CQB in this game is underdeveloped, but still quite realistic. Definitely takes practice to get good at it. Making use of flashbangs, grenades, etc. are great for getting every advantage you can get. While it's nice to avoid CQB entirely or clear from the outside before breaching (shooting through doorways, windows, using grenades, etc.), there are times were you can't give yourself these advantages before breaching (hostage rescue being a prime example, especially when it's likely the hostage will be killed soon after you're detected).
SMGs are plenty useable in CQB, just have to learn how to go for headshots. If you have a heavy body armor mod (which is an extra in HU), then not even an M14 will pierce it. So even with an M4, be ready to adjust your shot placement. As for SMG vs assault rifle, I find little benefit with the SMG other than pure style. But then again, SMG use has definitely decreased in the modern battlefield.
It would be infinitely better to just use an assault rifle or CQC rifle. There is near zero benefit of the SMG. Let's be honest, the close quarters game in this lovely old game is something you want to avoid ANYWAY. The cumbersome movement combined with the AIs never moving and their laser reaction time makes it a no-go anyway. Up to a certain range, an SMG should be way better. it should have little reticle spread and should waste people up close. Even with armor, getting filled up by an SMG would knock anyone down and likely kill them. Armor only does a little.
They are viable in the correct situations. You definitely don't want to use them in long range, that's why you got Rifles. You don't want to use them against armored targets, as against those, if it is not a headshot, the bullets will simply bounce off their armor, they'll get stunned a bit as well. I use them in CQB against any target, but the key is, going for the hit stun (By shooting them anywhere) then going for the headshot, otherwise they are not good. They get more useful in the Desert Siege and Island Thunder, where not everyone is wearing armor. Just like every weapon, it is a matter of using them in the right scenario.
This thread is mostly random
I added a small file for the Heroes Unleashed mod. The mod is large and I do not know how it works but the files included if placed in the correct folder would replace the original files so back up if you are not making changes. Only 2 files are modified and affect several kits that contain the weapons.