I thought this would be a simple little thread. Didn�t know there would �smiley faces.�
When we began a serious comparison of the various lever action rifle cartridges of approximately the same case capacity or velocity potential - .30-30AI, .307, .375, .356 and .444 - we found the difference between the .38-55 and the .375 Winchester to be interesting and a little confusing. We knew why Winchester had to make a different cartridge � all of the older (and perhaps weaker) rifles standing in closets. Winchester knew full well the .375 cartridge was going to end up in a .38-55 rifle sooner or later. Winchester could not make the .375 cartridge longer to prevent its chambering in the .38-55 and still be able to work it through the Model 94 action. By making the cartridge case shorter and reducing the bore diameter Winchester could be reasonably certain that firing a .375 Winchester cartridge in a .38-55 rifle would not result in a �serious� high pressure situation.
We fired the .375 Winchester in the .38-55 Encore as an experiment while looking at PRE dimensions for the various cartridges. Our very limited results indicate the 200-grain .375 Winchester factory loads PRE slightly exceeded the PRE of .38-55 handloads (using new, unfired brass and .375� diameter Sierra 200 grain bullets) with maximum published loads. The .375 Winchester PRE from cases fired in the .38-55 chamber were less than those of the same cartridges fired in the Winchester Model 94 Big Bore rifle.
This was nothing more than a quick look as you well know. The Encore is throated for bullets of .3785� to .379� diameter. The .375� diameter Sierras are a pretty loose fit in the throat. I don�t know how the bullets compare to one another for bearing surface.
Current Marlin .38-55 Cowboy rifles have a bore and throat suited for .379� bullets. .375 Winchester ammunition using the .375� diameter bullets are a loose fit in the throat and the bullet will let quite a bit of gas escape past the bullet as it travels down the bore. I am not advocating using .375 Winchester ammunition in .38-55 rifles and I don�t think Ken Waters intended that either. I am just saying that through some pretty interesting forethought on the part of Winchester doing so will probably not have catastrophic consequences. Someone from Winchester probably spent quite a bit of time figuring this out in an effort to produce a powerful new cartridge that would not act as a hand grenade when it was inadvertently fired in a .38-55 rifle.
While not part of the original question, I believe shooting a .375 Winchester cartridge in a modern .38-55 Cowboy rifle is a lot safer than the practice of using .38-55 brass to handload .375 Winchester cartridges in the hope the slightly greater case capacity will give higher velocity.
Due to comments in threads I have seen on other Forums I think DaveKing has asked a reasonable question.
