Yep, the 336 was also chambered in the late, great .356 WCF.
If I recall correct, the .375 predated the .356/.307, an like W. says, the 307 was announced an never built.
In any case, the 356 was indeed a high pressure number.
My point about heat treating is that certain parts may have had a lil extra dose, or may not, I've asked this question of others more in the know than me.
Marlin in those days apparantly did not do a ruger, they did a kimber-their parts were chosen for their gun, an rode along together till done-thus part no.s alone won tell the whole story.
Maybe you know more n me, an maybe you can put it to rest?
Anywho, were lucky that there still are .375s/.356s out there-they really are great cartridges.
