powder variation & accuracy

stick · October 7, 2002, 12:13 PM

How much variation in powder charge from round to round can occur and still maintain accuracy? (Assume: non-maximum charges for safety reasons).

I've been using extruded powders in my rifles forever. Always trickled charges to weight after coming out of the Uniflow. Now I've been thinking: what variation in charge weight (average and extreme spread) could be expected by using a ball powder and not weighing/trickling each charge? And how much larger would my groups get?

I know not to expect the same match quality. Maybe good enough for pratice though. Any ideas or data.

Thanks.

dakotasin · October 7, 2002, 05:39 PM

i haven't been able to get away w/ not weighing powders since all my rifles are shooting extruded powders...

however, i have a theory!

i think that the amount of error you could get away w/ and still have acceptable accuracy depends on the amount of powder your case uses. my basis for this theory... the 7 mag consumes about 70 grains per shot. if i was off on my scale when i weighed the charge out by .5 grains, does it make much difference? no, it really doesn't. now, my 223 consumes about 25 grains of powder per shot. will .5 grains make a difference here? yep, it will.

something to think about: many 100 yard benchresters don't even bother to weigh their charges. their equipment is certainly top-drawer, but still, some don't weigh their charges, and they still shoot pretty good (competitive) groups.

so, my 2nd theory!! if you are only going to shoot 100 yards, it makes little difference if you are off a little here or there, especially if you have a standard hunting scope on your rifle (meaning the scope has paralax at 100 yards).

i think if you really wanted to test this idea, you'd have to bench shoot at 200 yards. at 200 yards, minor errors will tend to show up better; at 100 yards, minor errors sometimes don't show at all.

have you ever shot a group that measures .5" at 100 yards, and then tested it at 200 yards and got 2+"?

Khornet · October 8, 2002, 06:02 AM

that consistent volume is more important than consistent weight. That is, you set up a good powder measure to throw a given weight, and if it's a quality measure it will then throw all charges at the same volume tho the weight may differ some. This is why the benchrest people don't weigh after setting for a given weight.

Steve Smith · October 8, 2002, 09:20 AM

I think both these guys are right on the money. If you're shooting a little caliber, then pay more attention to variance...in a big caliber, I don't think it will make a difference at all.

I'll say this...I've shot several matches this year with great performance at 600 yards with my AR. I was always in a rush and never did any case prep at all, and used my Dillon for loading the ammo, including powder charges. Granted, I have top quality dies, but plain 'ol mixed lot LC brass. I was really amazed. Kinda goes to show that a lot of what we do isn't worth what we think it is.

BTW, I use RL-15 in that Dillon for the AR, and get a +/- .15 swing.

Bogie · October 8, 2002, 12:29 PM

You'll notice with many cartridges that as you go up in powder, your velocity spread will shrink. A full case means better accuracy, so find a powder which mostly fills the case, and just drop the powder with a measure.

Poodleshooter · October 8, 2002, 01:46 PM

To add to Bogie's statement, I've noticed that a full case tends to aid in accurate load formation, but I've also noticed that further increasing pressure in my guns (up to the level of sticky extraction) seems to decrease accuracy somewhat (though not as much as reducing loads).
This doesn't always seem to hold true with pistols. They seems more susceptible to "velocity windows" with given bullets.

October 7, 2002, 12:13 PM	#1
stick Member Join Date: September 6, 2001 Posts: 90	powder variation & accuracy How much variation in powder charge from round to round can occur and still maintain accuracy? (Assume: non-maximum charges for safety reasons). I've been using extruded powders in my rifles forever. Always trickled charges to weight after coming out of the Uniflow. Now I've been thinking: what variation in charge weight (average and extreme spread) could be expected by using a ball powder and not weighing/trickling each charge? And how much larger would my groups get? I know not to expect the same match quality. Maybe good enough for pratice though. Any ideas or data. Thanks.

October 7, 2002, 05:39 PM	#2
dakotasin Senior Member Join Date: June 22, 2002 Location: south dakota, U.S.A. Posts: 136	i haven't been able to get away w/ not weighing powders since all my rifles are shooting extruded powders... however, i have a theory! i think that the amount of error you could get away w/ and still have acceptable accuracy depends on the amount of powder your case uses. my basis for this theory... the 7 mag consumes about 70 grains per shot. if i was off on my scale when i weighed the charge out by .5 grains, does it make much difference? no, it really doesn't. now, my 223 consumes about 25 grains of powder per shot. will .5 grains make a difference here? yep, it will. something to think about: many 100 yard benchresters don't even bother to weigh their charges. their equipment is certainly top-drawer, but still, some don't weigh their charges, and they still shoot pretty good (competitive) groups. so, my 2nd theory!! if you are only going to shoot 100 yards, it makes little difference if you are off a little here or there, especially if you have a standard hunting scope on your rifle (meaning the scope has paralax at 100 yards). i think if you really wanted to test this idea, you'd have to bench shoot at 200 yards. at 200 yards, minor errors will tend to show up better; at 100 yards, minor errors sometimes don't show at all. have you ever shot a group that measures .5" at 100 yards, and then tested it at 200 yards and got 2+"? __________________ Hunting is not a matter of life or death. It is much more important than that.

October 8, 2002, 06:02 AM	#3
Khornet Senior Member Join Date: December 11, 2001 Location: NH Posts: 585	I've always suspected that consistent volume is more important than consistent weight. That is, you set up a good powder measure to throw a given weight, and if it's a quality measure it will then throw all charges at the same volume tho the weight may differ some. This is why the benchrest people don't weigh after setting for a given weight. __________________ The M1 does MY talking!

October 8, 2002, 09:20 AM	#4
Steve Smith Senior Member Join Date: December 9, 1999 Posts: 4,131	I think both these guys are right on the money. If you're shooting a little caliber, then pay more attention to variance...in a big caliber, I don't think it will make a difference at all. I'll say this...I've shot several matches this year with great performance at 600 yards with my AR. I was always in a rush and never did any case prep at all, and used my Dillon for loading the ammo, including powder charges. Granted, I have top quality dies, but plain 'ol mixed lot LC brass. I was really amazed. Kinda goes to show that a lot of what we do isn't worth what we think it is. BTW, I use RL-15 in that Dillon for the AR, and get a +/- .15 swing. __________________ Favor the X. Steve Smith NRA Life Member

October 8, 2002, 12:29 PM	#5
Bogie Senior Member Join Date: June 5, 2000 Location: Job hunting on the road... Posts: 3,827	You'll notice with many cartridges that as you go up in powder, your velocity spread will shrink. A full case means better accuracy, so find a powder which mostly fills the case, and just drop the powder with a measure. __________________ Job hunting, but helping a friend out at www.vikingmachineusa.com - and learning the finer aspects of becoming a precision machinist. And making the world's greatest bottle openers!

October 8, 2002, 01:46 PM	#6
Poodleshooter Senior Member Join Date: August 7, 2000 Location: Floating down the James River in VA Posts: 2,599	To add to Bogie's statement, I've noticed that a full case tends to aid in accurate load formation, but I've also noticed that further increasing pressure in my guns (up to the level of sticky extraction) seems to decrease accuracy somewhat (though not as much as reducing loads). This doesn't always seem to hold true with pistols. They seems more susceptible to "velocity windows" with given bullets.