TriggerShims.Com

Rimfire Rifle Bolt Shim Index

Rimmed Cartridges use the thickness of the cartridge rim for head-spacing.
.22 Rimfires Headspace on the Case Rim, and the actual head space is in the recessed face of the bolt.
Generally Speaking there is extra room left in production guns between the Bolt and Breech to accommodate a wide variety of ammunition with varying rim thicknesses
You should first measure the depth of your bolt face pocket to insure it meets SAAMI minimum depth.
Shimming between the two bolt halves ensures the bolt is seating the cartridge up gently against the breech with your chosen brand of ammunition.
You can use our color coded numbered shims like a gauge to find the when the bolt face touches the barrel breech face, and then calculate where you want to be with your bolt headspace depth and rim thickness measurements.
I cannot tell you which shim best works with your rifle, you decide that yourself by fitting and feel and by shooting.
Installing Bolt Shims requires fitting by hand, and checking with the Bolt installed in the Rifle, and Locked Down - you do not measure with the Bolt out of the Rifle.
To establish the Bolt/Breech fit, shims are installed and fitted on an empty chamber.
If possible it may give you a better feel if you leave the extractors off some rifles while fitting shims.
Start with a 4 or 5 Pak of shims, install the .0015" or .002" thinnest shim and see how your bolt closes, if it seems to close as normal, then continue to install each thicker shim until the bolt starts to close harder than normal. At the point where your bolt begins to close hard, that was the amount of slack that was in your bolt, measured by whatever shim or shims combined were needed to bring the bolt up tight to the breech. Now it is best to remove that shim, and step back one number, example would be if a .005" Red shim causes the bolt handle to close harder than normal, then take it out and install a .004" Purple.
If you have to force or put undue stress on your bolt to close it, you should reduce the number of shims. You will generally only use 1 of the 4 or 5 shims in the package, but you can stack shims together if needed. When you have the correct shim installed, your bolt should close normally or just (ever-so) slightly tighter than normal. If the bolt closes slightly tight, it is best to back up one step, remove .001"
Put a very small drop of oil on the shim. Now you can go to the range and with the barrel pointed in a safe direction, once again check fit with your favorite ammo.
Due to variations in rim thickness, you may have to reduce the thickness of shims, remember you have already removed all the excess headspace from the bolt/breech, so now the only thing to do is remove thickness (shims) if / as needed to get to your sweet spot or required headspace for the rim thickness of your favorite cartridge.
For Longest Shim Life use a drop of oil or a (very small amount of) grease on your shim.
If you have to force or put undue stress on your bolt to close it, you should reduce the number of shims. A minimum of clearance should be maintained, while maintaining proper headspace. Do not put undue stress on the bolt by shimming too tightly as it is unnecessary!
At no time do you want to force the bolt to close, did I explain that clearly?
If you have any question, use a headspace gauge to check for proper headspace.
Bolt Shims have in many instances cured light strikes. Will they help with Accuracy? Don't take my word for it, Read our Customer Reviews or ask our Customers
Simply Chambering More Consistently Yields More Consistent Results.
Your Satisfaction is Guaranteed, if you feel you receive no benefit you may send your shims back for a Full Refund.

TriggerShims Bolt Shim Instructions Copyright June/2023

Click Here for ~ Everything You Need To Know About Headspace from Kurt the Gunsmith

V4/2024

The Match Chamber, and Rimfire Headspace are two different things.
Generally a Match Chamber is simply a chamber that is held to a tighter tolerance than a production rifle chamber using Premium or Match Chamber Reamers
A discussion of the Match Rimfire Chamber by Eagle Eye Shooting can be found here: (link) https://youtu.be/PzFCbOn_evE

The Chamber is in the barrel, and with a rimfire rifle, the headspace is in the bolt face. The bolt face is manufactured or machined to an average to function with many types of ammunition, both thick rims and thin, and the bolt is installed in a production rifle with additional space so as not to require hand fitting. Knowing how this works you can check and sometimes the bolt can be adjusted to better fit your favorite ammunition.

By reading and understanding the information and examples on the CZ page titled;
TECH TIP PDF: Measuring Headspace on your CZ 457 Rifle by Jack Behrman (link) https://www.triggershims.com/manuals/measuring_headspace_CZ_457.pdf
you can see that:
1) The Chamber is in the Barrel, and does not affect the Headspace
2) The Headspace is in the Bolt, and it's depth can be measured
3) The distance between closed Bolt Face, and the Barrel Breech can vary several thousandths of an inch.
4) The Bolt can be adjusted to move the face forward using shims, and the Barrel can be set back using a lathe, or forward using shims.

Conditions reported to us over the years by customers on different brands of rimfire rifles but specifically CZ Rimfire Rifles range from too tight and forcing the bolt face against the breech with excessive force, to too loose by as much as 0.006" or more. It is very simple to measure your Bolt Face Headspace using a Depth Micrometer, or Caliper, and then use our shims as a measuring tool to shim the bolt to touch the breech by feel.
See my LANCE'S TECH TIP: Rimfire Bolt Shim Installation ~ A General Guide ~ for more information
Using those two numbers, you can better decide what to adjust for best consistency with the rim thickness of your preferred ammunition. If in the unlikely chance your bolt is too tight from the factory, we manufacture Barrel Shims that can be used to address that problem on CZ rifles by moving the barrel forward. A much more likely scenario is to move a slightly slack bolt forward using our Bolt Shims.
It is a fact that if you more uniformly chamber your rounds, you can expect better accuracy simply through consistency.

Accuracy through Consistency - simply put production rifles have a large headspace to accommodate a wide range of rim thicknesses. Precision shooting involves eliminating variables for best accuracy, and using a bolt shim to adjust the headspace to fit a specific rim thickness better is all this involves.
The same principal used if you were to purchase a long shank replacement barrel, you would need a barrel shim to adjust for optimum headspace.

V10/2024

Bolt Shims In Production as of
December 18 2022

Bolt Shims Sorted by OD Size

1. .376 x .500 Ruger American Rimfire Rifle Bolt Shims
2. .376 x .565 CZ 457 Rimfire Bolt
3. .376 x .690 Orphan Bolt Shim Bolt
4. .450 x .565 Winchester 69A / 75S Bolt
5. .480 x .570 Remington 513
6. .357 x .595 Remington 540X Bolt
7. .442 x .595 Mossberg 44 U.S. Bolt
8. .450 x .595 Marlin 983 Bolt & Remington 504T
9. .500 x .610 Kimber 82 U.S. Bolt
10. .480 x .610 Mossberg 144 LSB
11. .532 x .640 Anschutz 54
12. .442 x .648 Ruger 77/22 Bolt
13. .480 x .648 Savage MKII Bolt
14. .500 x .648 Bergara B14-R Bolt
15. .511 x .648 Winchester 52 / Suhl 150 Bolt
16. .550 x .670 Tikka T1x
17. .570 x .690 Remington 40X Bolt
18. .595 x .690 Lithgow LA101 Bolt
19. .610 x .690 CZ / BRNO Bolt
20. .480 x .751 Walther KK500 Bolt Shim

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