Problems with neck tension - 7mm Rem Mag

[Arkansas Paul]

Hey guys. We're having some issues with neck tension in a 7-Rem mag.
The dies are new Lee dies and it seems that half the rounds we load are having bullet setback issues. We adjusted the dies per Lee's instructions and you can see on the case that it is full length sizing the brass.

Now we did buy some brass that was supposedly "once fired" so maybe the guy lied and it was worn out brass.

What do you guys think is the most likely culprit?

Bad brass or dies that are not sizing the neck all the way?

Thanks.

 

[[email protected]]

Measure the expander button on the resizing die. The die most likely sizes the neck small enough, but the expander opens it up too much when it exits the brass. A little fine grit sand paper and a drill will fix that in short order. I am assuming that you are using full length sizer dies since you talked about used brass from another source other than you (right). Check to make sure that the bolt will close on each case after you size them.

 

[blarby]

^^^^ probably the best answer !

Whats the ID of the neck before seating a bullet ?


Also, when are the bullets setting back ? Are they all setting back on recoil, or somewhere else ? How do they do on the bench/press test ?

 

[gamestalker]

Take one of the suspect resized pieces of brass and measure the OD, if it measures the same as the brass that has good neck tension, then it is indeed the brass causing the problem, thin necks.

If not, and the brass with poor neck tension measures larger OD, then the problem has something to do with either the die, die adjustment, or you may be short stroking the press.

GS