I have on numerous occasions watched people try and turn their AR15 rifles into sniper rifles and long range shooting rifles. The AR15 has become so modified that it’s really hard to say what it’s limitations are because their are many things that it can do if modified. I remember when the M1A ruled competitions, but now it’s really hard to find them anymore. There have been many long range shooting modifications that have made the AR15 a 1000yd rifle. One thing the AR15 is really known for doing well is being accurate. I jumped on that bandwagon a few years ago and enjoy the ones that I have. One thing that the AR15 in .223 is also known for is lack of penetration on hard targets. With the invasion of Iraq, there have been numerous stories of guys not being able to shoot through concrete walls to get a BG that was just about a foot on the other side. The AR15 with M855 or SS109 can penetrate steel at reasonable ranges, but when it comes to taking 300yd shots at hard walls, it is out of gas.
Considering what the M855 round can do as far as penetration, it’s no weakling when it comes to punching through targets, but that energy gets to be useless on anything other than flak jacket type armor. The M1A or the .308 for that matter is an over kill at close ranges under 200yds and it’s going to do much more than what an AR15 or M16 can do, but when you get out to 300yds + good rifles scopes, accurate rifles and a .308 are going to hit targets harder, punch through targets harder and save the guys carrying the M4 rifles a lot of ammo and get the job done. Mounting optics and finding really good and fast bullet compensator on the glass shouldn’t slow you down and will help you get fast target acquisition at medium ranges.