Lapping action

[RustyRick]

I have only been neck sizing as my logic says that a fired case is "form fitted". I haven't minded a little tightness upon bolt closing (when I know my seating depth) because my logic says it's not going to stretch much if any upon firing. It's can't exceed the size of the chamber at anytime during firing. I'm currently running 6 - 7 rounds without any case being thrown away. ??? But maybe I'm out to lunch and missing something.

 

[J E Custom]

I have only been neck sizing as my logic says that a fired case is "form fitted". I haven't minded a little tightness upon bolt closing (when I know my seating depth) because my logic says it's not going to stretch much if any upon firing. It's can't exceed the size of the chamber at anytime during firing. I'm currently running 6 - 7 rounds without any case being thrown away. ??? But maybe I'm out to lunch and missing something.

You are not out to lunch by any means. Neck sizing only, prevents the brass from being over worked and adds life to it. It does however get harder and harder to extract if it is not partially
sized occasionally.

The chamber does expand during firing, all though not very much, but it does not exceed it's yield strength so it returns to its original size after firing. The brass however does expands with the chamber, but it reaches it's yield strength and wants to remain the size of the chamber when it reached maximum pressure,causing it to be tight and difficult to extract.

This is the reason that over pressure loads are even harder to extract.

This is also the reason that larger barrel diameters and longer shanks are desirable for large diameter cartridges.

The more brass is fired, the less malleable it becomes and the less it will be crushed by the chamber
making it harder to eject.

J E CUSTOM

 

[acloco]

I machined a stub that threads into the action. Center of my "stub" is drilled so that I can insert a spring and a single ball bearing. Ball bearing centers on the firing pin hole of the bolthead, which should aid in centering the boltface with the action threads.

Keep turning the stub in to the action to increase spring pressure while lapping.

 

[hemiford]

Acloco,
This sounds very interesting, what you are doing, but I can't quite
visualize/grasp it. You are pushing a ball bearing through the (chambered)
cartridge neck ?

 

[trigger103]

what compound would you recommend for lapping lugs? is there a certain grit.

 

[IdahoCTD]

He is lapping with the barrel off of the action. I have a similar set up to lap lugs. I use aluminum oxide paste as it is non embedding. I don't remember the grit off hand but it seems to me I use either 240 or 400grit. You can buy it from Brownell's.

 

[trigger103]

ok thanks