Need Reduced BP loads for 38-55

Snider shooter said:
No way are you going to over pressure with black so stop worrying.
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Not true according to the US Navy. Although I do agree that it is hard to do at our level, a dangerous pressure level can be attained with an older weaker action. The U S Navy conducted very intense BP pressure tests with modern testing equipment aft a couple of their sailors got into a tiff and blew a turret off one of their battle ships. They concluded BP pressures of up to 200,000 foot lbs can be achieved just by regulating a very tight projectile to bore relationship. Im not saying you or I will ever achieve 200,000 lbs pressure but even a modest increase up over 30,000 can stress some of our guns and I warn that that might be achievable by an unknowing soul.
After the Navy test, A now closed publication "The Artilleryman" that keyed on Cannoneering south of the border did a test on cannon pressures with modern testing equipment and discovered the Navy test had a lot of merit. They could regulate pressures in a 3" bore tube from 20,000 up to over 30 just by using a different projectile (tighter or heavier).
 
fiddler said:
Is there a particular book you're looking at with those speeds? I have 3 different books and the charts are quite limited and not much over 1400fps with jacketed 255gr.
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1700 fps can be attained with smokeless powders, I don't think I would do that in a 1881 but my 93's don't seem to mind. A case full of FFG shows with the 225gr cast bullet a CUP of 8700. With the 255gr jacketed @ 1750 CUP is 27,700.

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It is true that the U.S. Military somehow managed to get very high pressures with BP, I just can't see it happening in anything close to a normal load. In Campbells books on the Winchester Single Shot he makes mention of a very high velocity/pressure test done.

The only published data I've ever seen that indicates even moderate pressures was when one of the smokeless powder companies published load data for the 50-140. They wanted to limit pressure to black powder levels so tested it first. To be honest I do not remember the number, but it was well under 40k psi which is a fair bit, but that is an enormous case that does actually hold a full 140gr of powder. I've heard of numbers for the 45-110 being around 30k range for a full case of Swiss and a heavy long range bullet. That was on the Shiloh forum a long time ago and from anything I've ever seen published, I think it's way high.

With respect to the 38-55, the case really doesn't hold much powder. In a single shot rifle in good condition, you don't have to fear loads of FFFg over a heavy bullet. Not sure about weaker actions, but it's certainly done all the time in various reproductions.

Quite recently someone on the ASSRA forum did a bunch of pressure testing for BP. I will see if I can dig up the link.

Chris.
 
Somehow, I get the impression (maybe incorrectly) you’re looking for a reduced load - by using BP - rather than a “reduced BP load”. Here’s why: a reduced load in a fixed volume casing implies a less than full charge … and that means there’s an air space between the powder and the bullet. Not good. It follows, then, that if you want to use BP, you must ensure the bullet is pressed against the powder. I sometimes use BP in my 30/30 and 30-06. I just fill the shell as much as it takes to allow the bullet to seat to the crimp groove and - bingo - there’s my reduced load. Thimpo.
 
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