45-70 brass shorter after fire forming

bandanaman

bandanaman

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Here is my " Dilema ".I have taken new Starline brass,sized to 2.1[very , very little trimming reqd],bevelled throat,uniformed primer pockets,deburred flash hole , loaded,fire formed,and now the brass is at least up to .010 shorter.I've checked them enough to know it has gone in the opposite direction to what I was expecting.Now the brass measures 2.090 +/- .What am I missing here ???? I half expect to be embarrassed but I haven't come across this yet in my reading.I am shooting an 1874 model reproduction Sharps.Should I have fire formed them before sizing ??? With what I trimmed I think I would still be coming up short!!Being a single shot I don't expect any issues as I don't expect to be a match shooter but I was trying to follow the procedures to the letter.This is another new game to me.
 
Try resizing it and measure it again. When brass is blown out to chamber dimensions it often shortens.

As for being 2.090", that's a non-issue. Even if you've determined the best possible load and it needs to be crimped in a crimp groove, 10 thou will not make any difference.
 
Thats pretty normal unless you have a really tight chamber. I never trim until the brass is at fired at least twice. Most .45-70 chambers are long anyway so you'll almost never need to trim.

Now that you have short brass, you might find it works best to leave a lube groove exposed right at the case mouth. That will help reduce leading. I wouldn't crimp those.

Chris.
 
The thing you have to remember with the 45-70 case is that they headspace on the rim, not the case mouth as a rimless cartridge will. A shorter case (even much shorter cases than your will make no difference), equate it with using .38 sp in a .357 mag, a full 100 thou shorter but works with no danger at all.

If they get long enough that they become difficult to chamber then I would trim otherwise load up and shoot'em.
 
Yep, the metal to make it grow outwards has to come from somewhere. I would have expected that it would come from stretching the wall thickness. But clearly it also converts some of the length into an increase in girth. So I've learned something as well.

Crimping for single shot rifles is really more about just removing the flare to allow the casing to seat. And a fairly common practice is to size the necks such that the bullets are under light enough neck tension that you can leave them a touch long and then force the casing onto the bullet that last .020 to .030 when seating the cartridge. It's called "breech seating" if I remember rightly. I haven't tried it yet. I just seat my .38-55's under a little more neck tension than that and go for an OAL such that I'm about .010 away from the bullet breech seating on the start of the rifling. But it's a technique I want to try sometime soon to see if the lower neck tension along with the breech seating aids my accuracy. With the bullets I'm using leaving them long so they'll breech seat means that a little of the last lube groove will be exposed.

In any event a lowly .010 isn't a deal breaker either way. It just means that a little more of your bullet will be exposed. Even on a lever rife I doubt that .010 would matter either.
 
Ya, take a cylinder and push the sides outwards (The brass case expanding out to the chamber) it's going to contract in length right?
 
So. you trimmed first, eh? :)

Next time around, measure them, and if they are not too far out of spec, leave them alone until the first firing cycle sizes them to your chamber. Probably woud not hurt you to have some idea what the actual dimensions of YOUR chamber are, too, so you will know if there is actually any need to worry about the cases being over length.

But, as the others are saying, it's really not a big deal coming up a bit short. Seat the bullets out a bit further, add a bit of powder to get the same compression, if using black powder, otherwise, live and learn.

There was a guy that was working on a brass stretcher, which sounds like a joke but isn't. He was posting on the ASSRA forum and it was a draw type die that lengthened the cases for when you could not get brass that was quite long enough. Straight wall cases only. Hydraulic. Expensive. Such was the thinking in his particular world (BPCR, IIRC).

Cheers
Trev
 
Trev, I bought one of those ( Kal-Max ) stretchers. I've never used it :). Interestingly it's made in Canada. I also bought one of the $40 stretchers from Buffalo Arms to play wih. It just uses your reloading press. It works well but thins the case mouth more than I'd like. I've never used it except to see how i works.

I like my brass to be as long as the chamber if possible. The easiest and best way IMHO, if you have a long chamber, is to buy longer brass and trim i down. In this case .45-90. Interestingly, most of the .45-70 chambers I've measured are too long ( C. Sharps and Browning BPCR especially ), probably for liability when guys shoot hotrod smokeless loads out of them. The Shiloh chambers seem to be a lot closer to spec.

Seating the bullet out with a lube groove at the case mouth seems to work well too with short brass. No so much for paper patching :)

Chris.
 
My Shiloh chamber measures 2.111, and my Remington brass after fire forming is mostly 2.088, with a few at 2.092 at the longest, so I don't trim at all.
I have experimented with stretching brass with the $40.00 tool, and it does work well, but I found with brass at near maximum length, the cases would stretch, requiring trimming.
With the shorter brass, I don't get any stretching at all. I don't resize my brass either, so it doesn't get worked much.
 
Thankyou Gents ,in retrospect it all makes sense now . All my previous reloading has been bottleneck cases where trimming was eventually reqd or when making wildcat calibers.The next lot of brass I try will get fire formed au natural and then I will go from there.With this rifle I intend only to neck resize the first half inch at most and expand for tension .I haven't had any chambering issues to date .Lots more to read up on and experiment with to have something ready for fall to try and make some meat with this smoke pole.
 
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