So, want better and more consistant accuracy from your Rimfire Rifle and / or Pistol.
There is a pretty easy way to improve both and that is to sort your ammo by Rim Thickness in various grades of thickness of the rim. A Rimfire is Headspaced on it's rim and as the thickness here can vary somewhat it affects overall accuracy when the cartridge sits in the chamber at different depths and / or position from the Bolt Face. Keeping this constant through a number of rounds helps a lot with accuracy and reducing that crazy wild flier that seems to creep into any group.
Target shooters do this measurement but it will help with any form of shooting a Rimfire even hunting to know you can be more consistant with your point of impact.
There are various Gauges you can buy to achieve this measurement and costing upwards of $70.00 or more but one can be made fairly easily from a fired .22 calibre centrefire cartridge. My method is just one and depends on the equipment you have at hand but start by finding a fired .22 calibre case that your Rimfire Ammo will slide down the neck of easily. Do not size the case but remove the spent primer so it doesn't interfere with your measurements.
I came up with an old .222R Case and a .22 Hornet Case. The later worked out better as it fitted into my Sinclair 30Cal Bullet Comparator Insert and made measurements a little easier and more consistant.
The first step I did was using my Wilson Case Trimmer to square the Case Neck plus reverse in the Trimmer and square the Case Base so that both surfaces are now parallel to each other. There are probably other ways to achieve the same result and if you don't have anything or are unable to do this step then I would suggest you mark the case so that you are taking measurements from the same position each time.
Trim Case Neck ....
Trim Case Base (Head) .....
The neck now trimmed ....
The base now trimmed first the .222R case...

The .22 Hornet Base trimmed and sitting in the Sinclair 30Cal Bullet Comparator Insert....
The assembly mounted into the Comparator Body and Anvil attached to Digital Calipres with .22 Rimfire ready to measure.
Zero Calipres on the cartridge case....
Insert your ammo, take measurement and sort in either 0.001" lots or even better.
The same proceedure without a Bullet Comparator to use. Just try and be consistant with the position of the measuring case and how it sits between the jaws of your calipres.....
I use ammo made by Lapua, SK Rifle Match and found that this was the most consistant with headspace measurements, I had about 25 out of three boxes (150) I sorted that were outside the main dimension. The other ammo I had handy was two boxes (100) of SK Standard Plus and out of those I ended up with three main rim thickness sortings. Even though both types of these have the same specifications like velocity I have the feeling that the SK Rifle Match might already have been rough sorted in the factory.
I have done this to all sorts of rimfire ammunition and achieved the same results, more consistancy and much better accuracy. Even with the likes of .17HMR it was the same.
Would have shown some targets but during this week it has been blowing a gale with up to 50km winds so I'm not going to attempt a demo with sub velocity ammo under these conditions. Test targets and photos to follow in time.
Hope this helps someone.
There is a pretty easy way to improve both and that is to sort your ammo by Rim Thickness in various grades of thickness of the rim. A Rimfire is Headspaced on it's rim and as the thickness here can vary somewhat it affects overall accuracy when the cartridge sits in the chamber at different depths and / or position from the Bolt Face. Keeping this constant through a number of rounds helps a lot with accuracy and reducing that crazy wild flier that seems to creep into any group.
Target shooters do this measurement but it will help with any form of shooting a Rimfire even hunting to know you can be more consistant with your point of impact.
There are various Gauges you can buy to achieve this measurement and costing upwards of $70.00 or more but one can be made fairly easily from a fired .22 calibre centrefire cartridge. My method is just one and depends on the equipment you have at hand but start by finding a fired .22 calibre case that your Rimfire Ammo will slide down the neck of easily. Do not size the case but remove the spent primer so it doesn't interfere with your measurements.
I came up with an old .222R Case and a .22 Hornet Case. The later worked out better as it fitted into my Sinclair 30Cal Bullet Comparator Insert and made measurements a little easier and more consistant.
The first step I did was using my Wilson Case Trimmer to square the Case Neck plus reverse in the Trimmer and square the Case Base so that both surfaces are now parallel to each other. There are probably other ways to achieve the same result and if you don't have anything or are unable to do this step then I would suggest you mark the case so that you are taking measurements from the same position each time.
Trim Case Neck ....

Trim Case Base (Head) .....

The neck now trimmed ....

The base now trimmed first the .222R case...

The .22 Hornet Base trimmed and sitting in the Sinclair 30Cal Bullet Comparator Insert....



The assembly mounted into the Comparator Body and Anvil attached to Digital Calipres with .22 Rimfire ready to measure.

Zero Calipres on the cartridge case....

Insert your ammo, take measurement and sort in either 0.001" lots or even better.

The same proceedure without a Bullet Comparator to use. Just try and be consistant with the position of the measuring case and how it sits between the jaws of your calipres.....



I use ammo made by Lapua, SK Rifle Match and found that this was the most consistant with headspace measurements, I had about 25 out of three boxes (150) I sorted that were outside the main dimension. The other ammo I had handy was two boxes (100) of SK Standard Plus and out of those I ended up with three main rim thickness sortings. Even though both types of these have the same specifications like velocity I have the feeling that the SK Rifle Match might already have been rough sorted in the factory.

I have done this to all sorts of rimfire ammunition and achieved the same results, more consistancy and much better accuracy. Even with the likes of .17HMR it was the same.
Would have shown some targets but during this week it has been blowing a gale with up to 50km winds so I'm not going to attempt a demo with sub velocity ammo under these conditions. Test targets and photos to follow in time.
Hope this helps someone.
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