Internal ballistics frustration.

meichele · #1 12-21-2006, 02:10 PM

To all,

I have given up trying to figure out this problem. Any ideas might help.

Problem:

When I use unfired brass and fire them 1 time with my top loads, which are not that hot, they extract perfectly. After I resize and reload the same cases (I full length resize them back to exactly what they are when new) and fire them again with the same load (bullet, powder, powder charge ect...) the extarction is somewhat difficult. The 3rd time they have to be tapped out with a cleaning rod after it pulls the sako style extractor apart from the bolt. Thank God I can reinstall it.

Any ideas??? Anybody else experianced this?

Rifle is a custom 300 RUM on a 700 action. Chamber is a tight neck .333 neck diameter. Brass is turned so that the loaded round 's neck is .331 and some are .330 Either one makes for the same problem.

Is it that the round just generates that much pressure that cases are only good for a couple shots or am I missing something?

I am also using Nosler brass. Remington brass isnt any better, in fact I can only get 1 firing out of them. The starnge thing is, it has only started doing this between the 400 and 500 round count.

Thanks for any thoughts.

Mikecr · #2 12-21-2006, 03:19 PM

Couple things I wonder:
Do the offending cases rechamber without resizing?
If they do, how difficult is bolt closing/turning?
Do the cases tap out easily with a rod?
Has the brass been annealed below the the necks?
Has this extractor been worked on, or even disassembled by anyone?

meichele · #3 12-21-2006, 04:01 PM

The offending cases meaning the ones that have to be tapped out. No they dont rechamber easily. VERY difficult. The new once fired brass chambers flawlessly. They do not come out easily with a rod but I dont have to hammer them out either. Brass has never been annealed at all and the extractor was installed by my local rifle smith who built the rifle. It is a sako style extractor, I forget the brand name of the components used.

älg · #4 12-21-2006, 04:45 PM

Are you turning the necks every time you resize?

meichele · #5 12-21-2006, 05:29 PM

I run them through the tuner, yes. After I full case size them I do it to ensure any brass that worked its way forward gets eliminated. Typically, after the first firing and resizing, I only need to do it during the second loading. I still do it after that though.

Buffalobob · #6 12-21-2006, 05:54 PM

Have you checked to see if the case bases are still square after the first firing?

meichele · #7 12-21-2006, 06:49 PM

Not sure how to officially check that, but they appear to be OK.

I may have figured out at least part of this problem. Tell me what your opinions are of this.

New case from base to shoulder (using a comparator) is 3.990" Fired cases are 3.993" I had been bumping the shoulder back to 3.988" Do you think that has anything to do with this? Should I be setting the shoulder back any at all or less than I have been? I have already reset my die to bump it back only 0.001". Will see if that helps any.