From Hatcher's
The Book of the Garand are the following loads, in chronological order spanning the end of WWI to the end of WWII:
.30 M1906 - Flat based, 150 grain, cupro-nickel jacketed, 2,700 fps, maximum range 3,400 yards, at 50,000 PSI.
.30 M1 - Boat tailed, 174.5 grain, gilding metal jacketed, 2,647 fps, maximum range 5,500 yards, at 48,000 PSI.
.30 M2 - Flat based, 152 grain, gilding metal jacketed, 2,805 fps, maximum range 3,500 yards, at 50,000 PSI.
.30 AP - Flat based, 168.5 grain, gilding metal jacketed, 2,775 fps, maximum range 3,500 yards, at 50,000 PSI.
According to Hatcher, the M1906 and M1 loadings were both designed for the Springfield; the M1 was developed in response to the effects of plunging fire witnessed during WWI. When the M1 ammunition was supplied to National Guard units, many of them found that it shot too far to be safely used on their ranges and they requested additional M1906 to be manufactured for their use. This resulted in the M2, which is merely a product-improved M1906 loading. The AP loading came into use during WWII and obsoleted the M2 load by 1944; evidently it worked just as well as the other stuff on flesh and blood but was better at penetrating cover and vehicles.
Contrary to some claims, Hatcher maintains that the M1 Garand could not only handle the M1 load, but that it was actually developed primarily with that load and could almost be considered to be optimized for it; he further goes on to mention that Garand himself was worried that the rifle wouldn't function correctly with the less powerful M2 loading. The development timeline of the rifle, along with that of the various loadings, seems to support his claims. It's a testament to the rifle's design that it actually handled all of the loadings satisfactorily without modification.
Unfortunately, Hatcher does not mention the sizes of the powder charges. (He actually does mention a few here and there but they're scattered through the book and I'm not going to track them down.) He does discuss how improvements to the powder itself figured into each new load.
It's generally accepted that while the action itself is pretty darned strong, the op rod can be damaged by unusual pressure curves. There are loads that are recommended and loads that aren't. In general, staying close to what the gummint was loading cannot be considered to be a bad idea, but other things can be safely handled by the rifle. Some of Hatcher's testing makes my antics look positively benign. I suppose that weird or excessively violent operation -- either from very high pressures or excessive recoil -- could eventually cause a failure at the rear of the receiver from bolt hammering. Hatcher noted that this was observed early on with rifle-launched grenades and was fixed by modifying the gas system and drawing out the rear of the receiver to a lower hardness and higher toughness. While my experience with the M1 is limited, my experience with the M14 spans some years and many shots fired and the two systems are similar; even with the infamous "extended range" grenade launching cartridges (essentially 150% overloads) that we manufactured for enhanced linethrowing performance, I don't recall ever witnessing a bolt or receiver failure, although the stocks did occasionally break.
(It didn't seem to hurt the op rods either, but you know what they say...)
When (not if) I get my Garand and start handloading for it, I intend to stick with proven powders and bullet weights, using published data and the chrony to duplicate government loadings as closely as possible. I'm not particularly interested in experimentation in this case; the government spent half a century experimenting with that cartridge and I have no wish to duplicate their work. Any of the loads that they settled on are probably good enough.
Suffice it to say, while Hatcher's books are pretty dry they make for
excellent reading if serious study is the goal. Think of them as textbooks for historically-minded gunnies.
With regards to the Mosin-Nagant, the resemblance to the Mauser is only cosmetic. The magazine and bolt designs are considerably different. The magazine was necessary for the M1891 cartridge; the reason for the bolt is a bit more difficult to explain, but Hogg felt that their bolt may have simply been a way to avoid paying royalties to Mauser like everyone else was doing.
