If they are calling up 63 year old vets then there are some issues - and having to provide your own firearm isn't unlikely. Considering there are over 25 million prior service and there are just enough guns to go around in the military, you be the judge.
Ammo compatibility, either 9mm or 5.56?
Range goes to 5.56.
magazine capacity goes to 5.56.
Lethality at 125 meters, 5.56.
Point blank holdover to 250m, 5.56.
Parts availability, AR15 over M9.
Accessories, AR15.
A 10.5" AR15 PISTOL with iron sights and sling, ten 30 magazines, MK262 OTM ammo. Why would I want a dinky 1911 with hardball that couldn't penetrate a 50 year old helmet even then? Or combat Tupperware that can't keep up mag for mag against opposing fire at longer ranges?
War isn't about it being a fair fight, it's about superior firepower and not giving the other guy an even break.
I'd just bring my deer hunting pistol.