I have a Ruger #1 in 30-06 shooting pretty damn well with breech seated bullets but the shoulder is slowly pushing back. Any ideas?

I noticed it after I was de priming on my Meacham tool
I thought it was crud in the neck but it was actuslly pushing forward in the chamber enough to start to basically crimp the front of the neck. This is after about 250 shots on the same case not a big deal to use Another case every two hundred shots but maybe somebody's figure something out I haven't.

I'd think just the brass overall length might need trimming, is it longer now than the starting length? The shoulder could move forward, but there doesn't seem to be any problem with chambering the brass. Maybe, the pressure isn't loaded as high as regular 30-06, but it might be running higher than traditional black powder cartridges? Just guessing.

edit to add, the description does read a little confusing, but I didn't think the neck would start to crimp if the brass got shorter. I suppose unless there was some possible way that the decapper has changed.
And, sorry if I'm completely missing the picture, is there a thinning ring in front of the web?

    Interesting situation.   Probably the primer explosion is pushing the case gradually deeper into the chamber.  Can't be very much or the primers would stick out to where the fired case wouldn't go into your re-and-de.  Rifle primers or pistol primers?   If you want to stop or minimize it, thereby saving your "lucky case", you could probably expand the case to .32 or so and size it back down to where it just drags a little when you close the breech.  That might fire-form it to its original configuration and may harden the neck/shoulder area of the case to where it would hold its shape.
       Failing that, maybe put a note on your club bulletin board describing the problem, and someone would give you another .30-06 case.

CHRIS
RGChristensen

It is interesting. I'd think the primers would back out a bit or the cases would soot over if the brass can't hold the chamber walls. If every thing seems okay, the case has probably settled on some happy medium and can likely be trimmed to the same neck fit as when it started, even though the case legth would be shorter?

Oil, lube, grease the case, very little, and solve the problem.

A #28 Drill is .140 Diameter. Now I do not know for sure but that seems a little excessive. If it does work you would want to make sure that Brass does not ever get loaded with a standard 30-06 load with real pressure. HTH FITZ OLD TUCK

Was that case from a new, unfired lot?   
If so,I think the low pressure is the culprit. To get a more perfect case fit, go buy a new box of .30-06 in the brand you wish your cases to be. Next trip to the range shoot two of them and use one for your 'case'. Save the other fired one in your kit. The higher pressure will result in a fireformed case that pissy, wimpy and anemic loads may never reach in the strong case. When the time finally comes to replace the old one with the spare, get a replacement from the unfired cartridges' box. This should last a long time and give little chance of streaking jacket metal in the bore.

rgchristensen wrote on Jun 14^th, 2020 at 12:16am:


THIS ^^^ EXACTLY.   Been a known issue for generations.  Use pistol primers.  Open the flash hole up to .100".  (Do not use the modified cases for full loads.)

You can salvage a case by lubing it with case lube and firing a reduced load in it.  The case will slide back and the shoulder will be blown forward.  Done this a number of times when I was fooling around with light loads in the .35 Remington. (Until I learned about the above-mentioned workarounds.) Make sure you get all the lube out of the chamber afterwards.  

Phil