Formed 7x57 Rem brass to .257 Rbts using Rbts sizing die. Loaded 117-grain SST and 44 grains H4831 SC. 37 of 100 cases cracked at shoulder-neck junction. Is there a better fire-forming load?

Not complaining, just learning. (Something to do Atkinson.)

You don't say what brass you used, but I have had much better luck reforming new brass. If it is not new brass, I would recommend annealing the neck and shoulder to soften the brass and reduce the work-hardening. Good luck.

Well, he did say Rem. brass but I agree with you that neck + shoulder annealing is the route to go. I have found over the years that I have more case longevity using W.W. brass. Just my opinion + experience.

Brand new Remington brass. Never annealed anything before -- guess I could add that to the repertoire. Hornady brass from factory loads is available, just thought I'd venture out with the 7x57 approach. Thanx!

Lately 7x57 brass seems to be about as hard to come by as .257 Roberts. I recently ordered some Prvi from Powder Valley. It appears that Lapua no longer makes 7x57 or else it never makes it to the states.

In this time of panic/crisis, it seems most items in the ammunition world are hard to come by. If you are new to case annealing you might consider going to your local welding supply store + buying some of the heat temperature marking pens.

I have had no trouble with Rem. brass, but I used new stuff..Fireforming shouldn't be that complicated. I do a lot of it with my 8mm/06 Ackley and with some Rem and WW brass and PPU also..My question is did you seat the bullets out to engage the rifling? what was your fireforming load? How many times had your brass been fired, some of this might help you out??

If brass was fired in the 7x57 more than one time then annealing is the answer, and not a bad idea at all between every firing if your set up to do it..most are not.

Sometimes its just best to start with new brass in the caliber you have, and skip the fireforming route, figure the cost..

New brass. Full load. Not seated to engage rifling. The cost was 1/3 of 66 bucks. still haven't read what a good fire forming load would be if I were to seat to rifling, etc. Medium load would be 40 grains H 4831 SC with 117-grain bullets.

What you describe is quite unusual. I've made upteen .257's from 7x57 (and even from .30-06); .243 from .308; .25-06 from .30-06; 6.5 Remington Magnum from .264 Win; .300 Blackout from .223; .256 Win from .357 Mag; ad infinitum. Never have any cracked at the neck/shoulder joint. I have to think that the batch of brass you happened to use was brittle in that area, although new factory brass is usually pretty ductile and properly annealed. I'd write it off to bad luck and try another batch, preferably of some other brand.

Hint: Don't simply run your .257 FL die all the way down hard against the shell holder (unless necessary). Rather, back it off about .05" and gradually lower it until the case chambers with just a bit of resistance. This will ensure exact headspace and no stretching of the case at the critical web area.

Using a good case lube like Dillons makes the task easy with a minimum of brass loss. Was told that Dillon case lube can be duplicated with lanolin and alcohol mix.

I've necked used 308W brass down to 7mm-08, 243W brass up to 7mm-08, 25-06 brass up to 6.5-06 and 30-06 down to 6.5-06 with out any cracking issues at all and without annealing.
Only size your cases to give a snug fit, a slight resistance when closing the bolt. Annealing won't hurt but surprised you would need it with new or even once or twice fired brass. Maybe your new brass is abnormally hard or wasn't annealed correctly when manufactured so annealing before sizing would fix that.

I've neck resized numerous calibres over the years with good case longevity, all except for the 30 Gibbs, for some reason I got a very short case life with this one.

That was your brass; I have done this before using 7mm and 25-06 brass; never any cracks. And I have formed lots of stuff from other stuff; no cracks; brass is very ductile and malleable; that is why we use it for cartridges.
Fire forming? what are you forming? The die did that. You just had brittle brass; even if new. Should not need it. But you can do it anyway.
Its wasn't the case lube....

Got it.

Use a squib load of slow burning powder and seat the bullet out to touch the lands to fireform.

Just one more factor in approval of neck annealing. You are correct Pegleg to a point. I have found that when not using a slow burner I have used Cream of Wheat cereal or 7- 10 Gs of 700X. That WILL fire a case with no trouble. But in reality, one can work a regular load + use it. It will perform as well as the AI the 1st time. After that, build to your performance ideals. Long way around the barn. Keep it simple. Hunt with your regular rounds + after the fact you have new brass for your chamber; end of story.

quote:

end of story.

If it were only so!

Pegleg,
Aren't there cautions on using very light loads of slow burning powder in cartridges? It is thought to promote the possibility of detonation with dangerous results.

I'm with Randy, use a fast burner like 700X or Red Dot.

WEll my guess is you needed to neck ream the thicker Remington brass, sometimes it forms a donut at the neck juncture, some times necking down makes it even thicker..I suspect this is your problem, not inferior brass, Remington is excellent brass..Neck ream inside would be my advise if the donut is there, you should be able to feel it with a bent paperclip, the outside neck reaming is probably a bit better if you dont detect the donut, maybe, perhaps!!!???? In reloading lots of guess and by gosh works quite well within reason..

Firefromin is best IMO with a fast pistol powder such as unique or even Bullseys with a dose of cornmeal to hold the powder in place and a tab of wax to hold the cornmeal, point up and shoot. Slow powders have been known to cause double explosions and that's bad, bad. This is an accepted "fact", but Ive never had it happen to me..soooo????

I would use 8 to 11 grs. of Unique to fireform, on top of that put some kleenex then cornmeal and wax the top to hold the load..I have a spread of wax on a piece of glass thats about 1/4 inch thick or less, no bullets used..

I have in the past shot factory 257 in a 7x57 and never lost a case, same with shooting 30-06 in a 338/06 or 35 Whelen...Some worry about a wobbly 30 cal down a 35 cal hole, but steel is harder than copper or lead soooo. at any rate it works and was a common practice back in the day of the sho nuff wildcatters...

You should not lose a case fireforming but its not uncommon to lose one now and then, guess its brass thats faulty and just happens..

I used 6mm Remington brass to resize to 257 Roberts. It was very easy to do. Quit when I got more 257 Roberts cases.