>>63940188M14 doesn't quite work because it was an attempt at sticking with battle rifles when assault rifles had already proved superior. There's an M14 mindset in the XM7 though.
The Krag REALLY doesn't work because it very much was a concrete upgrade compared to the rifles in previous service, and it wasn't even half bad, rather a mix of the design of the rifle and the less than perfect metallurgy (the same problem haunting very early Springfields, subpar heat treating), doomed it when the army decided that it wanted a Mauser like everyone else.
When they were eventually surplused, they became quite beloved as hunting rifles in civilian life.
>>63945032Reising doesn't work either, it was brought in as a stopgap to outfit the Marines with SOME kind of subgun, just because the Army had dibs on all the Thompsons and the Navy had no other options.
Far from perfect, but the idea was probably that it'd be better than no subgun at all.
>>63946090Hilariously, this is undone by he catastrophically loud XM7 needing a suppressor which makes it basically as long as a full length rifle anyway. MWAH MWAH.