TargetTalk

hello
can someone explane wy a perticular rim thickness works great with my rifle and a other rim thickes that is 0.02 mm different causes the groeps to become larger.
this i have tested with lapua superclub a cheap but great practice ammo.
And is the richt rim thickness the same for more expansive competition ammo witch i have not tested yet because off the price. Im stil a student so don't have mutch money.

like to hear something
Stefan

Many .22 rifle shooters have found rim thickness to be a factor in group size. It affects consistency of ignition.

Eley is pretty consistent from lot to lot, so if your rifle likes that rim thickness, you're in luck!

Richard Ashmore

so why does It affect consistency of ignition?
is it because the space inside the rim that is filled with the ignition powder. is different in shape from the variation in thickness and there fore when hit by the firing pin a differtent burning speed is the effect.
Or the different lengt that the firing pin has to travel before igniting the .22

And is it the same rim thickness that works well with al the different types off competition ammo from the same manufactore?

And does it differe between other lots from the same ammo?

i hope someone can explane all of this

Stefan

The different rim thicknesses affects the headpace in the action, which is critical to accuracy.

I sort all my ammo by rim thickness, I use a Gehmann Rim Thickness Gauge

I've done various tests on my rifle and rim thickness was one test that I found to be very important.

Ryan
Intershoot

SP van de Graaf wrote:
And is it the same rim thickness that works well with all the different types off competition ammo from the same manufacture?

And does it differ between other lots from the same ammo?

i hope someone can explain all of this

Stefan

I'm sure I can't explain all of it.

The gap between the end of your bolt and the end of the barrel is where the rim resides. The closer to being full that space is, the better. [Compressing the rim is not good.] When the striker hit the firing pin, the energy is used to mash the rim and ignite the primer. The more space there is, the more of the firing pins energy is spent pushing the cartridge into the chamber and less is available for ignition.

Good ammunition has consistent rim thickness. IIRC, Eley is 0.039" with a small standard deviation.

Try looking in the rimfire forums at www.benchrest.com. I have not looked there in a while but remember the subject being discussed.

Roger VA
Micanopy Beach Florida