Would it be worth the cost to use match ammo
in a AR with a 16" barrel?
Would it be worth it to use something outher
than 55 grain bullets?

UUHH for what? i mean what's your motive? what is your twist? gonna shoot paper or other?

I recall a posting awhile back in which someone was shooting 1/3 to 1/2" groups with an AR10T Carbine using three different handloads.  

Will be shooting 3gun/tactical rifle targets
out to 200yds.. Paper of course and yotes.
Twist unknown! I just looked on the barrel and there are no markings. The rifle is an
ArmaLite M15A4c.

hangfire, it is helpfull to know the twist rate of yor rfle. fortunatly, it is not too hard to check. Take your cleaning rod make a line along the length make a mark in line at the muzzle and run the rod in until it makes one revolution mark that point on the rod and measure the length--there you have it. If the rifle is in decent shape and the rate of twist is 1in 8 or more (probably 1in9)than match 55 is hard to beat at the ranges you mentioned. for hunting you may want to go with a more frangible bullet for knock down. in three gun keep in mind the smaller the bullet the less the recoil, the less sight picture disturbance and the faster you reaquire your target. hope that helps.

Peregrine,
Thankyou.

52gr. Match works very well.

depens, for what? mine loves federal 69 gold medal match & everything else except Q3131