What are the pros and cons of running a h2 or h3 buffer? Have a h2 in my 300bo and a standard buffer in 5.56. Think I should swap? Just get a different one for 5.56?
A heavier buffer will retard the cycle rate of your bcg. I would try running a standard carbine buffer in the 300 blk. Of course, if they're both running fine, there is nothing to fix.
A heavier buffer is helpful if you're experiencing violent ejection of the casings. In a 9mm or especially a 45 ACP AR where blowback is the design, a heavier buffer is recommended. But as S4F said, if your 300 BO ain't broke, no need to fix it.
As mentioned, the buffer (and all of the reciprocating mass, bolt & carrier included), affects cyclic rate/bolt speed; which in turn affects ejection. If your gun has reliable consistent ejection but not violent, leave it. I have a standard buffer (i think) in my .300blk, it runs great so far on both subs and supers, so I won't change it.