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.
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.
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.
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.
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.
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).
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).
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.
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.
Many thanks!! I really like your videos have been very helpful.
You are welcome!
Priceless! You've answered the question I always wanted to know but was afraid to ask ;)
Happy to help!
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.
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.
Thanks for sharing! 😊
I need to get one of those gauges 😉
Any time!
Fabulous information and explanation.
Glad it was helpful!
@@CopperStarPrecision You info is always helpful
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.
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).
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
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).