........ Interesting someone actually used the correct term for the gun known in the game as a "Assault Rifle." XD
Well note that is IS using a 7.62 bullet (I'm assuming though it's like the Pulse rifle, caseless..... I'll have to check that out though actually. xD ) and back when the FN FAL and M14 were tested at fully automatic fire, the caliber had a notorious kick that often threw the lead off target, hence why all the Battle Rifles like them and the G3 were strictly used as Semi-Automatic weapons.
My suggestion when using this weapon is to try aiming for the feet and legs of the Xenomorph so when the recoil kicks in, it can cause the ammunition to strike the alien in the face. I have killed Aliens in one three round burst at times, but usually I can get them in two or three depending on their perks. = )
Though in my opinion, the five shot burst is completely pointless to have. Mostly because it eats your magazine very fast and your stuck with a 30 round magazine unlike the Pulse Rifle boys. = P
It's actually my favorite gun to use in the game, I have very few problems with it. The flamethrower is also nothing to scoff at either. I love going all R.J. MacReady on the Xenomorph players. xD