Hard bolt pull?

Guys,

I got my Delta 5 shooting pretty good with the 6.5 CRDM barrel. Today at the range, however I had a bit of an issue on occasion pulling the bolt back. No heavy lift. It would happen about every 3rd or 4th round. I'm running 4th cycle gunwerks brass and I'm bumping .002 to 1.504" on the Sinclair comparator. No signs of pressure on the brass, no cratered primers, etc. Headspace is good. This is a 37.2 grain charge under a 143 ELD-X and I'm .003 off the lands. I'm wondering what gives? I have a theory that maybe the neck turning striations have created more friction in the throat upon expansion but I didn't have any loads that were un-turned to test this theory. Maybe that or dirty bolt raceways or mortises? Any ideas? It didn't seem to do this as a .308. Thanks in advance for any insight.

Everything seems right to me but at 4 times reloaded I would be annealing.
It is possible the necks are not "releasing"from the chamber.
I have had this problem with a 300 RUM and solved it this way. Worth a try.
 
Read the entire thread.

You have used the brass for four firings with Gunwerks brass. You might want to retire the brass for now and try another brand.. Lapua would be my first choice. If you do be sure to start low and work up again as internal volume could be different.


A few posters suggested annealing the brass. Unless I am mistaken annealing is used on the case neck, never on the body so don't know how this would help.

Three or four times fired brass will be work hardened near web preventing it from springing back. It is more prevalent with certain brands of brass or some chamberings. I have noticed that WSM, RCM and RUM brass uses thicker case walls which aggravates this issue.

IMO the diameter of the chamber near the web and the diameter of the sizing die at same location does not have a great enough difference. Either get a small base die or make one. OR polish the rear of chamber to make it slightly larger. Either way will increase the difference in diameters.

Did a quick search and found a RCBS small base die


BUT there is an issue:
" These dies size the body of cases somewhat smaller in diameter and also sets the shoulder back slightly more than a Full-Length Sizer Die to ensure proper functioning in the actions of these rifles. Not recommended for ammunition used in bolt-action rifles."

So you either go to someone like Whidden and request a special die or make one. I have used a carbide tool bit to cut through RCBS's case hardened FL die on my lathe. Some material is removed from the top and bottom creating a custom small base die. It solved the issue with my two 338 RCMs and 300 RUM with brass that was fired more than two times.
 
Everything seems right to me but at 4 times reloaded I would be annealing.
It is possible the necks are not "releasing"from the chamber.
I have had this problem with a 300 RUM and solved it this way. Worth a try.
I annealed my 338 edge brass just the neck and shoulder juncture, with fantastic results! They run thru the F/L die like butter. I did my 6xc with the same results! Sure would be nice if companies offered annealed brass options!
 
I annealed my 338 edge brass just the neck and shoulder juncture, with fantastic results! They run thru the F/L die like butter. I did my 6xc with the same results! Sure would be nice if companies offered annealed brass options!
All new brass has been annealed, more than once in the process of making it. Most companies polish the burn off before shipping it out.
 
For the sake of fired forces...
If a case has been fired several times it can be work hardened...
At any firing the neck being hardened could increase the pressures in the web area due to non uniform release of the bullet from the neck..which could make the web area increase...
So if the necks and shoulders are properly annealed..often enough there shouldn't be any excessive pressures to create web increase......
I hope this is close to what most everyone is getting at here...
Layman's terms.....
 
Well, we took a roundabout way of getting to this point but at the end of the day, lots of good advice here and now I have many things to try to systematically figure this out. Annealing is an example of one of those kinds of things that I've thought about but something that I never really saw myself doing. It may be in my future. Thanks again!
 
This seems plausible because in order to only get a .002 bump, I'm just at shell holder contact with the bottom of the die with maybe a very minor cam-over. But if I follow the RCBS instructions I get a distinct cam-over and end up bumping the darned things .006 or better. Maybe if I bump .004 or so I can find a happy medium? Kinda bummed out cause it's shooting so well.
Look into Redding competition shell holders to control headspace. Ended all case separations in my 308 and 300 Weatherby.
 
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