TargetTalk

I am starting as a prone rifleman 50m. I wonder how it affects the rim thickness on the accuracy of the ammo .. You want to know which are more convenient ammunition which measure a rim thickness higher or measuring a thickness lower rim ..[/b]

Babillita,

most competition standard ammunition will have a consistent rim thickness. Other shooters have measured rim thickness in an attempt to sort their ammunition, and gain greater consistency. However this subject does not get discussed very often, and seems to give very little benefit for much tedious work.

It is important that the gap between the case rim and the bolt (called headspace) is minimal. If the headspace is too big, cartridge ignition may be inconsistent. Standard headspace for .22 has been 0.042-0.043in. In recent years some gunsmiths have set headspace to 0.040 or 0.041in to suit Eley ammunition, which has a thin case rim. This can be too tight for RWS and Lapua ammunition, which has a thicker rim; the bolt becomes very stiff.

Eley ammunition has quite a thin rim and shoots well in many rifles. RWS and Lapua ammunuition have thicker rims, and shoot very well in many rifles.