They are controlled enough for me to find the testing valid. The only question is the question of repeatability. I assume that if we were to do this experiment again a second time, (which I would love for research purposes of course) that the small sample size groups would have completely different results because of the small sample size variability. I also believe that the large 33 shot groups would probably be quite similar.

[@ljolik2000]

good explanation! somehow I missed your genial diagram with grouped box plot with ED SD and average values for each depth.

[@thepracticalrifleman]

So we discovered consistency matters most.

[@salparadise5448]

Always the same. You discover a new hobby/ topic. You start to learn. You consider yourself as an expert. And then you realise that there are millions of other things you don’t know.

[@briansteele1378]

Another variable people often don't think about when measuring group size/mean radius from the center of the bullseye or the corner of the square for this instance is that I can almost guarantee the crosshairs were not in the position you are measuring from when the shot broke for every single shot. As steady as you can hold the crosshairs on center, there is going to also be variance from that which is typically not accounted for.

[@winninginthewind]

Yes, that is a good point. Shooter performance is an expected source of noise in a test like this, just like conditions are.

[@Mafiaal1]

I recently was testing the speers grand slam in my hunting rifle, the speers data listed a seating depth of 2.685, i could not get these to group, we're talking 3-4 inches at hundred yards. In a last dig effort i measured these bullets to my barrels lands, which was 2.848, this was such a huge jump that i loaded them to 2.775 and got them to group sub MOA with two different powders. Seating depth plays a huge roll. IMO

[@michaelmoffit1423]

Also, bullets are different and will shoot distinct patterns depending on how they are made. Lead tamp just a liftle off center and you will get 3&2 groups. Boatail off a bit. 4&1 groups. Point being, you are holding the bullets as a known constant when they are not, especially at the differences you are trying to detect.

[@cav4353]

There it is. Combine that with tiny differences in ogive and jacket thickness, as well as atmospheric differences from the previous shot, and minute amounts of equipment wear. Now at least I have my excuse.

[@foubert45]

Biggest thing you’d didn’t mention that you have to consider is variances in case head space and case trimming which has a large impact on seating depth depending on the dies and case trimmer you use.

[@rotasaustralis]

How does case trim length effect seating depth? The C.O.A.L is measured from the case base as is C.B.T.O. Headspace is what it is. Everyone seems to be able to get it +/- 0.001 which I don't think makes much if any measurable difference. Even if we could measure the difference, there's nothing to be done about it anyway.

[@randyemenhiser2573]

Great video - fun and interesting stuff!

[@GetMeThere1]

I'm very glad for this type of work. Thanks VERY much for doing this, and for sharing it. My question, however, is even more fundamental: Is it even POSSIBLE (just mechanically, but also OPTICALLY) to point a rifle at the same spot on a target 100 yards away within, let's say, 5-10 thousandths of an inch? And, how could we test THAT question? Watching hunting channels lately, for example, I've heard from some that points of aim (optically) can vary considerably depending ONLY on the precise angle to the sun one is aiming at.

[@oliviabalch3144]

Keith , great video I’m a friend of Michael’s who you mentioned. I don’t understand why you say the group center shifted , I think it is much more sensible to calculate the relative center for each load then take all data from there it just streamlines the result. If you only look at it that way I think the data will show the statistical samples are indistinguishable.

[@winninginthewind]

You are correct. No matter which group center I use, there is nothing statistically significant about the very small differences in the samples that cannot be the result of random chance. The moving center is a concern for long strings of fire at long range. It is easier for the shooter to correct for wind conditions without group center movement, but even that observation was only an anecdotal one. A lot more testing would be needed to clarify and validate this as a behavioral pattern.

[@peteivanthomas]

Yes, it's just another form of being fooled by random noise in the data. Load development/tuning beyond a certain point may be a myth, and we are just engaging in voodoo based on noisy samples.

[@john-draftanimal]

Nice. As a scientist often employing statistical analysis on small and large data sizes I love this particularly your statement about your lack of significance in proving a difference from the null hypothesis. One might assume its for a lack of power or data size but perhaps not as the distribution shapes in 2d are quite different. Thank you. Your experiment here seems to assume that for each loading you actually achieved the same seating depth for each round. If you could have I'll bet there is some movement there and differences in variation vs your different target depths, meaning I'd expect greater variation with deeper seating depth. . I'll also bet on variation in seating neck tension?. How precise are your depth measurements and inside neck diameter? With different distribution shapes, standard statistical models may struggle. If you had the data of high precision seating depth one could plot vector values angle and distance from center vs that. Probably out of scope though.

[@joearledge1]

Run the median values(median radius and median group sizes and appropriate SD and ES)and see if the story changes... and an ANOVA test. In all my research lab experience, when sample sizes were low, median values were the way to go because they are resistant to outliers, good and bad ones. Anyway you slice it 33 holes is a small sample size out of the total "population". Not a dig at you, it's more than most people do, and reality dictates that unless you have someone feeding you time, money, components, and barrels, getting legitimate large sample size of everything you want to test is not even close to practical. Anyway, try the medians and anova on what you already have, thanks for the info and keep up the good work.

[@nathanbailey9153]

The biggest problem is with "proper" large sample size for cartridge load tests is the limitation of barrel life, and the fact that the barrel's behavior changes over time. There is a sweet spot after proper break-in and before accuracy fall-off that is probably not-quite big enough for a single proper large sample size. So any large sample size tests can only be a single run of a single variable on a single barrel. And that is essentially meaningless if we want to compare two or more options. So we are stuck with smaller sample sizes if we want to compare two or more options.

[@joearledge1]

@@nathanbailey9153 yeah, that's pretty much my point. You run into similar stuff in research labs. Where, due to the nature of something or something beyond your control, or practical constraints, you're gonna have small sample sizes. The way we delt with that was median values and anova tests. Sample median usually approaches the true population mean, before the sample mean does. This is because the median is resistant to outliers, and the mean has to have a sample size larger enough to overcome the outliers.

[@garrytalley8009]

It is a constant challenge trying to be better especially when you almost have it down. Nothing seems to be a 100% constant in reloading. Most everything can change group size and when you change one thing it is more than one thing. Bullet length effects case capacity as well as bullet jump or jammed in the lands. Have fun to all there are always more questions than answers. It's always fun seeing what others are trying and what works for them.

[@truegret7778]

Sounds like a task for having a very good understanding of statistical process/quality control - Tagushi Methodology. Taguchi methods are statistical methods, sometimes called robust design methods, developed by Genichi Taguchi to improve the quality of manufactured goods

[@W5rr2nG]

i was looking for this video. I have a suggestion. maybe try this again with the best and worst powder charge from the initial workup. but i enjoyed this. new subscriber

[@fgutie35]

I'm not by any means, an F-class shooter, but I would venture to think that bullet jump plays a roll in how concentric the bullet is going to be when it hits the rifle lands. The farther the jump, the more the variance. When I reload, I measure and weight every component and group them to the least variance. Also I seat bullet to slightly touch the lands to eliminate bullet jump. That has given me great results.

[@DanielReyes-hz1qk]

Be careful with this, for as the throat of your rifle erodes that slight touch will become a slight gap; you'll need to adjust your length regularly to maintain what you've got

[@CacheCropp]

Slightly touching is the most erratic seating depth you could choose. If the CBTO is .001 shorter the pressure spike will be wildly different than if the CBTO is .001 longer than normal. Not good.

[@scottcrawford3745]

@@DanielReyes-hz1qk Erik Cortina, current world F-Class champion, states in a full video that "chasing the lands" is not the key to accuracy or consistency. His concept is that you are trying to achieve a consistent pressure-curve within the case and post-ignition barrel volume for every shot. internal case volume ( loaded) depends on an accurate powder amount and an accurate bullet base position to ensure identical ignition. Initial seating depth is mostly to see what gives the best overall basic accuracy and will function in the action.. After that, you keep that same seating depth for the life of that barrel, all other components being equal and identical.

[@DanielReyes-hz1qk]

@@scottcrawford3745 I'm aware of that, and have seen the video. But that doesn't apply to the person above using a load that just touches the lands; that pressure curve is going to change dramatically the moment those rounds no longer touch the lands. He mentions this exact scenario, if not in that video then in another

[@scottcrawford3745]

@@DanielReyes-hz1qk The Number 2 guy in the world uses a .020 jam into the lands as his seating length... not sure of the pressure game he's playing. My bullets are Hexagonal Boron Nitride coated, So I have a little more leeway with friction vs. jump than some. If you're watching your brass/ primers and paying attention to the signs, I'm sure it's reasonably safe, as long as you're not at the very threshold of max pressure. After all: they only need to punch paper.

[@gold_3]

Great video, thank you Sir👍

[@judahparker9684]

I’d love to see this test performed on a standard hunting rifle. My guess is that a competition heavy barrel has less variation overall, while most of us are doing load development for hunting rifles with pencil barrels.

[@cecilandrews7479]

Seating dip does make a difference in your group sizes. And some projectiles are even more finicky than others. Like the Hornady ELDM. I have a load with them that will shoot half inch groups in all three rifles but not consistently the r is the only one with that load consistently shoots under .500 Raffle one ar10 width 18 inch 1/10 twist. rifle 2 Remington 700 width 24 inch heavy varmint 1/ 10. Rifle 3 Ruger precision Factory. The berger hybrid didn't seem to care. So the reality is one size fits all, doesn't exist

[@chrishill1286]

I have a Ruger77 MkII in 300WM. At best with factory ammo 2 MOA maybe a tad under. I loaded 20 rounds Starting at factory dimensions and did 5 groups .005" steps and found the sweet spot thankfully in my third group a full .015" longer than factory. I'll take that experience to the bank as the simple hunter that I am.

[@johnm8891]

I would like to see testing like this done with a medium contour hunting rifle where barrel harmonics are a much bigger factor.

[@sharpandloud3422]

“I have generated more questions than answers” might as well be the slogan for hand loading in general. Nothing beats practice time behind a good barrel, period.

[@charleshetrick3152]

I miss the Biden Harris ads that usually bracket my favorite firearms KZbinrs. I do love irony.

[@adamjones7497]

Just keep in mind, under the Biden administration, NFA approvals are the fastest they’ve been in 15 years.

[@conunpocodefe]

I wish that I had Harris Biden ads. All I get are machine gun arcade games! "We grab the Kalashnikov perfect choice." Thank you for ad free videos And I like the 7 to 9 minutes videos as well as the deeper dives.

[@thepracticalrifleman]

I was thinking more about this overnight. I wonder…we know the Hybrid is a relatively tolerant bullet. It’s why we like it. However, how does barrel wear play into it? How about bullet variance? Lot to lot variance? With so many variables, could regression analysis be helpful in determining where to place our focus?

[@rickschwertner282]

Now to perform the same test at 1,000yds. I really liked this video. I did a similar test with only 2 loads at 1,000yds and 20 rounds of each load with my 223 and the smallest 100yd group was not the winner for sure.

[@dedon03]

Bullet seating depth and free bore seem to be the reason why one another are hot topics. If you get the free bore you desire at that point should it just really be at the mercy of powder primer with a constant being the published seating for the load in the reloaded bible?

[@Narcissist_Police]

In my experience seating depth has very little improvement to precision. Depending on your objective will determine if it’s required to test. You have to constantly change the seating depth due to throat erosion.

[@stevenmarcus2709]

The nearest thing too factual testing we have is from hornady but they’re obviously using Hornady brass and bullets. I know from experience that the components aren’t precise enough too even show a difference in small adjustments too the load. I want too see Capstone or Berger do some large sample size testing.

[@swampysanta5445]

i found out over the years reloading bullet seating around what the bullet manufactures tested at always did better then seating closer to the lands

[@MMBRM]

Just for curiosities sake did you collect velocity data during this test? It might be interesting to see if there are any correlations there. It would also be helpful to know how much the seating depth varied by for each set. As at this point it seems reasonable to think that moving the seating depth 0.001" for each test would show smaller differences than moving it 0.010". I think it would be more helpful to first prove that seating depth makes a difference then move on from there.

[@roddecker1900]

I watch his videos cause I like to and xpect to pick up somthing. Q/ public assumes some things are the same as q had going in . I dont think he said he WAS looking 4 something specific.

[@MMBRM]

@@roddecker1900 He was literally comparing three different seating depths to see if they generated a statistical difference within 33 shots at each depth. He didn't have a pre-determined result in mind but he was definitely testing a specific thing.

[@chuckallen9778]

I see that I'm not the only one that has more questions than answers after a trip to the range. Tho sometimes I need a yardstick not a caliper to measure my groups.

[@JakeElliott-f3j]

Hey Keith, quick question: how "far apart" were the 3 different seating depths you selected for your testing? At 5:25 you asked if you "can do seating depth testing in much bigger increments" and I'm just curious what the total delta CBTO (in inches) was for your 3 loads?

[@winninginthewind]

Load #1 was .009" from load #2 and .015" from load #3.

[@SCBCo1]

A serious question from a beginning precision shooter. “The first shot” or cold bore shot. Is the difference the heat of the barrel or a harmonic resonance? If its harmonics, has anyone tried to create that same resonance artificially in the barrel prior to the first cold bore shot? Or, heat the barrel prior to the first shot?

[@MMBRM]

What people call cold bore is normally actually a few different things. MOSTLY it comes from clean bore. What I mean is that there are still some solvent residues inside the barrel which are cleared out with the the first shot. Also a completely clean barrel has a different friction profile than a fouled one. Most of the time you will even see this on a chronograph and the shot will be slower. Now if the barrel hasn't been cleaned this effect is typically lessened. However, when you take your gun from a warm dry house and bring it out to a wet humid day condensation will form inside the barrel. The first shot once again has to clear this out. The amount of heat transferred into the system after a single shot is very low because of how much steel there is to soak it up. So temp itself is likely one the lowest of the factors. So generally a "cold bore" shot is generated by internal barrel conditions. The "harmonics" of the barrel isn't changing between the first and second shot.

[@SCBCo1]

@@MMBRM Thank you for the explanation. The class I went to by a former sniper mentioned that he never cleaned his barrel but I should have asked why. Thanks again.

[@MMBRM]

@@SCBCo1 You will get more consistent results in extreme precision/accuracy by cleaning the barrel to bare metal every time you shoot it and taking 2 fouling shots before you start. Simply stated you can be consistently clean but you can't be consistently dirty. However, if the situation requires consistent first round impacts with no option for sighters/foulers then you may be better off cleaning less often. However, you will reach a point where the fouling negatively affects accuracy because it changes barrel dimensions and the copper deposited on the lands can shear more copper off the next bullets. You can usually lessen barrel fouling for its life if you clean very well and make sure to remove all the copper with a bore paste for the first 50-100 rounds. You'll need a bore scope to verify it's gone.

[@MrT13]

Yes it does, if you don’t have a barrel weight/length harmonics adjustment. Both is best.

[@lizchatfield692]

Hi do you Chronograph each round you fire to see if there is any difference in velocity.

[@coreystock5361]

Absolutely fantastic.

[@ericrumpel3105]

Thanks fer sharing, you are an innovator fer sure, unlike the johnny-come-lately-looneytooner dude who is merely a follower & calls people stupid for past innovations.Thanks for your generosity to those whom are less innovative.

[@michaelmccormick8562]

More questions than answers........the same result i get any time i test. Good video

[@CacheCropp]

Even though no actual jump numbers were given in this video, it sounds very similar to Mark Gordon’s study from a few years ago written about on the Precision Rifle Blog. It seems to confirm that the micro results of best 3 and 5 shot groups don’t match the macro results of consistency of group size and POI over a larger sample size. Typically a bullet jump of .050 - 0.100 yields better large sample consistency even though .010-.030 might give you tinier 5 shot groups.

[@williamsweet7511]

How much did air temp change during your test,barometric pressure, your load, powder type, etc… there are many things that are controlled but are they? Was there a small breeze? Did one bullet have a small deformity? The brass, was it new or how many firings? What primer type? Seating depth of primers? Did you clean your barrel between each firing? I know you know all of this? I’m quite impressed with your test and attention to detail, as well as your analysis of data seems on point. But in theory you’d have to repeat the whole test 30 plus times which is impossible under the same conditions.

[@cornydad]

Thank you

[@mdtnak]

I struggle with the use of SD on data sets of less than 30. Is there any reason why we are not using a two-sided tolerance interval with something like a 95% CI, 99% proportion and evaluating at least 10 values? TI is better than SD when working with samples sizes of < 30 and gives a more reflective outcome. BTW.... just found your channel, and appreciate the information you are sharing.

[@geordiegeorge9041]

Thank you.

[@tommycater5239]

Id imagine its possible that the data could be more determinant at a farther range? Say, 600 yards? I only ask that because im finding that developing a round to group, say, 1" at 100, can be done easily, but that rounds performance at 500 yards could be the exact opposite. Basically just thinking outloud here. I will add for context the reason i ask that question is because im finding that a projectiles bc under 200 yards, for hunting, is negligible based upon caliber. I just wonder if this test was conducted at 600 or 700 yards if the data would show something different? Thank you for what you did to make this video. I really appreciate it

[@eamieva02]

What video is the one where you mention diferent bullet profiles and the seating dept that they favor?

[@Archer300wm]

Have you tried the Hornadi 180 eld-m bullet? does he have a higher BC than Berger 180?

[@deano6874]

Outstanding video! Thank you sir! Liked & Sub'd.

[@congerthomas1812]

Crimp pressure also!

[@suidafrikaanseboer3320]

What is the name of that vise or stand you use to shoot from.

[@boony853]

A recommendation: consider performing a 2-way ANOVA since there are factors that could affect another factor, ie: barrel temperature with x.

[@alewis1927]

Did you allow the barrel to cool between shots or strings? What was that protocol?

[@winninginthewind]

Cool to a barrel temp of 90 F before resuming firing.

[@MrBoostin18]

First of all I’m a firm believer in seating depth doesn’t matter, but only if you are using hybrids and tangent style projectiles. Things to remember. He was using hybrid projectiles. Which Litz has stated in his science is not affected by seating depth as much as secant/vld profile projectiles.

[@MMBRM]

What method are you using to decide if they are significantly different? There are some arguments to be made that a T-TEST may not be valid because since group size should follow a random normal distribution that SD shouldn't be weighted in deciding whether or not they are from the same population(as the T-TEST does). A T-TEST would say that two sets of 5 x 5 shot groups that happened to have a smaller SD(size) when compared to another 5 x 5 with the exact same average size but which had a higher SD that the lower SD groups were statistically more different than the higher SD groups but that SD difference is just due to the random group size range of a normal distribution. Since we can only expect to predict the size range of the next group not the exact size itself.

[@michaelmoffit1423]

Mostly ditto

[@BestKiteboardingOfficial]

Seems like you have to shoot this indoors, with a fixed mount and maybe look at barrel temp effects at the same time.

[@winninginthewind]

That is the conclusion I came to. Outdoors, even with flags results in too much confounding variance. The downside is that there isn't a rifle capable indoor range within 1000 miles of here.