frnkeore wrote on Jan 15^th, 2014 at 12:03pm:


Frank,
The Lyman Cast Bullet Handbook (3rd Edition) has some pressure data on duplex loads for .45-70 using SR-4759 and FFG. That's the only measured duplex pressure reference I've seen in print, so far. The duplex examples published here were for velocities in the 1250-1400fps range depending on bullet weight and exhibited pressures that were ~1200-1500CUP higher than equivalent-velocity charges of straight SR-4759. (Clear as mud?) I really wish that they would've published straight BP charges for comparison....

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Yes, you can indead shoot any kind of powder in ASSRA and ISSA but, I don't know of anyone placing very high in match results using BP in BR matches.

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Thank you very much for that info. I'll have to try and get that Manual. I don't consider 12 - 1500 a very large increase in pressure. I believe you could make up a lot of that increase with highly compressed BP loads.

40_rod, if your alluding to policing duplex loads, It's very easy when shooting BSed. A little harder if shooting multiple cases or fixed but, I doubt that there would be much if any cheating. The sound and amount of smoke would most likely give it away.

The accuracy level is just different with BP. The following are my match wining and club record targets, shot in the late 80's and early 90's with GOEX FG. All at 200 yards. The 237 2c was shot with my Clerke/Douglas 32/40, the rest are with my Hoch/Douglas, 32/35. None of those targets would have won a smokeless match and I've never seen any higher scores than my 32/35 shot, to date. But, BP shooting died out in my area and the only BP that I know of that's left is one that Joe (Westener) goes to in MT. Maybe Joe can relate what kind of scores are shot there?

Frank

Jeff_Schultz wrote on Jan 15^th, 2014 at 4:33pm:


You are correct! That's what I get for trying to totally recall something from memory. The velocity boost from the small charge of SR-4759 is somewhat surprising.