CZ 457 MTR Measuring Headspace

[@douglassnyder1292]

Thanks for making this, and doing a good job of it. I just ordered some bolt shims for my CZ455 and will be addressing this subject soon. This was very helpful and simple regarding the measuring points. I am new to the shimming world and am looking forward to seeing if it makes a difference. One side note: The 455 bolt is very easy to disassemble/reassemble, which will make field changes of shims a breeze.

[@CopperStarPrecision]

Glad I could help! In my limited preliminary testing I have found that matching headspace to the rim thickness of the ammo that you use helps with accuracy by increasing consistency of the firing process. My CZ 457 likes to be at or just tighter than the rim thickness. I mainly use SK/Lapua ammo which is around 42-43 thou rim thickness so having a headspace shimmed to 41.5-42.5 thou has given the best results. Any tighter and the bolt becomes difficult to close. Eley tends to be thinner in the rim and something in the 39-40 thou range works better than my rifle's default headspace of 43.5 thou.

[@fedorg7985]

Priceless! You've answered the question I always wanted to know but was afraid to ask ;)

[@CopperStarPrecision]

Happy to help!

[@billteat124]

Many thanks!! I really like your videos have been very helpful.

[@CopperStarPrecision]

You are welcome!

[@joea4998]

Thanks for the video you cleared it up better for me. I have a lilja barrel coming in this week and will need to do this. Also nice base class build I just jumped up to open this year but will be keeping my pro varmint as a base class gun after nationals next month.

[@CopperStarPrecision]

I think the Lilja prefits come with a 1.200" shank length with barrel shims. If you know the bolt face to action face distance you can set the headspace to the ammo you plan on using. Next video will be about measuring rim thickness.

[@fredshebester-wg4vb]

Fabulous information and explanation.

[@CopperStarPrecision]

Glad it was helpful!

[@fredshebester-wg4vb]

@@CopperStarPrecision You info is always helpful

[@CountryRimfire]

Thanks for sharing! 😊 I need to get one of those gauges 😉

[@CopperStarPrecision]

Any time!

[@johanneslaxell6641]

I need to find more info. I don't get how when the cartridge is in the chamber the headspace comes into play. It's lengthwise so I just don't get it...

[@CopperStarPrecision]

Headspace measures the gap between the bolt face and the edge of the chamber when the bolt is closed. If you have headspace that is longer than your rim thickness, then the firing pin must push the cartridge forward until the rim makes contact with the edge of the chamber before setting it off. This small amount of play can cause inconsistency in ignition timing, which can lead to inconsistency in accuracy. If your headspace is smaller than the rim thickness then you are crushing the rim. This can lead to a stiff bolt close. The goal is to match headspace to the rim thickness of the rounds that you want to use. Laupa/SK generally has a thicker rim than Eley ammo. You want a headspace that is exactly the same or ever so slightly less than the rim thickness to make sure that the ignition timing is as consistent as possible shot to shot. Hope that helps.

[@johanneslaxell6641]

@@CopperStarPrecision Yes, that helped, and I thank you for that 👍🏼. Somehow feels like 3D-scanning and measuring of the cartridge would be as important but that is probably "overkill" 😆. I'm just interested, I don't even shoot precision target. Just hunting. Be well and take care 👍🏼🫡🤗.

[@skipsmith9692]

If you measure this and find that the difference does make a difference in accuracy do you then batch the ammo accordingly? Then if so would you make the changes with bolt shims verses barrel shims for a quicker fix? I have heard this for years and I have even when loading for high power competition we would weigh each bullet, case, etc. to all match our desired needs. We did see a difference in our 600 yard shots…not so much on 300 in.

[@CopperStarPrecision]

Weight sorting is difficult with rimfire since you don't know if the source of the discrepancy is due to the case, projectile, powder, or priming compound so I don't bother. For competition I try to stick to the match grade ammo (Lapua Center-X, Midas+, SK Rifle Match, Eley Match, Eley Tenex) which has shown to have very consistent rim thickness across a box/brick/case. I do not yet sort by rim thickness, but might start doing so for my benchrest rifle, not my PRS/NRL22 rifles. Where I do see some potential (I am still testing and will release videos when I have conclusive findings) is to match the headspace to the rim thickness of the particular brand of ammo that you intend to use for competitions. Bolt shims decrease headspace and Barrel shims increase headspace. With my headspace of 43-43.5 thousandths it is well suited to the Lapua/SK brands. I see some marginal benefit to adding shims to get the headspace closer to 39-40 thousandths when using Eley ammo (still testing this out).

[@billteat124]

looking at the prs basic class, would you recommend the cz 457 or the ruger precision. have not shot this dicipline before. many thanks Bill

[@CopperStarPrecision]

9 out of 10 of the top production class competitors from last year's finale were using the CZ 457 MTR. I think any CZ 457 that fits you well would be the way to go. The MTR at $849 MSRP and the Bushnell Match Pro ED at $749 MSRP puts you just under the cost cap for Production class for PRS Rimfire and is a killer combo (but it will put you in Open class for NRL22).

[@ryanmckee2089]

Do you know if there is any truth that the MTR is head spaced for Lapua? I want to measure head space on my MTR but have to get the proper tool for the job. Modifying these things seems never ending. lol Chasing that elusive group is so much fun! 😂 What group sizes are you getting at 50-100yds?

[@CopperStarPrecision]

I only have a sample size of 1, but mine headspaces at 0.043"-0.0435" which is consistent with Lapua/SK ammo. Eley rim thickness is usually closer to 0.038"-0.039". My MTR really likes Lapua/SK products, especially SK Rifle Match. It shoots Eley like crap. Other people with CZ457 have had similar experiences. 50 yard 5 shot groups on a calm day average 0.25" with my best group being 0.181". At 100 yards I'm averaging 1.25" groups. Velocities are around 1070-1090 depending on temperature with SD of 6.7fps. This is with ammo I have been able to source locally. Eventually I will get it lot tested at the test center when I can save up enough money to buy a case of ammo.

[@ryanmckee2089]

I haven’t been able to shoot much of anything consistently. Eley Match shoots well actually, when I can do my part and I don’t get a lot of fliers. I’ve got some Center X that shoots alright. Probably could do better if I take my time. Bought a bunch of Wolf Match Extra to try out for plinking ammo basically and a brick of SK Rifle Match on the way since I’ve shot only a handful of them since I’ve had my rifle. Getting match ammo around here is impossible. Online or a few hrs drive anywhere, to get it. Currently waiting on the Pete’s Pillars cocking indicator and upgraded/reshaped firing pin. Hoping theyll help somewhat. Can’t wait to get out and shoot this weekend! I could talk about this stuff for hours, obviously. lol Enjoy your vids and am learning a lot about these CZ’s.

[@ryanmckee2089]

I would love to get into some BR comps if I could ever find any in my area and can get my groups respectable. Really need to start trying different ammos and lot testing. There are so many variables to getting accuracy out of these things it seems never ending, but a lot of fun!

[@joed3264]

@@CopperStarPrecision My friend Bill Calfee states that good ignition is more important than headspace.

[@joed3264]

That is the hard way to measure headspace. I have 4 headspace gauges - .042, .043, .044 and 046" I run my CZ at .043".

[@_JimS]

If you use the other end "Jaws" of the calipers it would be more stable, "step measurement". Finding the Step Measurement with Calipers, a slightly more complex and lesser-known technique, step measurement can be very useful for a variety of measurements. Start by placing the sliding jaw of the caliper on the upper step of the object you are measuring. Leave the caliper just slightly open. Slowly begin to open the caliper further until the fixed jaw hits against the lower step of the object. Then read off the measurement and voila! kzbin.infoagSgARJb9TU?si=4bMbbi6-kZsYL2pH

[@CopperStarPrecision]

Very true!