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Doc Hoy · March 12, 2012, 09:30 AM

The formula is interesting.

My question had to do with my observed variation in Muzzle Velocity. I use a CED chrono.

I am recalling these figures from memory but I think I am close. I have to shoot about 30 rounds to get a good idea of the average MV. On a system (I define "system" as one revolver on a given day with all shots fired in sequence so as to reduce the time differential, same powder charge, same powder from the same container and same bullet casting run. Barrel swabbed after each round of six. All chambers loaded) in which average MV is 750, I might get a standard deviation of 40 FPS if I am lucky.

I am fairly careful with measuring the charge as I use that contraption I came up with last year so I may not know the exact weight of the charge but I know that all charges are very similar in volume. I think I am getting very close to the indicated charge plus or minus one grain. I mold my own round balls and can get standard deviation in diameter down to less than .001. I think I am at least moderately successful at reducing variation in the factors contributing to the formula. Yet if SD is as I have observed, I get as much variance from shot to shot because of unidentified factors than I would if I randomly chose a different powder. Both factors equal about 95% to 105%

March 12, 2012, 09:30 AM	#6
Doc Hoy Senior Member Join Date: October 24, 2008 Location: Naples, Fl Posts: 5,440	Agree The formula is interesting. My question had to do with my observed variation in Muzzle Velocity. I use a CED chrono. I am recalling these figures from memory but I think I am close. I have to shoot about 30 rounds to get a good idea of the average MV. On a system (I define "system" as one revolver on a given day with all shots fired in sequence so as to reduce the time differential, same powder charge, same powder from the same container and same bullet casting run. Barrel swabbed after each round of six. All chambers loaded) in which average MV is 750, I might get a standard deviation of 40 FPS if I am lucky. I am fairly careful with measuring the charge as I use that contraption I came up with last year so I may not know the exact weight of the charge but I know that all charges are very similar in volume. I think I am getting very close to the indicated charge plus or minus one grain. I mold my own round balls and can get standard deviation in diameter down to less than .001. I think I am at least moderately successful at reducing variation in the factors contributing to the formula. Yet if SD is as I have observed, I get as much variance from shot to shot because of unidentified factors than I would if I randomly chose a different powder. Both factors equal about 95% to 105% __________________ Seek truth. Relax. Take a breath.