View Full Version : .50 pressures

October 8, 2010, 02:24 PM
Does anyone know the pressure that 60gr of black powder pushing a .49 roundball? Or a site that has a caculation table?

Andy Griffith
October 8, 2010, 05:08 PM
No way to know exactly without a pressure transducer on the specific gun. Another gun will give different pressures. Is this in a rifled bore or smooth bore? Patch thickness, type of lube, rate of twist, number of lands and grooves, temperature, humidity, elevation, brand of powder, granulation of powder....
Heck, some fellers might do some checking of the stars and call their local witch doctor.

All joking aside, you'd need a transducer on the rifle in question. All I know is that black powder pressure curves are much different from their nitro counterparts- and it is the curve of that pressure that matters just as much as the pressure itself.

Someone else more educated on the subject will be along shortly. There is an average accepted maximum pressure I'm certain, but I don't know what it is. I doubt there is a SAMMI spec for muzzleloading barrels, at least I've never heard of one.

October 9, 2010, 08:01 AM
Lyman did a bunch of pressure testing and published the results in their black powder loading manual.

28" Douglas barrel, bore .503, groove diameter .526, twist, 1 in 66".
.498 round ball and .015" patch lubed with Crisco.

60 grains Goex FFFg, 8,100 LUP, 1460 fps
60 grains C&H FFFg, 4,900 LUP, 1390 fps

60 grains of black powder is a very light load for a .50 caliber rifle, it may be too light for optimum accuracy. Squib loads are usually not accurate in muzzle loaders. Also, the velocity being right above the speed of sound is the worst possible velocity as far as wind drift is concerned. Shoot em faster and you get less wind drift, shoot them slower and you get less wind drift.

Also notice that the brand of black powder made a huge difference.

Andy Griffith
October 9, 2010, 11:16 AM
I've shot a lot of matches and usually the limit on powder grains was caliber +10.

October 9, 2010, 12:47 PM
I've shot a lot of matches and usually the limit on powder grains was caliber +10.

Is that a local club rule? Most of my competition shooting is with the Texas Muzzleloading Rifle Association and they have no powder limit in any of their matches except for the short range metallic silhouette targets, to keep people from destroying the targets.
Some of the unlimited bench rest shooters load up to 200 grains of powder in their .60 caliber heavy bench rest guns. Makes car alarms go off.

Andy Griffith
October 9, 2010, 04:21 PM
All the matches that I've shot in south western N.C. and Georgia have this rule, with exception of long range matches which only one or two have the length to hold, so most are 75-100yds. Also, round ball only in the bullseye matches out to 100 yards. Long range matches- anything goes but there are so few long range matches in this area and...that's the way its been done for so long. I've shot these matches for fun but but I was terribly outgunned by some serious bench guns that could cut bullet holes.

I agree that the bullet might need to be salted before it gets to the target so it won't spoil, but this the game they play.

October 9, 2010, 10:26 PM
Come to think of it, the caliber + 10 rule on maximum powder charge should tend to equalize different calibers. The guy shooting a .32 caliber squirrel rifle is allowed to use 42 grains of powder. His powder charge nearly equals the weight of a .310 round ball (45 gr) and that should result in a muzzle velocity of around 2200 fps.

The guys shooting .50 caliber rifles can only use enough powder to get about 1300 to 1400 fps.

The guys who shoot .58 caliber rifles can only use enough powder for about 1000 fps.

The tendency of the larger calibers to drift less in a cross wind becomes offset by their lower muzzle velocities.