Fire-forming oddity

[RonnieMilsurp]

Hi there. I'm in the process of forming some .348 Win cases for .50-70. I'm working with 10 cases as a test run. First off, I think I got a bit too eager because I forgot to anneal them. But, other than that, my process was the same as I did with my Swiss Vetterli with Lebel cases: a few grains of pistol powder and the rest full of corn meal, capped with wax, and fired upward to keep the powder by the primer. I did not trim any length off of them before fire forming. This worked fine in my Vetterli.

Every single case came out asymmetrical. That is, on the side that faced downward in the chamber, the wall of the case blew out straight/correct. But on the opposite side, the .75" or so of wall that's towards the rim didn't blow out all the way, but as you get closer to the mouth, it does. I know that the chamber itself is symmetrical because I cast it with Cerrosafe.

The only thing I can come up with is that the block is allowing for uneven head clearance, so the case gets tilted when fired. Though that doesn't explain why the mouth (last half inch or so) of the case seems to blow out more normally. I was able to run them through a full length sizer afterwards, but obviously it can't push the walls out. I even took one and repeated the fire-forming process but turned the case 180 degrees, only to have it come out looking just as it went in.

I'm sure there's something I'm missing here but can't think of what it is. My "screw it" mindset almost let me do a nearly full load of BP with a real boolit just to force it to form the rest of the way, but thought that I'd better ask here first.

[Gewehr-Guy]

You might try the O-ring trick, slide an o ring against the rim so when the breach block is closed, the rim is tight against it. I think the mouth expands better just because it is much thinner than the shoulder portion. Can you find the proper 50-70 brass, they should be cheaper than .348 ? Once a case expands unevenly, it usually keeps expanding on the thin side.

[bertus534]

I cut my 348 cartridges to size with a trimmer anealed them,can be done with temprilac available from brownells or dip them in your lead pot,after that I gently flared the case mouth and anealed again .load the cases and Bob is your uncle. Hope this helpt Oscar



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[BK7saum]

Did you actually fire them with muzzle pointed straight up? i fire formed some 7.62x39 to 401 wsl and they fireformed best with muzzle up. With barrel horizontal, i got uneven fireforming like you are seeing. I would not have thought it would make a difference. I would likely try a little more powder to bump the pressure.

[RonnieMilsurp]

BK7saum, well...not perfectly vertical. I had to get it out past the roof over the benches at the range. Will try more powder.

Bertus: I didn't trim first because I didn't want to over trim them. Made that mistake with my Vetterli.

Gewehr: I may try the o-ring. And no, this .348 brass was significantly cheaper than any .50-70 I've seen.

[bertus534]

I made a chambercast first so I knew
to what length to trim

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[Bad Ass Wallace]

Been fireforming 348 for a long time, use expanders, 375, 410, 458, 510 in gentle steps.

[indian joe]

Been fireforming 348 for a long time, use expanders, 375, 410, 458, 510 in gentle steps.

+ 1 to Wallace - gentle steps

50 alaskan brass was available about a year ago, that would be much easier if you can find it

I formed 348 to 45/75 - blew em out using full case blackpowder and a proper lead boolit - accuracy was quite acceptable and the trigger time did me good

be aware 348 winchester cases are way under (10 to 12 thou) SAAMI spec so you end up with a goofy lookin coke bottle deal at the back end so if you can accomodate the "O" ring idea I would do it .

[RonnieMilsurp]

What do you mean by coke bottle thing?

Question for all: should I just abandon these 10 cases or will they be ok to fire with a full load?

[uscra112]

You might try the O-ring trick, slide an o ring against the rim so when the breach block is closed, the rim is tight against it. I think the mouth expands better just because it is much thinner than the shoulder portion. Can you find the proper 50-70 brass, they should be cheaper than .348 ? Once a case expands unevenly, it usually keeps expanding on the thin side.

O-ring or a few 1/4" wide wraps of packing tape just next to the rim to keep the base centered. S.O.P. here.

Yes, those cases are spoiled, IMO.

[TD1886]

If you feel it's not locking up even go ahead and use the O ring trick. Other they that I would say if you have enough pressure with the light load sligthly oil your whole case. You'll be surprised even without annealing.

[RonnieMilsurp]

Oil it with... gun oil? Motor oil? Gear oil? What's the theory there?

[uscra112]

Oiling will let the shoulder of a rimless case that's too far back be pushed forward again. I kinda doubt it would help with the O.P.'s problem.

[TD1886]

Oil it with... gun oil? Motor oil? Gear oil? What's the theory there?

Any light oil like gun oil or even Imperial sizing wax.

[TD1886]

Oiling will let the shoulder of a rimless case that's too far back be pushed forward again. I kinda doubt it would help with the O.P.'s problem.

I've done it, it helps out with the web area of the case to fill out evening. This is one way for form a 350 Legend from 5.56 cases, which is kind of dumb to start, but it works. My friend told me of it and I tried it and was a perfect fire form. That tape trick is what I use to get 30-06 to work in the 6.5x55 Swede. 1/8th inch strip right around the solid web part. Bitch to load into the chamber, but the 06 cases comes out perfect.

[indian joe]

What do you mean by coke bottle thing?

348 cases are .542or so at the base - 45/75 chamber spec is .554-6
348 cases are tough brass so it took me several fullcase blackpowder loads to get them blown out right down to the solid head - happily my chamber neck is neat enough that loaded rounds stay centered (at the rear) in the chamber rather than lie to the bottom --along the way they did exhibit a distinct coke bottle look tapering from halfway along the body back to the unexpanded base - had the neck clearance been (as in most rifles) insufficient to orient the round and all the expansion was to one side they woulda looked kinda fugly

Question for all: should I just abandon these 10 cases or will they be ok to fire with a full load?

dont toss it until its irretrievable - do you have access to a 348 FL size die ? resize and start again might work

[deces]

https://www.whiddengunworks.com/hydraulic-form-die/

[uscra112]

I reckon I can fireform an awful lot of cases for $258.99 worth of powder and primers.

[deces]

I reckon I can fireform an awful lot of cases for $258.99 worth of powder and primers.

[RonnieMilsurp]

dont toss it until its irretrievable - do you have access to a 348 FL size die ? resize and start again might work

I do not. What's the potential problem with just firing it with a charge of BP and a bullet? Is the idea that the case wall is now too thin somewhere and could blow out? If so, what part is supposedly thin? The part that blew out like it should or the part that didn't?

Or something else entirely?