Okay..I guess...to stop the "arms race" we, ( Refs in my world), simply a) used cops and corps, just like the real world or b) if they were sufficiently clever, they had their arms race. Graduating to Big Boys World. Nothing wrong with that.
You rarely - need- the big guns, although I'm not sure what you mean by "big guns". Rifles? SMGs? V Hvy Pistols? Anyway, the reason you use them is to even the odds and/or make a hard job easier. Why they were invented. Anyway, Cpunk is such that killing a PC or NPC is pretty easy. .22 will do it, poison, blackmail...
My point was more that assuring PCs of any NPC action out-of-game is kind of metagaming and, um, weird. Don't your players feel cushioned by some agreement with you then? Safe?
Oh, wait. Are you being clever? Do you later betray them evilly? Because if so, KUDOS, sir.