Originally Posted by GT98SVO
What is A4, A3, A2 etc.?
What is B.U.I.S.?
Anyone shoot varmint with these?
What your favorite for a long range plinker/varmint brand?
The numbers (A2, A3, A4) are the generations.
A1 = fixed carry handle, teardrop forward assist, triangle handguard, (semi or full auto for M16)
A2 = adjustable rear sight, 5/8" longer stock, heavier barrel, round handguard, (semi or 3rd burst for M16)
A3 = same as A2 but with the A1 fire control group
A4 = Flattop reciever (removable carry handle), (semi or 3rd burst for M16)
There's some goof info on this here: http://dunlaparms.com/faqs/What%20is...20A3,%20A4.pdf
BUIS = back up iron sight
Yes, you can definitely varmint hunt with them and its damn fun! (good optics definitely help!)
As far as favorite for varmint... I don't have one. I've done just fine with a "stock" 20" Armalite and a decent scope, but there are some guys who will tell you that you need a 24" bull barrel, $2000 optics, etc.