doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Duplex load in a .410

A little background. I have been shooting muzzleloadrers for about 40 years. While I HAVE loaded and shot 12GA BP cartridges in the past, I would bot shoot long strings of shots, just a couple in the field hunting. I have zero experience with shooting BP cartridge in relatively long strings. Am starting with my 45-90 and have decided, based on what I have gathered in my search for info, to go with a duplex load as, from what I can gather, help burn out the fouling between shots negating/reducing the need to swab between shots. This leads me to my query, I took my .410 for a round of skeet yesterday. While I am a rather poor skeet shooter at the best of times, I did notice than my hits diminished toward the end of the round. Don't know if that was just me or if the fouling buildup in the barrels might have been a contributing factorCleaned the gun this morning and I could not believe the amount of crud that came out. As I said, I have been shooting MLer for 40 years so am not new to BP fouling but with ML'er, they basically get swabbed even time it is reloaded so fouling build up is always a minimum. Wondering if a duplex load would help and/or, what do others that want to shoot their BPC shotguns in events that require several shots do to alleviate the fouling issue?. I could take a squirt bottle of water and cleaning rod to run down every few shots but just wondering what others do when shooting black powder cartridges for extended clay games?.

For a very brief time, I experimented with duplex in my first .45-90. I decided it defeated the whole reason I was shooting blackpowder to begin with, so I stopped.

Later, Dick Gunn, a very well respected and knowledgeable BPCR shooter, did a deep dive into duplex rifle loads with some other folks. He found some evidence of sporadic pressure excursions that were very high. Given that the singleshot rifles we use are pretty darn stout, the danger seemed minimal, but it was not a good thing and even in normal operation it seemed that pressures were definitely higher - though no one had any loads actually pressure tested.

Duplexing is illegal for NRA BPCR and BPTR matches, and almost all other matches as well. Quigley may be a major exception, but even there, they are getting strict about types of loads do to several unfortunate failures.

Given that, there is no way I would ever shoot duplex in a shotgun without substantial pressure testing, and most (maybe all) people that pressure test shotshells will not test blackpowder. Maybe they will test a duplex load, but I am doubtful.

In any event, if you do try it, be darn careful.