My first Oly was purchased about '88 or so, a Service Match w/ 20" heavy bbl. A year or two later I bought an Oly carbine, 16" heavy barrel. I have fired thousands of rounds through them, M193 and M855 ammo, with no problems. The brass shows NO signs of overpressure, and I have not had any chambering or extraction problems.
I have an Oly Ultramatch (freefloated 1" bull barrel, flattop) purchased about '96. I have fired 400-500 rnds of M855 through it, again, without problem.
It is just a non-issue.
I would like to refer you to the Armalite site, www.armalite.com, and on the left click to go to the Tech Notes. There you should read Tech Note 45 dealing with this issue in Armalite rifles, but I believe it is applicable to Oly's, too.
The SAAMI warning was more concerned with firing NATO spec ammo in other (non military) rifle types that were not designed for the higher pressure of the NATO cartridges. But the AR15/M16 type barrels ARE suitable for these higher pressure rounds.
Personally, I would be more concerned with firing the newer heavy, long 77-80gr projectiles that might be seated for a longer than normal OAL.