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Proof House Conversation

Rimfire, centerfire or black powder related topics

Proof House Conversation

Postby Shootist » Fri Apr 20, 2018 8:24 pm

I have a .44 Pietta Colt Cattleman single action muzzle loading black powder revolver. I bought it second hand from a chap that had removed the original nipples from the cylinder and replaced them with nipples that take shotgun primers. From various discussions I now have reason to suspect that this pistol will happily cope with a nitro load of about 5 grains of Bullseye. I telephones the Birmingham Proof House and spoke to one of the supervisors there about the possibility of getting the pistol proofed for such a load. At first he seemed to think it was OK but then changed his mind to say he doubted it could be done.

Apparently, the reason it could not/ would not, be done was that if proofed for 5 grains of Bullsey, the chambers could be filled with a significantly greater quantity of Bullseye which if fired might dismantle the pistol into it's component parts and distribute them around the area. There was no suggestion that the 5 grain Bullseye load would of itself be unsafe.

The logic of this seemed to deserve more thought. Consider, my Savage .308 has been proofed. I load it with a max load of 46 grains Viht N140 and that's about OK pressure wise.OTOH, a 100% load of Bullseye, things are definitely not alright. Some other powders, according to Quickload, are much much more not alright.

I am starting to wonder about the whole proofing thing. Sure, some testing needs to be done, but I would like to think that any testing would have a rationally thought out basis.
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Re: Proof House Conversation

Postby Keef » Fri Apr 20, 2018 9:52 pm

Your nitro cartridge firearm goes to proof and is fired with the standard cartridge loaded to produce a chamber pressure that is above normal loading. I can't remember (if I ever knew) by how much but 10% is stuck in my mind.

The powder used will be one where the powder fits in the case and the bullet seats normally. The type of powder and volume will give a known pressure so that your firearm is tested to a specific excess pressure and to past proof there must be no rupture of the chamber/barrel.

If you use a powder with the wrong burn rate or excessive volume of powder then chamber pressure may exceed the design limits of the firearm and the pressure at which the gun has been proofed with possibly catastrophic results.

Your blackpowder pistol has been probably been proofed with sufficient blackpowder to fill the chamber leaving sufficient room for a bullet. As it has a full chamber you would not be able to exceed the proof load.

However if you use a nitro powder it would be easy to put sufficient powder in the chamber to vastly exceed the safe working pressure.

Unless there is published load data for the various types of powder for use in muzzle loading pistols then any load you use is going to be guess work as to the safe level you can use.

If the Proof House is not prepared to do a test it implies that they do not have a reliable load to test with.

A quick look on the net will provide plenty of images of firearms shot with cartridges using the wrong powder or excess load.
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Re: Proof House Conversation

Postby flintlok » Sun Apr 22, 2018 5:02 pm

I wouldn't want to push my luck with Bullseye powder in a black powder pistol. I know of fellows who use black powder cartridge combination loads with a few grains of fast burning smokeless at the base of the load topped off with a full case of black powder in cartridges such as the 45-70 and 50-70. It's supposed cause less black powder residue in the bore. I haven't tried that technique, I really don't like mixing powder and guns but if there were no alternates powders I possibly may. Thankfully, I have both types powders.
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