It is listed in the rules for service rifle.
http://www.odcmp.com/Competitions/Rulebook.pdf
Page 22.
you have 3 rifles to choose from:
M1 Rifle .30 Cal
M14
AR15/M16
If you shoot NRA high power, the AR10 format isn't even allowed.
http://www.nrahq.org/compete/highpower.asp
Rifle: Rifles to be used in High Power Rifle competition must be equipped with metallic sights (Some long range, 1000-yard matches allow the use of "any sights"), should be capable of holding at least 5 rounds of ammunition and should be adapted to rapid reloading. Tournament programs often group competitions into two divisions, Service Rifle and Match Rifle. The rifles currently defined as "Service Rifles" include the M1, M14, M16 and their commercial equivalents. Winchester and Remington have made their Model 70 and Model 40X rifles in "match" versions and custom gunsmiths have made up match rifles on many military and commercial actions. 1903 and 1903-A3 Springfield, 1917 Enfields and pre-war Winchester Model 70 sporters in .30-06 are all equipped with clip slots for rapid reloading. The most suitable rear sights are aperture or "peep" with reliable, repeatable 1/2 minute (or finer) adjustments. Front sights should be of either the post or aperture type.
You would be able to use the AR10 in the F Class matches though.
http://usfclass.com/rules.aspx
But if you are going to shoot F-Class, plan on competing against a bunch of bolt guns that will walk all over that auto-stuffer.
I have a scope mount for my M14 if I ever want to use it. I choose to leave it iron sights though as it's set up currently for service rifle competition.
