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Discussion Starter · #1 ·
I have made a 12 gauge insert to go in my scratch built 37mm ATG.
I custom made a breech block that cocks on opening, very similarly to the original.
i used an old single barrel shotgun for the chamber and was able to salvage and reconfigure the ejector. It kicks the spent hulls out like a champ!
I want to use it for WWII re-enactments. I filled some shotgun hills from primer to crimp with FFFG black powder.
I get a really loud report and a very impressive flash! The only drawback is the ton of white smoke.
Is there a fast burning smokeless powder that will give me similar results with less smoke?

Atmosphere Fire Flame Heat Gas
 

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Discussion Starter · #3 ·
Yes, I have been a War Between The States reenactor since 1995.
I’ve cleaned a blumillion black powder pistols, muskets, rifled muskets, and cannon in those 27 years.
i knew this was going to be messy.
i actually welded a .75” piece of tubing to the shotgun barrel and made a bushing on the muzzle end.
it directs the blast, sound, flash, etc all the way to about 2” from the muzzle.
 
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You have to restrain the smokeless loads much more than you do black powder. It needs higher pressure to speed up the burn rate so you'll get a boom instead of a hiss. Most blank powder used in rifles and pistols is pretty fast but as with any loading it will depend on your cartridge. Since your bore is so huge compared to the cartridge it will release the pressure fast. A longer insert barrel will help with that and you will probably need to use a heavy wad crimped or rolled into your shotshell.
As for powder you could start with something like bullseye or faster. Work your way up slowly and consider some sort of shredder or blocking plate to keep any wad or debris from being thrown forward. You're going to need to work this one out. Most of the shotgun blanks like those for the 10ga signal cannons are black powder or one of the fast burning substitutes like pyrodex or one of the others. They will require cleaning well just like black as you probably know from civil war reinacting....

Frank
 
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