Black powder pressure

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Easyrider

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Does anyone have reliable information about what sort of pressure black powder develops? I'm interested in both muzzle loader, and BPCR. The muzzle loader is a Pedersoli Gibbs, shooting 100 grains of 1 1/2 Swiss, behind a 520 grain cast bullet. The BPCR is a Shiloh Sharpes 1874, in 45/90. 85 grains 1 1/2 Swiss, and 535 grain cast bullet.
Any guesses what effect a 5 grain smokess duplex load would have?
 
I can't tell you for your loads, but the highest published pressures I've seen for a long range black powder rifle were in the 30k cup range. I don't remember the cartridge but I think it was either a 45-110 or a .50-140. I think the typical long range load for a 45-90 would be a fair bit less.

Unfortunately I can't find it in any of my books right now. Maybe Hatcher's book would have some numbers on the .45-70 at least.

No idea about duplex other than more. I don't play with it as no match I have been to allows it. I used to have an older version of the Lyman Cast Bullet Handbook that had duplex bp loads in it. They might have pressure data, but it's definitely not in the latest edition.

Chris.
 
Thanks, Gunlaker. I haven't found much either. I use the duplex.loadas to simplify bore cleaning between shots. I shoot paper jacketed buets, so the cleaner the better. It helps a lot. I'll worry about matches when I enter one...
 
lyman bp handbook ..and loading manual second edition.......45 90 535 gr cast...goex 70 gr...cup 11500......pyrodex 70 gr /vol...19900 cpu...............pages of ml bp loads and ctg loads with cpu vel eng ....etc......lots of good stuff......its a sam fadala writing published by lyman......second edition....don
 
Why shoot with duplex loads? BPCR rules for silhouette and target as well as MLAIC rules for muzzle loaders do not allow for duplex loads in competitions. Might as well practice with what you will compete with.
 
Easyrider, I did a little more digging. I think the 30k cup number I saw was from reloading data for the .50-140 Sharps. IIRC one of the smokeless powder companies did some testing of the .50-140 to get baseline pressure data, and then made smokeless data to match the pressures. I owned one of these monsters for a while and I can say that 140gr of Goex Fg and a 700gr bullet does not make for a lot of fun.

I'm surprised that the .45-90 data with 70gr Goex was only 11,500 cup. Mind you that is a pretty light load and a relatively weak powder. I imagine a heavier load of Swiss would be somewhat higher, but I doubt it'd be double. Interesting.

Chris.
 
Easyrider said:
Does anyone have reliable information about what sort of pressure black powder develops? I'm interested in both muzzle loader, and BPCR. The muzzle loader is a Pedersoli Gibbs, shooting 100 grains of 1 1/2 Swiss, behind a 520 grain cast bullet. The BPCR is a Shiloh Sharpes 1874, in 45/90. 85 grains 1 1/2 Swiss, and 535 grain cast bullet.
Any guesses what effect a 5 grain smokess duplex load would have?
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I fear for your future. I see you're in Manitoba so I'm not likely to have to worry you're shooting in the lane next to me.G:
 
Ya, that's my thinking, Chris. I'm here to tell you, the 45/90 is plenty of gun for my old shoulder! That said, I like it, and I'm starting to get it shooting pretty well. The Gibbs is more challenging. It needs 100 grains to "bump" the bullet to groove size. Anything less is pretty erratic. Grease groove bullets won't shoot at all...they tumble.
 
Perhaps I should explain my thinking re: duplex loads. I am attempting to work up optimum loads for both the Gibbs, and the Sharpes. Duplex loads help tremendously with keeping a clean bore. I wipe between shots, as well. I figure that if I can get maximum accuracy, with a clean bore, then when the time comes to shoot regular BP loads, I will have a baseline to work with. As for 5 grains of smokeless being dangerous, l don't bieve that for a second. As Chris mentioned, 140 grains of black have to develop way more pressure than 100 plus 5 grains smokeless. Furthermore, the 45/90 brass never show signs of excess pressure. I been shooting and reloading a long time, and with great respect, I have some idea what I'm doing.
 
Easyrider said:
Ya, that's my thinking, Chris. I'm here to tell you, the 45/90 is plenty of gun for my old shoulder! That said, I like it, and I'm starting to get it shooting pretty well. The Gibbs is more challenging. It needs 100 grains to "bump" the bullet to groove size. Anything less is pretty erratic. Grease groove bullets won't shoot at all...they tumble.
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Easyrider, If your GG bullets in your Gibbs are tumbling could mean one of two things; the bullet diameter is too small. My are sized to .449 with a .4495/.450 bore. It also could be your bullet is not bumping up. This could be too hard of an alloy or not enough powder. I am using 1:25 alloy. Are you using any wads below the bullet? Place a .060" fiber wad below the bullet to protect the base. if the base gets gas cut to much it can tumble. I use Swiss 1 1/2 powder. We also use magnum caps. Hopes this helps you.
 
MC One Shot said:
Easyrider, If your GG bullets in your Gibbs are tumbling could mean one of two things; the bullet diameter is too small. My are sized to .449 with a .4495/.450 bore. It also could be your bullet is not bumping up. This could be too hard of an alloy or not enough powder. I am using 1:25 alloy. Are you using any wads below the bullet? Place a .060" fiber wad below the bullet to protect the base. if the base gets gas cut to much it can tumble. I use Swiss 1 1/2 powder. We also use magnum caps. Hopes this helps you.
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Thanks, MC. I am using 1/38 tin/lead, brinnell hardness 8 alloy. That's why I'm asking about pressure. The bullets measure .449 as cast, the bore is .450. They slide.down the bore with the weight of the ramrod, if the bore is clean. I have used both thin fiber wads, and thick, up to 3/8". Paper patched bullets shoot more consistently. They cast .440 and are .450 wrapped. Both bullets require 100 gr of Swiss 1 1/2 to bump. I would like to shoot less powder, to reduce cost and recoil, but that would require softer alloy, and gas cutting is a concern. Hence the pressure question.
 
I'm surprised that your Gibbs needs 100 gr of powder to bump up, but I've never shot a muzzleloader. Is the rifling quite deep? I have a few rifles for shooting bore diameter PP bullets, and at least in the .45-70 I've gone as light as 77gr of Swiss Fg with a 535gr Money bullet in 16:1.

I know that in the early days of precision muzzleloading, bullets were sometimes cast in two pieces, with a soft alloy for the base, then swaged together with a hard alloy nose :)

Chris.
 
gunlaker said:
I'm surprised that your Gibbs needs 100 gr of powder to bump up, but I've never shot a muzzleloader. Is the rifling quite deep? I have a few rifles for shooting bore diameter PP bullets, and at least in the .45-70 I've gone as light as 77gr of Swiss Fg with a 535gr Money bullet in 16:1.

I know that in the early days of precision muzzleloading, bullets were sometimes cast in two pieces, with a soft alloy for the base, then swaged together with a hard alloy nose :)

Chris.
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The rifling is not particularly deep. I suspect that MC One-shot was correct, the grease groove bullets are slightly undersized, although they seem correct to me. The PP ones are better, so I'll go with them, I guess. I prefer pp anyway...less messy.
 
Easyrider said:
Perhaps I should explain my thinking re: duplex loads. I am attempting to work up optimum loads for both the Gibbs, and the Sharpes. Duplex loads help tremendously with keeping a clean bore. I wipe between shots, as well. I figure that if I can get maximum accuracy, with a clean bore, then when the time comes to shoot regular BP loads, I will have a baseline to work with. As for 5 grains of smokeless being dangerous, l don't bieve that for a second. As Chris mentioned, 140 grains of black have to develop way more pressure than 100 plus 5 grains smokeless. Furthermore, the 45/90 brass never show signs of excess pressure. I been shooting and reloading a long time, and with great respect, I have some idea what I'm doing.
Click to expand...

While most competitions do not use them, the place that you can look to for info and direction on Duplex Loads and their effects is likely to be over on the ASSRA Forums, where there is a lot of guys that are very knowledgeable about such, as they were pretty much state of the art back in the era when guys were competing with the likes of Harry Pope, and his peers.

IIRC, the upper limit for a duplex load was said to be about ten percent smokeless powder, before things got out of hand. I do know that there were several makers of powder measures that had both the smokeless and BP in them, for loading cartridges at the firing line, using breech seated or muzzle loaded bullets.
 
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