577-450 Duplex

[Gunfreak25]

I have a literal lifetime supply of Unique. Don't ask. I also make my own blackpowder, milled, wetted, pressed with a 12 ton press into pucks, dried, corned and screened to 1F size. Shoots great, but a real chore to make. It fills the 577/450 case very well being a little coarser in grain size. It is every bit as powerful and dirty as plain 2F Goex.

Anyway. Looking to clean up the burn a little bit and the obvious choice was my 15 pound supply of Unique. I use anywhere from 400-500 grain bullets, some grease groove some patched.

I was GUESSING that 10 grains of unique to 60 grains of 1F black might be a place to start. Maybe less unique and more black?

What say's y'all?

[Larry Gibson]

The use of a smokeless powder charge under the BP does not really make the BP "burn cleaner". The job of the smokeless powder is to blow the ash residue out of the barrel (charcoal is partially burnt wood and the black streaks of fouling is ash). I use extruded smokeless powders such as 4759 (preferred) up through RL7. Unique may be too fast burning raising psi's before it gets the job done. Unique did not work for me in the 45-70 with 405 gr cast bullets.

I suggest starting at 3 gr Unique and subtract 1.5 gr BP for each grain of BP used in your normal BP load. Work up in 1 gr increments of Unique again subtracting 1.5 gr BP for each gr of Unique used. Shoot at least 5 shots of each increment. Inspect the bore after each increment. You should see how far up the bore each increment is pushing the BP fouling (black streaks of ash). Stop with the increment that pushes the fouling out the end of the barrel completely. There will still be some fouling from the lube etc. but you should be able to see the difference.

Ensure in your incremental loads there is still sufficient compression to hold the powders in their respective places to prevent migration of either powder.

Also chronograph each increment. If the velocity of any increment exceeds that of the normal straight BPs velocity STOP.......you are exceeding the psi of the BP load. If this happens then Unique will not work and you need a bit slower powder. Since 4759 is no longer available I suggest 4227 or RL7. Some use 3031 but I have not duplex tested that with BP so can not advise.

Remember, sometimes what we want to use (because we have a lot of it) in an application may just not work or be wise.

Larry Gibson

[Gunfreak25]

I appreciate the response, Larry. Not an easy question but you answered it very well. I believe RL7 is next on my powder list, new sportsmans warehouse just opened here so my choices have expanded a lot. I'll probably save the unique for my 50 yard 14 grain plinker loads.