replicating action movie results, by the book

[Varyon]

Shotguns in a cinematic campaign should do knockback - possibly double knockback, if not more. Assuming 640 lb, the terminator would have HP 17 for knockback purposes (as an Unliving object, it would actually have ST 34 or 35, and HP to match, but I think you use the HP of a Living object for purposes of knockback; at least, you should). That means a knockback threshold of 15. A close range blast from a shotgun is generally going to be 4d+4(0.25) pi++, for an average of 18. So if you have shotguns deal knockback like a crushing attack, that's 1 yard of knockback on a T800 (and just 2 yards on an HP 10 human), while if you have them deal double knockback (36, above), you're looking at 2 yards (4 yards on an HP 10 human).

In a campaign where firearms deal knockback, something firing 5.56 is generally unlikely to cause much, as it's infamous for firing a rather light bullet (indeed, its width isn't much more than a .22 LR - 0.223" - but it is markedly heavier and traveling well above the speed of a .22 LR). I could see cause for a setting switch where firearms cause knockback to have pi- do half knockback, pi do normal knockback, pi+ to +50% knockback, and pi++ do double knockback. Firearms that fling bullets that should be pi- but get upgraded to pi due to high velocity would be treated like pi- in such a setting. So, a .44 magnum firing hollowpoint rounds for 3d+2(0.5) pi++ would deal, on average, 25 damage for purposes of knockback (3 yards against an HP 10 human), while an M16 firing FMJ's for 5d pi (treated as pi- for knockback) would only deal, on average, 8.75 damage for purposes of knockback (just enough to knock an HP 10 human back 1 yard).