duplexing Black powder

[mdeland]

Have any of you ever tried and tested dulplexing black powder ? I've tried it a few times to see if it works but have not gotten around to serious testing and chrongraphing the results. I wonder if it could boost velocity in a 45-70 and still maintain standard deviation and uniform pressures.
It did work well for me with no signs of pressure spikes but seemed to foul up faster than a standard load when using only a blow tube.
I used some Meal-D I think it is called which has the fineness of dust and is used for pan flash in flint lock guns.

[bohemianway]

I use it in a 45-120 7gr 4759 balance Black (Goex CTG), 475 gr GG, and it really cleans it up. I can shoot 20 rounds without cleaning, before it was three rounds max. However, It really flattens out the primers so my guess is this is pushing it. It is a Shiloh Business rifle which is a testament to their strength. A P.O. had not noticed a case separation which stuck in the bore right in the front of the chamber and shot numerous rounds through it. Just imagine a slug of .457 going through a choke of .430 in a 45-120. As for accuracy I do not know but it did clean up the burn significantly.

[mdeland]

I'm talking about different granulations of black powder in a load not smokeless duplexing which I use regularly in cold weather match shooting.

[Clarence]

20+ years ago, Elephant sent our club in Baton Rouge a case of Elephant powder. It turned out that it had not been properly dried, and normal loads in .45-70 barely cracked 1000 fps. They replaced the case with one dried properly. In an attempt to salvage the wet case, I loaded some rounds with 6 gr. of DuPont 4Fg. It brought the velocity up to something acceptable (don't remember exactly, but similar to the DuPont FFg I was using at the time.

It shot okay. I shot several matches, getting scores similar to me norm at the time. I don't remember any particular issues with fouling, but it has been over 20 years... I sold most of the remaining powder to a re-enactor who only cared if his rifle went bang.

Clarence

[Glen Ring]

I've wondered about all that trying to get THE load. From what I can glean from folks in the know, BP burns fast. When trying to get the burn rate slower and more consistent, they use pistol primers and even paper over the primer.

One reason I use Pyrodex. It has a slower burn and there's not a big flash out of the barrel. I assume that the Pyrodex has been consumed inside the gun , but I have no way of knowing that and I don't have a chronograph anymore, so it's a guess.

I do have some old loading manuals that list duplex loads using BP and smokeless...but I've never tried one.

[mdeland]

In reading Ned Roberts book of percussion match rifles, which of course was all black powder fueled, they knew even back then that black powder usually responded best, accuracy wise, with low brisance caps.
Mann discovered that the whole powder column does not ignite simultaneously and was still burning several inches up bore. This means that the front of the column compresses against the wad and bullet base before finally burning.
If the fine powder is at the rear of the charge than it should ignite faster and develop more pressure per grain thus enhancing the efficiency of the rest of the charge burn rate. It seems like it ought ought to increase velocity and in a contained brass case in a strong rifle, do so safely.
This idea of course is not new as some artillery uses black powder to ignite the smokeless charge.

[semtav]

If you really want to screw with DD's mind, come up with a half Swiss, half OE load !!
But you can only shoot it at paper targets or funny little animals !!

[mdeland]

I've tried black powder on black powder duplexing in both my 38-70 and 45-70 to see if it works and it did safely in both but what needs done is some real accuracy testing with chronograph input. If one could get say 1300-1350 fps and low SD's with 500 + grain bullets in a 45-70 it probably would help in the long range department.
Most 45-70 loads with 500 + grain bullets are really struggling to get 1250 fps I'm thinking.