Fireforming the 257 AI

[ShadeTree]

Tried 5 the other day, wasn't happy with the results. Accuracy was fine, shoulders formed out good. But I was getting a distinct stretch ring well ahead of the web. Looked like about where the heavy taper might start on a factory chamber/case. 3 were worse than the other 2, but all of them bad enough I wouldn't want to re-use them.




The only thing I could come up with was that I had my die set up for the false shoulder so that I was just getting snug right on final closing, and that strong mauser mainspring was driving the case right past that and I was back to square one as far as headspace.

Loaded up 5 more with my die turned up some so that I was getting a crush fit on closing. Chambered each one after sizing to set the false shoulder, then loaded them.

Bingo. Got 5 cases with no visible stretching even when looking closely at the same area with a magnified jewelers loop.




Didn't shoot as well as the firefomed cases using a much higher charge of 4350, vs this H4895 load, but doesn't do bad. 4 shot group was under 3/4", 5 shot was 1.040". Speed was way down comparatively, but will still work as a hunting load for that bullet.

 

[ShadeTree]

Oh and to add something else to the mix. 14 of these factory cases wont let me begin to close the bolt just as they are with no false shoulder. Measure as much as .008 longer to the shoulder than the others that I had to form a false shoulder for because they are short.

So is my chamber off on headspace some? Who knows with that kind of variance. With another type of factory brass it might be a perfect crush fit. Or with factory loaded ammo.

Boggles my mind at some of the lack of QC on factory bulk brass. I hate to say it, but I've seen way more problems with American brass than others. Now factory loaded ammo, doesn't appear to be so.

 

[Seabee]

I lost 1 case to a separation when forming 257ai. I wet a patch with a light amount of oil and used a moderate load and all formed fine. The lubed chamber helps keep the case from gripping and holding the chamber wall. I normally never have lube in the chamber.
Perhaps a larger false shoulder would help. Interestingly enough, my rifle is a Mauser 98.

 

[SJB358]

Looking good. Seems like you’re getting it nailed down real nicely. Those cases look pretty danged neat.

 

[ShadeTree]

I lost 1 case to a separation when forming 257ai. I wet a patch with a light amount of oil and used a moderate load and all formed fine. The lubed chamber helps keep the case from gripping and holding the chamber wall. I normally never have lube in the chamber.
Perhaps a larger false shoulder would help. Interestingly enough, my rifle is a Mauser 98.

Sorry late responding. I thought about lubing the cases after I got a stretch ring on the first 5 cases, but was reluctant to put all that bolt thrust on the old girl if I didn't have to. Decided to instead set the false shoulder so that it was a crush fit on closing, and that fixed the issue on the next 5 that I tested, so as long as it keeps working I'll probably stick with that method for fireforming in this particular rifle.

 

[ShadeTree]

Looking good. Seems like you’re getting it nailed down real nicely. Those cases look pretty danged neat.

Thanks Scotty. I don't necessarily like the fact that I have to burn up primers right now to form cases, but yeah they're pretty sharp looking formed out. At least I have plenty of primers from some old reloads I picked up to use for such things.

 

[BruceP]

Let qualify (or maybe disqualify) my comment by saying that I have never formed 257AI but when forming 257 JDJ which not only sharpens the shoulder but blows it forward I use a 120 grain bullet and jam it heavily into the lands to help hold the case head against the contender frame to help cut down on stretch. So far it has worked fine.