Load for Navy arms double full

[Barkiller]

I have a double Navy full choke I bought in the 80s. Said 85 grains power Max. I've been using ff powder and have not been able to work up a very good load. I tried 85 grains of fff and it shot great. Anybody know if this will damage the gun or have any experience doing this. I've used many different wad combinations trying with the ff to no avail.

 

[SlidePicker]

The traditional 3 drams powder load in 12 gauge unmentionable inserts is about 82 grains. 85 grains is a perfectly acceptable load, with 1 to 1+1/4 ounces of shot. Generally, though, FFg powder is recommended in 12 gauge muzzleloaders. Goex lists FFFg in their blackpowder shotshell loads.