Firing The Thunder Mug
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It's a Tradition to shoot the Thunder Mug every 4th of July. Been doing it since the early 1990's other than the years we were in Mozambique.
120 gr. of 3Fg plus 200 gr. of Pyrodex P wadded tightly with fine steel wool.
The blast shoved the Thundermug into the ground
4 or 5 inches.
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That's quite a load! Researching my BP Cannons
for actual projectile firing; it's recommended that the projectile is loose in the bore (0.100" minimum suggested), they call it "freebore". This is the smoothbore shooting. The ball is shot out like a pea shooter. My 3# balls are about 0.150" undersize.
The suggested charge, max. load for hard projectiles, is 1 oz., by volume - 427 grs., per inch of bore size. They say use only "coarse cannon grade powder". I take that is must be more chunky than Fg. Most guys make their own powder these days. I usually reduce the charge drastically and use commercial FFg. or equivalent. Both my Hern Iron Works MT guns, I bought through Dixie Gunworks, are 2.25" bore guns. I like to use 700 grs. charge so I can get 10 shots per lb. One is on a sled, the other larger gun is on a "truck" with wheels. Free recoil is 10-12 ft. Left to right sighting is pretty good but elevation is a booger.
I have loaded it completely full of 3Fg
with a solid lead slug bore diameter and about 2" long hammered down on the charge, compressing it. I fired it and watched the slug go up out of sight, then caught sight of it coming down about 300 yards away. After searching awhile we found it.
Long ago I saw a Lyman test on BP failures
They took a .58 barrel and filled it totally full of powder with a bullet packed at the muzzle. It fired without incident. The same test with 150 gr. charge exploded, the charge at the breach and a "short started" bullet at the muzzle.
That's why they had all those cork and felt filler wads in BP cartridges and shells! Loose BP blows stuff up.
Even the cannon charges are in "cartridges" I use plastic baggies encased in tin foil. You use the "prick" to poke a fuse hole in it before lighting. Plastic won't light afire. I do fret over static though. I used newspaper for wadding ONCE! lol We had a time stomping out all the smoldering fires!
Fires
We always figured if we didn't set a pasture on fire we weren't doing it right. 
Sir Boggs. That’s quite scientific
Wow. We have the same cannon. We use different techniques. I have never used a prick, I just put 1/2 C of cannon powder in the bore and pound a piece of firewood (or panties) in the end. I do wait 15 minutes before doing it again.
Recently I’ve added 1/4 C of titanium shavings. Makes a fun fireworks display. I rarely find the firewood. I assume it’s blown to splinters.
Last winter we pounded an 8 ft live tree in the barrel (7 1/2 sticking out)For good measure I doused it with gas and lit the cannon. The blast blew out the fire, all the limbs dropped straight to the ground and the tree less branches flew about 300 yards. 
Well done… see the picture
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