Go, go plan PI!
On the subject of rifles:
Why don't we just make a M1 Garand?
If you want a gun with magazines we could make a T20E2:
https://en.wikipedia.org/wiki/M1_Garand#T20E2
Which is just a Garand that can use BAR magazines.
That would be fine, but I want to reiterate my call for a more modern caliber. The Garand used big heavy rounds that are not much better than what we have already (OK, a little better).
Trust me, we don't want bolt action. They are quickly becoming obsolete in our time period. They will continue to be used for a long time yet, mainly due to production issues (to many other things to build, like tanks) and weird ideas like "the soldiers will use too much ammo".
I have a K98 (one of the the best bolt action military rifle ever made), and once had a
Schmidt-Rubin (another fine rifle that I only sold because the ammo was way to expensive). The K98 was a very well made example of the type, almost new (issued to an SS trooper straight from the concentration camp where it was made, then he then promptly got his ass shot and his rifle shipped to the states as a souvenir (it has some really interesting stamps on the receiver/barrel)), even so it was far slower to fire and reload than most of my other rifles. The Schmidt-Rubin (which handily fits our time period) was faster to fire, but every shot still required you to work the bolt. On the Schmidt-Rubin unlocking the bolt quickly required a tricky little jerk (quick and smooth once mastered, but likely to move the rifle between shots), whereas on the K98 you could throw the bolt with a couple of fingers in one glass smooth movement (slower, but easier).
Despite both rifles being excellent examples of their kind, if I was going to war with one of the rifles I have owned over the years I would choose one of my SKSs (all of which were cheap, inferior examples of their kind). Why? Well for one thing the ammo for the SKS is a lot lighter/smaller, for another it can fire much faster if needed, and it loads just as quickly (all three rifles mentioned here had fixed mags).
I say we go with the best semi-auto we can design (and don't think we can't design one either, look at the
Mondragón rifle, if Mexico could do it in 1904, we can now). The rifle we design now will have to last use the whole war.