doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com OT - Primers backing out and black powder

OT, but I know some of you can help Loaded some shells for my Martini Henry .450/.577 with about 90 grains of black powder (2F) and typical 480 grain lead bullet. Put some cotton filler and a wad in the neck to keep the powder from moving. Loaded them in nice jameson brass.

Some of the primers backed out on firing. I can't believe the pressures were too high. Any suggestions?

Also any suggestions on a smokeless load. I read some use IRM 3031. What about trail boss?

Jerry

I would start with checking the head space....its hard to create enough pressure using bp to back out primers.
Steve

.450" MH: a man after my own heart!

It sounds like a little bit of excess headspace (can check on a chambered case with feeler gauges; I don't know what the correct max headspace should be, but I imagine in a 130ish yo military rifle a bit of slop is acceptable) combined with the low pressure of BP. The lower pressure may mean that the case head is not forced back hard against the breechblock, meaning the primer can back out a little into the space. I've seen it, but never regarded it as a problem.

I have used 30gr ADI AR2205 under a 500gr gg bullet. It was accurate, mild on the shoulder, but I'm not sure I liked what may have been happening inside pressure wise - very small charges inside cavernous cases worry me. Trail Boss could be a winner, but I've not kept up with that development. 1f *real* gunpowder works very, very well for me!

Have you consulted the Martini gurus on: http://britishmilitariaforums.yuku.com/

RG

Primers backing out is usually an indication of very LOW pressure.

This will happen, for instance, when shooting primer propelled wax bullets or plastic practice bullets in a revolver.

Normally, recoil sets the cartridge case back against the breech face and irons the primer flat to the case head.

Check the contour of the primer after firing. If it's still round at the edges, the pressure is very low.

It can also be caused by excessive head space.

This sometimes happens with starting loads in the flanged nitro expresses also. It's due to low pressure, not high. The .577/.450 headspaces on the rim like the nitro expresses do, so I doubt headspace has anything to do with it. I think the difference between modern boxer primed cases vs the original Berdan primed with it's much larger cap plays a role in this as well.

Gentlemens:

Backed out primers are caused by a number of factors working in concert. One thing for sure and for certain is if the primers have backed out a noticeable amount, you have excessive headspace.

With a rimmed case like the .577-450, the case rim fits into a recess that, in a perfect world, would be exactly the same depth as the rim thickness. In the real world the depth is always greater by a small amount and as long as the difference is small it is of no consequence. In fact it is necessary.

When the firing pin falls against the primer the whole case is pushed forward as far as it will go, which should be only a few thousandths with properly matched cases and chamber. When the priming compound explodes the primer cup is driven backwards against the breech while the case stays still. The primer now protrudes from the case by whatever amount the rim recess is greater than the rim thickness.

When the powder charge subsequently explodes (this all happens so fast it seems to be all at once, but is indeed in sequence) the pressure pushes the case back against the breech, reseating the primer. The case goes backwards and the bullet goes forward and all is right with the world. When you remove the case the primer is where is was when you put the cartridge in the chamber.

With a low pressure load it sometimes happens that, when the main charge explodes, the case expands and grips the sides of the chamber and the pressure does not rise high enough to either slide the case backwards or exceed the yield strength of the brass and stretch the case so the head is against the breech. Hence the case head stays forward where the firing pin pushed it, not getting pressed back over the primer. When the case is removed the primer is proud of the brass.


A number of things can compound this effect. One is excessive firing pin protrusion coupled with the heavy striker falls of these old rifles. The combination gets every bit of forward case movement available. A second player is a rough chamber surface, which allows the expanded brass a good grip and keeps the case from moving back.

90 grains of 2f is not a real light load and should be enough to push the case back. You might want to check the chamber finish. Since you have noticeable primer protrusion you have excessive headspace. In the case of a rimmed bottleneck case like this you can make a shim to fit around the front of the case rim, the shim being of a proper thickness to use up the extra headspace. When fired the case shoulder will be blown forward, filling the chamber. There after the case can be headspaced on the shoulder and you will have no further problems.

Best of luck,

Glenn

Thanks for the ideas. I'll bet the problem is a combination of mild pressure and maybe excessive headspace. Note that I have some loads from Gad Custom ammo formed from 28 ga brass. (they are a pc of junk IMO. I had some case separations at the neck and case neck splits.) The 28 ga rim is smaller and thiner than the Jamison brass. I had no primer problems with those shells loaded with the same bullets and charge. I did have some miss-fires, but I blamed it on the shell rim.

I did resize the brass before the 1st load using Lee dies. I wonder if they may be a bit undersized vs the dies that may have been used by GAD. The GAD shells could have been settling in on the poorly shaped shoulder while the Jamison could have been setting on the (excessive) rim space. What do you think?

PS I personally would not buy the shells from 28 ga brass again.

Also I want to load some shells with all copper to hunt pigs in our stupid Conder Restricted area. I was thinking about using .458 dia and patching with teflon plumbing tape. What do you think?

I might be able to find some .465 dia solids and just load those up. That is the diameter of the lead bullets I have from GAD. Any comments or thoughts?

Thanks

Jerry

PS The recoil from my loads was light, maybe lighter than the GAD ammo.

The Lee dies were built to specs researced by someone on one of the Martini boards; they were made to size cases to fit just about any nominally correct .577/.450 sporter or military chamber there is (Victorian era "standardisation" and manufacturing tolerances, you see), so they tend to size way down for most rifles.

Brass sized from brass shotshells (known as balloon head) has a different construction to solid drawn; there is more capacity in it, and is warned against use in rifles with loose headspace due to the possibility of rupture. There used to be a sticky post about the phenomenon on the Gunboards MH board; not sure if it's there still. I can't comment - I always use Bertram solid drawn 2nds.

I'd say a solid copper slug of .465" is too big. The nominal ususal bore diameter is .450, with groove depths out around .465". Not really sure though about non-tox bullets in such a rifle. There is a fan club of internet MH people who advocate relatively large diameter bullets in them to account for the taper bore. I'm not one; the bullet should upset and bump up to fill the rifling on firing.

Re: Recoil - from standing, kneeling or prone? I find standing and kneeling no problem with 90gr 1P and .462" 500gr gg. I'm flinching badly after a couple of rounds prone though!

What are you using?: Mk I-III, Mk IV, or something else?
RG