Dirty .45 Colt
I don't think I'm the only one who has a lot of blowback with .45 Colt cartridges. This leads to some mucked up receiver parts, especially with black powder. I was reading something a few weeks ago that jogged my memory about the cartridge and its original configuration. When I first started handloading it in the late '70's, the dies I had were a standard (not carbide) RCBS set. The Speer reloading manual I used stated that the .45 Colt was originally designed for .454 bullets, not the modern .451 - .452. Older guns were built with barrels for this bullet diameter so, in order to adapt the cartridge to use .451 - .452 bullets in newer guns with tighter barrels, the sizing dies were made to reduce about 1/4" of the case back from the mouth to hold the smaller bullets while leaving the rest of the case at the older chamber dimension. this resulted in a case sized to look like a .44-40, only not as pronounced. I dug out my old dies, took out the de-capper, and looked thru it. Sure enough, just as I now remembered, the inside of the die was visibly smaller at the case mouth end.
I used this information on loading my last batch of ammo. Not wanting to lube cases, I "neck sized" my .45 Colt (and .45 Scofield) cases about 1/2" back from the mouth using a carbide sizer die, then loaded as usual. The newly manufactured guns are still chambered for the old dimension cartridge, so they chambered with no problem in .45 Colt chambers. However, the "neck sized" cases are difficult to chamber in a .460 S&W Mag chamber, which is apparently bored with only the .451 - .452 bullet in mind.
After firing the LSTR match last Saturday, the innards of both the rifles I fired were dang near spotless. This treatment seems to have resulted in cleaner shooting .45 Colt rifles.
The revolvers still seemed to get just as dirty as before. I think this is because the chamber throats are still manufactured for .454 diameter bullets (I measured them) allowing gas to escape while the bullets are finding their way to the forcing cone of the .452 barrel. When I started firing .45 Colt in the late 70's the factory ammo available had .454 bullets that were soft and hollow based so they would fill the .454 throats, then swage down into the .452 barrel of a modern Blackhawk. These were not high pressure loads. More work continues for the revolver blowback.
I rambled on a bot about this but if anyone else has any insights, I'd be happy to hear them.