Correct. A normal H2 buffer will work well. The A5 would be way too long.
From Spring Co
"RED Spring": EXTRA Power Buffer Spring, Best option for 16"+ 5.56 barrels with carbine length gas system platforms with standard front sight towers and H buffers, 16" + BBL gas piston guns, *some* suppressed shorties,and later generation Colt LE6920's, 9mm, 6.8 SPC, 6.5 Grendel, .458 SOCOM, 450 Bushmaster, .500 Beowulf, and assorted "Thumpers" using standard 7" depth M4 extension tubes. AR-10 Carbines (E.G. Armalite, Noveske, LMT) using deeper extension tubes and standard length carbine buffers to accommodate the longer .308 BCG also use the "RED" Spring. Please call us to discuss successful historical "recipes" for implementation of the RED spring in .308, 6.8 SPC, etc. RIFLE length extension tube platforms. Color Coded RED. NOTE: NOT for use in .308 Carbines using standard 7" M4 extension tubes and short, stubby buffers. (Use our "ORANGE Spring" below for that specific platform approach application.) NOTE: If you have a seriously overgassed .308 Carbine which has the deeper AR-10 platform receiver extension tube running an H3 buffer firing 175 Gr. Projectiles and / or suppressed, many shooters have experienced success using the "ORANGE" spring, as it is still heavier than a "RED" spring in that application.
Also, it isn't the stubby one as mentioned above either. I saw a LE Agency butcher some OBR with LW barrels and say they were unreliable once. They put those damn stubby buffers and flat wire springs from LWRC Reapers with UBR stocks in the OBR like morons. Not all AR10 are the same
Anyway, I fixed the ones I could get my hands on. Pissed me off to be honest. It changed how the LEO viewed the OBRs because somebody didn't know what they were doing.