What cans are we using on SBRs and AR pistols?

[WillBrink]

Your only selling point is defeating body armor,

That's a pretty big selling point to some, can't say that's a major issue I'd worry about.

and ammo availability, but now youre pigeon-holeing yourself to a couple specific loads?

If the rec is defeating BA, limits choices. If not, a wide range of choices from all major manufacturers exist now that will do 2200-2400+ fps (depending on weight) and offer excellent terminal ballistics exceeding that of any pistol in typical duty loads, pistol caliber carbine, or PDW, by a margin, in SD/HD distances and then some.

I tend to view it a PDW that's using a rifle bullet, and an effective one at that, some can't let go of the rifle aspect, and continue to compare to rifle. Compared to a 10" you are giving up something to be sure, not nearly as much as some seem think for the role of HD/SD/PDW by the easy to supply numbers.

For example, the Federal MK 318 Mod 0 (SOST) 62g is barrier blind design, does 2200 fps from a 7.5 inch barrel and performed very well in jello testing by wide margin to any pistol in typical duty loads, pistol caliber carbine, or PDW. While that's not the easiest load to find, again, major manufacturers offer various similar. Anyone claiming "just use a pistol caliber carbine" at this point has no credibility here.

There is an argument to be made for longer barrel ARs to be sure, but it's also an apples to oranges thing to me. Conclusion:

7.5" (or dare I even say, shorter!?), is vastly superior to any any pistol in typical duty loads, pistol caliber carbine, or PDW.

It is inferior to longer barrels depending on the role it's intended for, but not as inferior as some seem to believe.

300BLK would be more optimal all around, but 5.56 is much less $ to run (and that's no small thing these days!), far more available, and more then adequate terminal ballistics with the right loads, which are now common. No, it's not the most efficient use the 5.56