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The reason you have to be careful hot rodding anything in the Marlin lever actions is simple: You don’t have enough steel surrounding the chamber to support that kind of pressure.
Contrary to common internet wisdom, the receiver has nothing to do with containing radial pressure and is responsible for arresting bolt thrust ONLY.
The bolt thrust per cartridge varies, but one thing is certain: it’s a dam sight less than radial pressure on the barrel across the board.
I can tell you with absolute cheerful certainty that the receiver of the Marlin 336 can easily handle anything the 308 or 358 can dish out.
BUT BUT BUT BUT BUT…………
The barrel CANNOT.
Understanding the strength of the barrel means taking into account the things you cannot see, and understanding how metal fatigues and fails.
The first, and most important thing to understand is that regardless of the size of the barrel you can see, the barrel is only as strong as it’s weakest point, and the threads are the smallest diameter located over the chamber of the gun which is where the lions share of the pressure takes place. Barrels are tapered because once you get 4″ away from the chamber, pressure begins to bleed off quickly (as anyone can see evidenced on Larry Gibson’s pressure traces). The fact is, that every inch the bullet travels effectively increases your expansion chamber. However, the first 3-4″ of the barrel are going to take the full pressure of the cartridge and there is no escaping that.
Knowing that, the minor thread diameter of the Marlin 336 is one of the smallest (if not THE smallest) tenon in production today. It’s perfectly suited to handling the pressure of a +p 30-30 cartridge, but if you throw in a larger cartridge, the wall gets thinner, and the pressure goes up because of what that cartridge is and how it is loaded. You could get away with it if you kept the loads tame, but all it takes is one poor sucker who does not understand what I wrote above (and very few do) and you’ve got yourself a dangerous situation.
You have to think about it like a revolver cylinder wall. It can only take so much pressure, and that cylinder gap helps a lot with an added safety margin which you do not have in a rifle.
I’m sure the 35 Remington, the 308 ME and the 338 ME and 45-70 make Marlin really really nervous, and I’m sure that what I am talking about above is one of the reasons they have let the Marlin Express line quietly die of natural causes. I’m sure it helped them float for another year or two under the JM stamp, but make no mistake, those cartridges are on the ragged edge, which is why it’s hard to get them. The 45-70 is a bit of a goofball, but they have the advantage of an big barrel to let the pressure off quickly on that cartridge. Even still, the 1895 will not tolerate much of an over load, and I’ve seen dozens of them cut in half by reloading mistakes. Compared to a bolt action, you can knock the Marlin and Henry lever actions over with a feather.
The next strongest is the 1886 pattern rifles, then the 1895 Winchester rifles (which hide a barrel tenon nearly as large as a Ruger #1!!!)
The point is, I highly recommend you take care not to overload the 336 or 1895 rifles in any way. Published book loads are fine, even up to maximum, but going over maximum is a fruitless venture that may put you in dangerous territory pressure wise.