>>570645
This could be fun.
>service rifle
First, of, LETS STANDARDIZE THE AR-10
that size of bolt can be made small, to hold things like 6.5 memedal, which honestly isn't a bad choice, or 50 beowolf, or a host of other choices. Recognizing the importance of carrying more ammunition, while not wanting to limit ourselves to the 556, I'd say let's go with about the 6.8 SPC, 16" barrel with a 14.5" not too hard to get. DMRs get the venerated 762 real-flippin'-NATO in 20", or 6.5 creedmore / 24" if they want to be snowflakes. (actual snipers would get to be as snowflake as they like so long as they can demonstrate 1/4 MOA at 1,000 yards during yearly qualifications)
This has the side effect of making it much easier for civvies to build giant wildcats-of-the-week like 45 Raptor, or rechamber their former service rifle for 270 WSM, much cheaper/easier.
>pistol
Not having studied their usage, I shall make some random guesses. They're good for dealing with ambushes when you didn't have your service rifle already in your hands. They're also good for making officers look more decorated.
So, is there any difference between a "double stack 1911" and a "2011 style pistol" ? Because that's my choice here. Slide (barrel/ammo) would be available in two forms: 10mm (or, a re-imagining of the .45ACP, such that it's a forty-five but with modern metallurgy / pressure limits kept in mind) for most cases, particular for guard duty where you expect combatants are towel-heads or the equivalent, IE no armor. For military engagements, something small, fast and armor piercing. Bring back the 5.7 SS190, use sabots for SS109 bullets (accuracy in cases where a soldier uses his pistol are likely to be completely irrelevant) or start with the .357 SIG and build it up.
Too, the .357 SIG could actually have several loads – long, heavy hollow-base for Stoppin'Powah, and carbide or carbon -steel core zingers for AP.