I was at a gun show recently and ran into an avid M1903 and A3 collector who determined that my rifle is 95% original. The only incorrect piece was the follower--which was designed for an '03, not an A3. I am excited that she is mostly original--must have been stored in a safe place during the war(s).
I had a chance to shoot her as well and the rifling is pristine. I routinely hit 10-inch gongs at 150 yards offhand. It is such a fun gun to shoot.
It is not a matter of not much meat (I am tall and skinny) more a matter of it resting on your collar bone (and brusing the crap out of it).
I have noticed a fair bit of people who shoot ARs regularly have the same type of stance, likely due to the rubber butt-plate and soft recoiling round.
One of the great things about military arms is interchangeability. You have a dozen broken rifles and from those broken rifles you can make half of them serviceable because all the parts fit the same. Any 03 part will fit Any 03 any M1 part will fit all other M1's and the same with the carbine the BAR nd to some extent the Thompson. So in my humble opinion it the part fits and functions properly it's the right part.
---------- Post added at 11:37 AM ---------- Previous post was at 11:34 AM ----------
An odd thought. I wonder if seventy years from now there will be a bunch of guys discussing if that M16 is an A1 or an A3 model and are all the parts correct.
No Offence but you need to get into the rifle it appears you are hanging off the end of the butt no wonder your shoulder was knackered, you are pretty much point loading your shoulder with the heel of the butt. There are plenty of books and vids out there for you to learn about correct technique in all aspects of shooting. Like most things it takes practice to let it become second nature, every time the trigger breaks it should be a surprise, rather than anticipating the sear to drop and fire the weapon you know your getting better when the groups start shrinking.
Now just some other advice if you are going to reload like most of us do study the books and develop loads that work in YOUR rifle not a recipe someone else's 03 likes. Avoid the types that expound knowledge but are quick to blame their gear unless it is a glaring failure like the mag dropping out etc. As that type to me just frustrates the heck begeezers outa me as when you watch them shoot their technique is just crap and when you try to assist they say they know how to shoot, fair call but you are still at the bottom of the ladder every week......! Above all treat the weapon with the respect it deserves most of the gear we shoot is 100 years old (My MkIII is a Lithgow 1916 I shoot once a year) keep loads reasonable but not heavy and clean it properly. Enjoy your fun as you seem like a pretty open person that has the same values as all of us here "Appreciation for the rifles we collect and respectful of each other."