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.
 
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