In the most recent issue of Rifle magazine, Dave Scovill has made some comments in his monthly column. Those comments are directed at some who Mr. Scovill feels might be expecting too much of the Marlin rifles. I believe, from reading the article, that he feels that way based on questions on conversions that he receives. He also posts a chart showing common lever gun rounds and the SAAMI pressure standards for those rounds.
This has caused no end of comments in a topic on the Leverguns.com forum. Many, including yours truly, have weighed in with words of wisdom regarding Mr. Scovill's article. Some are actually wise, some aren't. I feel as though I've been invited to a wrestling match with a pig. You know, you both get dirty but the pig LOVES it. That's what has made me think about this subject of cartridge suitability for the Marlins, most particularly the M336. It has also made me rethink my work with the .38-55.
I'll start by saying I'm not going to disappoint any readers of this blog or people who think that the .38-55 can be safely loaded to 42,000 psi same as the .30-30. I will continue to do so. In actions which will accomodate the 7-30 Waters (45K psi) and the .30-30 or .32 Special (42K psi) I think it is logical, reasonable and safe to load the .38-55 to 42K psi and I think that means that my load of 32 gr. of RL-7 under the 255 gr. Barnes Original or Stone Fence bullet is safe and within these standards.
However, I do not believe a couple of things that some do seem to believe or know. First, case shape does affect breach thrust in actions where the case head does not contact a standing breach. This includes the leverguns. In the leverguns, the bolt acts as a piston and pushes against other moving parts such as the locking lugs/bolts and over the distance of the length of the bolt can have a greater affect on the action.
The second is that the Contender, is a different animal and in that "case", where the case head contacts the standing breach (a part of the frame, not a moving part), the surface area of the case head and how much pressure is actually transfered to the breach is what is important.
This has been debated ad naseum over the years but I'm going to take a stand that I will follow in how I handle my own guns and reloading. I'm not going to rechamber the Marlin M336 for cartridges which produce in excess of 45K psi.