AR15 Service Rifle Heavy bbl definition
 

Rule 4.1.1c for M16/AR15-Type Service Rifle states:

No full-length heavy barrels are permitted. No portion of the barrel forward of the rearward location of the gas block or front sight tenon shall have a diameter exceeding .750”.

Does this mean a heavy barrel is defined by the latter sentence or is there some other definition of a "full-length heavy barrel"?

I have a Del Ton Alpha 320H I'd like to use

Profile is probably fine, but the Del-ton also probably 1:9 twist, you will want 1:8 or faster for 75+ grain bullets.
Mike B

K. Thanks.
Probably just run what I brung till I know if I can hit the target or not. ; )

Unless the barrel is thicker than .750" from the gas block to muzzle, you are good to go. That includes "under" the gas block.
So if the 320H, is thicker than 3/4" …….. no you can't shoot it.
Good luck!

It's .750 at the block, .730 till the flash hider so... yup, it looks like I can play.

Thanks!!