Case Separation - What are the causes?

[FatJackDurham]

I got my Remington Rolling Block No. 1 today. It's definitely a project gun. Taking it out to the range, I found that It had the tendency to cause the cases to separate on the heavier bullet. It's been relined and rechambered for 45-70. I think it was an Arab country gun because there is a stamp of a crescent and star on one of the barrel bands.

I had loaded a 500 grain bullet with 70 grains of 777FFF and a 430 Grain with 65 grains of 777FFF. The 430 seats about an eighth of an inch deeper, so I used a little less power.

The 500 grains all ended up separating the cases, though the exact load fired in my springfield with no ill effects. The 430s didn't separate, but I did notice a stress ring forming on the case in the same location as the break in the other case.

I noticed that the breach can move back just a little, even with the hammer forward, and I wondered if this is causing the rear of the cartridge to move back wards and tear, or if it's something else.

Any rolling block experts? Also, the brass was R-P and has only been used 3 times max.

[awp101]

Probably ex-Egyptian. I don't have my books handy but IIRC it would have been .43 Egyptian initially.

You probably have one of two things going on, maybe both. Out of round chamber or extra headspace. I know there's ways to fix those problems, I just don't have much information on how to do it so I'll leave that to the RKIs. The only thing I can think of if the headspace is bad might be to take a chamber cast, determine the OAL and load the rounds a little longer.

[Hayseed]

Headspace should be .002-.003" if I remember right.

[Chuck 100 yd]

In that rifle, I would load the bullets out to the point it would take a little thumb pressure to seat them so the breech block will close all the way and don`t crimp at all.
If the bullet bumps up before leaving the case, it will try to drag the case along with it, stretching the brass even with proper head space. This also can happen in BP bottleneck rounds causing the neck to be ripped off of the case.

[FatJackDurham]

Chuck,

I was worried about that, but I thought with a BP load that would not necessarily be a problem.

The barrel looks like it wasn't seated all the way when they reattached it. The center mark is .060 off. If this is a BP barrel with a .975 shank and a 12 TPI pitch, then that ciphers out to .0033 added to the head space, which might account for the breech being a little loose when closed. I am waiting to hear back from a gunsmith who might be able to tighten it properly.

I did crimp the bullets, as well as doing a full length resize. THe neck sizer die I think is .457, so the bullets I used, being .459 are probably too tight in there anyway.

However, what I find strange is that I know the chamber in my Springfield is loose, especially compared to this Remington, but I have had no issues with this. That breech, I think, is good spacing. I think headspace is the issue, and I will work with a gunsmith to get it corrected.

[FatJackDurham]

Another thing I just noticed was that the primers are extruded on some of the case I fired. that is a sign of excessive headspace too, right?

[Buck Elliott]

Extruded primers would be a sign of high pressure, or more likely, an oversized and sloppy firing pin hole in the breech-block..

Breech-block movement with the chamber empty is relatively unimportant.. What might matter is the amount of movement when the rifle is loaded with a live cartridge..

[Hayseed]

Put a sized , unprimed case in chamber , close block and let hammer down. Now bring block back against hammer where it rides under breech block, start slipping feeler guage between case rim and breech face.Largest feeler is headspace you have .

[shooter]

Did you happen to have those stored in a plastic cartridge box? If so, I think Griff can give you some insight on your problem.

[Griff]

Did you happen to have those stored in a plastic cartridge box? If so, I think Griff can give you some insight on your problem.

Yes. Don't store empty brass in a plastic box like the MTM. I had a case separation on a round a few weeks ago. Loads were "hot", near max, but still about a factory equivalent. The separation ocurred at about the point at which an empty case would rub against the plastic case as they rattled around. So ALL empty brass is now regulated to a bag or bucket.

[FatJackDurham]

!

What is the thinking?

[John Y Cannuck]

Looking at the pics, I doubt you have a pressure issue. Most likely it's headspace. Extruded primers, that is primers that are pushed out of the back of the case, (not flattened) won't happen unless there is room there for it to happen. Again, headspace .

In a straight walled case like the 45-70, I think the suggestion that you seat the bullets out to contact the lands has merrit, for BP pressures anyway. That way it will hold the case against the bolt face and limit stretch.
If that works, you've identified the issue.

It's possible that it has worked loose. If it has sights, look to see if they are on center above the bore. May just need to be tightened.
If the barrel is clean of dovetails, it may just need to be tightened

Other than that, it means getting it fixed.

If it has dovetails in the barrel, and they are on center above the bore, the barrel will need to be cut back and tightened by someone who knows what they are doing to get the dovetails lined up again unless it's a full turn out.

Can you return it and get it corrected?

[FatJackDurham]

John,

Thanks. It might have just worked loose. It came off a little easier than i think a rifle barrel should!

No dovetails.

I considered returning it, but, my inner mad scientist has taken over and now i must tinker with it!