Marlin Cowboy Carbine 45 Colt

[High Desert Hunter]

Some interesting findings recently in regards to the chamber. It has a lot more taper than the pistol, which on my Rugers are pretty much .481 according to my pin gauges, the Freedom Arms Model 83 in 454 is .480. The chamber on the Marlin goes from .485 to .482 just behind the rifling. Rifle is more accurate than I am, may wear out brass a little quicker, but since I don't really shoot any loads that exceed 23K PSI, I'm not concerned. I image it is cut thusly for ease of chambering, and I see it loos like the maximum SAAMI specification for a 45 Colt chamber is .486 just ahead of the rim. Just found it to be an OCD piece of information.

Dave

[Scott Tschirhart]

I’ve definitely noticed that my chamber is a bit large. However, brass is just a gasket and I wear it out all the time. Just the cost of doing business.

[samsi]

I recall seeing an original chamber drawing for the .45 and it was pretty heavily tapered, although most manufacturers have tightened that up to one degree or another. It was a miltary/combat cartridge of the BP era after all, so the generous clearances were a bigger consideration than brass life.

Dave Scovill (who probably knows as much about the Colt cartridge as anyone living) once wrote an interesting column about the evolving dimensions along with RCBS' redesign of their Colt dies back around Y2K.

[High Desert Hunter]

Yes I imagine as pistol chambers fouled, having that bit of taper likely ensured you wouldn't be left defenseless in the middle of a heated exchange. I've not paid attention to the Chamber on my Ruger/Marlin 44 Magnum, but being a relatively modern cartridge, I don't imagine it has different dimensions from the pistol chambers. Plus as Scott says, the brass is a gasket, and they wear out, cost of doing business.

Dave