A small amount of smokeless powder results in better combustion of the black powder resulting in cleaner fouling.

When you are not allowed to use duplex loads; you can use magnum primers to accomplish the same task.

The practice was quite common before the advent of reasonably priced longer cases for the .45s in LR shooting.  Nearly everyone was shooting a .45-70 with duplex using  about 10% smokeless by weight. 4227, 4759 and Reloader 7 were quite common. 

Caution:  25% smokeless can  raise the pressure and be quite dangerous.

I've heard stories that I could shoot duplex loads and not have to clean the bore and shoot just like I was using smokeless.

I tried it a couple of times with 10% SR-4759 and to be honest I didn't really see the bore being much cleaner than with 100% black powder.   Maybe I did something wrong 

Chris.

gunlaker wrote on Jan 6^th, 2019 at 11:48am:


I think Reloader 7 and maybe a few others I do not recall were a little better than 4227 and 4759.  Everyone did it.  Nobody shot straight BP and nobody wiped the bore or used blow tubes between shots that I recall. Bill Crane told me use just enough smokeless to clear the bore. 

When  I got my .45-2.6 to shoot straight BP in LR, it didn't seem to want to shoot.  I loaded up some duplex to see and it shot very well.  I kept working BP until I figured it out.  Of course, in those days there were only a few local rumors about how to do it.  No www advise yet     

Tom Selleck fixed all that withr Quigley Down Under in 1990 and Al Gore invented the immermett to distribute the load data  and advise   I wish I had known about the advantages of PP bullets in LR shooting.  The only 2 guys using them could not compete with the grease groove shooters but most of our matches were limited to 600 yards.  Only Douglas Ridge in OR made 800 and Heals at Victoria, BC had 1000.  WE did have a few 1000 yd shoots at KD 22 on Ft Lewis, but the military was impossible to deal with so they were no very many.  One of the PP shooters was shooting groups bigger than the target frame a 1000 

The reason I started to shoot straight BP in LR was at the shooters meeting at Ottawa in 1993, the Brits said if they were going to shoot any more world competitions it would have to be straight BP.  All but one of them were shooting original muzzle loaders. They placed 3rd.   The Americans were 2nd shooting buffalo style guns with duplex and windgage front sites.  The Canadians won shooting Martini target rifles, heavy loads of duplex and Australian Central receiver mounted target sights.  Tom Matpack of the US team was high individual because of his phenomenal wind reading ability.  His shooting pardner, Chuck Virgin, was 2nd high individual.  Clearly, equipment and duplex won the day in the team competition. 

I think I did get my .45-2.6 with straight BP to shoot slightly better than my .45-70 with duplex but I do not have any group measurements for comparison.   ............continued.........