Any suggestions for why this case failed?

Bushmaster

Elvis...It is entirely possible that the sports shop set the shoulder back too far also...

gelandangan

You can fix headspace issue in a rolling block by ring lining the face of the chamber or a shim on the breech.

A good gunsmith should be able to silver solder a shim onto the face of the chamber or breech.
Mind you, there is a lot of butchers out there posing as gunsmiths that may
damage your chamber or breech by overheating it while silver soldering thus render the gun unsafe to fire.

slimjim

Keep the ideas coming!

When I get the broken brass out, I still don't think I'll use the Winchester brass. Looks like my only other choices are Starline and Remington. I need to avoid nickle plated. Starline is so much more inexpensive than Remington, I'm aprehensive about using it.

fnuser

crush a lead pellet between the block and the rim depression of the chamber it should be close to .070" the (headspace of a 45-70) if it is much bigger then you have excessive head space, another cure instead of shimming is setting the barrel back. if its not say under .072" then it was probably just a bad case.

slimjim

I checked the four cases I shot before this one. I don't know the order I shot them in but the primers are proud (moved out of the pocket) the following amount: .004, .010, .012, .015. Makes me think the cases were progressively sticking to the sides of the chamber more and more until the case fractured instead of the primer moving (its flush on the broken case).

Bushmaster

Make sure you know and understand the progression of combustion in the case and chamber...

1. Firing pin strikes the primer and shoves the case forward in the chamber.
2. Combustion takes place pushing the primer out the amount of the head
space. Case expands and grips the chamber.
3. As the pressure starts to drop the case is slammed back against the
breach face reseating the primer.

If the head space is excessive the case can seperate (as your photo shows) between #'s 2 & 3...

Pumpkinslinger

I think Fnuser has an excellent idea! The headspacing is about the only thing I can think of that would cause a case to separate like that. I've got a repro rolling block (Pedersoli) and I'll try Fnuser's method if I get a chance soon just to see what I get.

Elvis

yes bushy you could be correct. I only partial resize and have no issues.the idea of putting a no go gauge in and trying to force the bolt shut to see if chamber is correct size didnt impress me much either.hopefully this case is just a bad case [pun intended]

slimjim

I don't have any lead around but I did put just a short case head in an used a feeler gauage. Case rim was .063. At first I was getting some close tolerance with only .007 fitting. Then I started to look for ways to ensure I had all the slack taken up. When I dropped the hammer, the case went in further. Now I get a .014 in behind the case base and I can jam in .018.

I had a RB Gunsmith check it out. He said it was a bit loose but should shoot ok if I indexed the brass. Maybe this gab is too much or Aloysius' idea of the o-ring will work well enough.

slimjim

Pumpkinslinger wrote:

I've got a repro rolling block (Pedersoli) and I'll try Fnuser's method if I get a chance soon just to see what I get.

I've seen the new Pedersoli rifles and they are much tigher than mine. Interested in what you measured.

1895ss

Aloysius wrote:

Slimjim, on the South Africa forum they give advice for the Lee Enfield to put a small O-ring on the rim before you use that brass for the first time. This way you push the cartridge to the bolt.
And afterwards you just necksize and don't need the O-ring anymore.

The minute I did understand why and how, I also understood I'm still not too old to learn.
What works on a .303 British could also be helpfull for a .45 Government?

The 45-70 is not a bottle neck case, it is a straight wall case there is no shoulder, it head spaces on the rim. Bushy's idea of a brass drift may be better then a wooden drift and I would sure try one or the other or both.

slimjim, I would bet if you switch to Remington brass you may get rid of your problem, cause it will handle more pressure then the WW brass and it is much better quality and or you may have to fix that headspace problem.

PaulS

Brass is supposed to be elastic enough to expand to the case diameter and then spring back about .0005 to 0015" releasing its hold on the chamber.
If the remains of the case is still that tight to the wall of the chamber then the brass had pressure on it that exceeded its elastic limit.
To me, that means over pressure - whether you were at the highest listed load or not. I have run into this with my 357 Maximum - and had no more problems after reducing the load 5%.

1895ss

PaulS wrote:

Brass is supposed to be elastic enough to expand to the case diameter and then spring back about .0005 to 0015" releasing its hold on the chamber.
If the remains of the case is still that tight to the wall of the chamber then the brass had pressure on it that exceeded its elastic limit.
To me, that means over pressure - whether you were at the highest listed load or not. I have run into this with my 357 Maximum - and had no more problems after reducing the load 5%.

I agree ......... but we are talking here about Winchester brass in a 45-70.................. If you don't start the bullet perfectly straight, when seating bullets, you end up with a bulge in the side of the case, this doesn't happen with Remington brass because it is a bit thicker and much stronger. 45-70 WW brass is very soft it seems.

fnuser

14 + 63 = 77 that could be out of spec.

Bushmaster

That's my view too fnuser. It looks like the case is seperating at the point where the case is starting to get thicker. The thinner part expanding against the chamber and the thicker part blowing back against the breech face. Hence, seperation...