They're working on that, however, what are you going to do if/when they manage to open a major portal somewhere like NYC, or even the increasing likelyhood of individual attacks in places like malls.
Fair enough. Again I'd go for the 12 gauge slug gun idea for this.
The portal has only been successfully opened once so far, and into the closest equivalent of indignant friendly forces available(some escaped dead souls).
Well, keep some nukes wherever you're doing portal research. If you succeed again, do a quick peek and if you're anywhere near the baddies, send 'em through. If you're near the escaped souls ... maybe you send it through anyway. Those folks are dead already and I'd be a little concerned about the billions and billions of dead hell has stored up coming back to us.
Hell's teaming with friendlies held in the equivalent of the biggest, nastiest POW camp ever. With even the forces being diverted right now, we'll likely be able to start freeing souls because the guards are the equivalent of reserves - who are now being called up, leaving gaps in coverage.
Hrm. So what's the goal? We free these souls and then let the dead souls take over hell? Or are we going to bring them back to our world? What happens to a soul that dies in hell? Do they get to go back around and try again? Do they die forever? What about demons? Do demons respawn in hell when they're killed?
The demons are generally quite fast on foot, wouldn't we want the extra range rifles give over shotguns? Would 000 buck even penetrate enough at anything longer than 'point blank' ?
If you're targeting small groups or individual soldiers, most folks aren't going to be able to hit fast-movers at ranges beyond point-blank anyhow, but I agree with the problems with buck, hence my suggestion to use slugs. I like the idea to use cast iron slugs. Probably not as much force as lead, but cheaper to manufacture and will do enough damage to be worthwhile, I'd think.
You've got tons of benefits. There are tens of millions of 12 gauge shotguns available right now in the US, so lots of folks could use the weapons they already have. It should be effective enough (unless demons are armored) and is relatively cheap to manufacture the guns and ammo (compared to, say, .50BMG or dangerous game calibers). Plus, considering the amount of shooting you're planning on doing in urban areas, it might be a good idea to go with the limited range of the slugs.
Of course, there are downsides (recoil, amount of ammunition one person can carry, size, etc) but I think given the problems at hand and the requirements they're a good compromise. The concern is getting something out there ASAP, correct? No reason you can't augment the slug guns with other toys as they become available.
Oh yeah, and I think RPGs would be a good investment too.