doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com High Energy Black Powder Loads?

A friend of mine told me that some 12 gauge black powder loads (and some Brown Bess loads) can exceed 2500 ft lbs of energy. I was not aware that black powder could make that much power. Most black powder loads make between 1,000-1,900 ft. lbs. What's the truth?

They certainly could. I load a 10 gauge with 1 1/2 of shot (656 grains) and 4 1/2 drams (122 grains) of 3F black powder. This load has a muzzle velocity of about 1300 fps. Using a energy calculator (https://www.beartoothbullets.com/rescources/calculators/php/energy.htm) this load has an muzzle energy of 2,462 lbs.

A Brown Bess uses about a .715 ball (550 grains). You would need to push that ball at about 1431 fps to reach 2,500 foot-pounds of energy. I don't know what the powder charge would be for that, probably somewhere in the 130-150 grain range of powder. Certainly a very stout charge, but not astronomical.

So yes, it is very possible, but I would certainly only want to shoot that in a gun that was specifically built to handle it. The recoil would be, shall we say, unpleasant.

Note that ft lbs is not fps. Ft lbs is a function of mass and velocity which is called kinetic energy. A 1/2oz 12 ga slug is .03125 lbs and assume its velocity is 1200 fps.

1/2 x (.03125 / 32.2) x (1200 fps x 1200 fps) = 698.75 ft lbs.

Whoops that is a light slug. Lets change that to a 1.5 oz slug = .09375 lbs

1/2 x (.09375 / 32.2) x (1200 fps x 1200 fps) = 2096 ft lbs

So there you go.

Thanks guys! Seems like you could load a 600 grain slug into a flintlock and have a hard hitting weapon. I wonder what the pressure would be on something like that.

I once shot a 237 grain .54 cal. patched round ball out of my .54 cal. Leman Trade rifle, with a 1 1/16" barrel, ahead of somewhere around 240 gr. of Goex ffg. Accidentally!! I won't go into how the accidental loading happened, but it did not involve alcohol, I promise.

I have no idea what the foot pounds of energy was on that load, but the tang sight recoiled into the bridge of my nose and laid it open like a knife. In retrospect I believe it would have killed any living thing it was aimed at. It nearly got me. But, no harm whatsoever to the rifle.

SRH

Stan,
Sounds like you accidentally doubled up on the powder. I use 120 gr. of ffg with a 250 gr. slug in my Hawkens.

More than doubled the intended load, Tamid. I was shooting a 100 yard match, and listening to a joke being told while loading.

I guess I proofed it that day.

SRH

Ft Pounds are dependant on several factors, including projectile weight. To try to put a limit on how many can be produced using black powder is a bit ridiculous.
What for instance would be the foot pounds produced by an 1860's era 25 pounder black powder cannon.
To make it a bit more relative & limit it to shoulder fire sporting guns how many were delivered by the old 8 & 4 bore black powder rifles, some of which burned as much as 16 drams of powder.

Ft Lbs are a factor of mass (weight) and velocity and nothing else. If you can measure both variables you can calculate the ft lbs. I don't know what black powder has to do with it.

Correct;
The formula is �MV�. Thus that 25 lb cannon ball would only have to fly about 80fps to reach 2500 ft/lbs energy. The 4oz ball of a 4 gauge would have to make just a tad over 800 fps. Both are quite capable of obtaining higher velocities using Black Powder as the propellant.

Let's say you have a 12 gauge gun and want to shoot a heavy charge with a 600 grain hard cast slug. (Assume recoil isn't an issue, although I imagine recoil will be stout). 150 grains would roughly equal 2500 ft lbs. Would 200 grains equal 300 ft pounds? Does anyone know what the approximate pressure would be?

It seems like 150 grains in a 72 caliber with an equivalent weight bullet would manage more energy than a 150 grain charge in a .45 or .50 caliber rifle. Is this due to the different burning dynamics of black powder? (Does the wider cross sectional area allow more of the powder to burn?)

Velocity is obtained by applying force to the base of the projectile. The velocity is of course proportionate to the amount of force as well as the area of the base.
The areas of bullet bases are relative to the square of their diameters. (.72/.45)� = 2.56. Thus if you had an exactly identical pressure curve a 235 grain bullet would be pushed to the same velocity in a .45 as a 600 grain one in the .72.
A 500 grain bullet (old government weight for the .45-70) would have to reach 1500 fps to develope 2500 ft/lbs, a 600 one 1370 fps. It would take a good bit more pressure to get that 500 grain bullet to 1500 fps from a .45 caliber barrel than to get the 600 one to 1370 in a .72 bore.