Strange, can't say I've ever heard of using an ar15 buffer before. What made you use that one? Spikes recommendation?
OEM Armalite uses a "Vltor length" carbine buffer tube ( many places sell buffer tubes that length ) , the added 3/4" length of the buffer tube allows the use a AR15 3.25" carbine buffer with a .308 Large Frame BCG.
Aero Precision uses a AR15 carbine length buffer tube... ( as well as numerous of manufacturers ) ... you must use a 2.5" 308 buffer in it. KAK sells a heavy weight 2.5" 308 Carbine buffer.
Your rifle will benefit from a heavier buffer weight and heavier recoil spring , putting in heavier parts will make your BCG unlock slower by milliseconds... and allow extraction at a lower camber pressure.... ( far easier on the brass ) BUT...
Ultimately, controlling the volume of gas will result in ( IMHO ) the best way to control your "abrupt" cyclic speed. The heavier buffer and recoil spring "helps" but the BCG ( regardless of BCG weight and reciprocating mass.. which you'd still like fairly light ) is still "controlled" by the volume of gas coming from the 308.
Most all I have seen ( 308 / 6.5CM ) AR's have been "over gassed" ( not a perfect choice of words, but ) ... a lot of times to the point of causing function issues.
Slowing the cyclic speed... with heavier buffers , recoil springs and an Adj. GB WILL change the "perceived" recoil impulse.
I say "perceived" because all your spare parts are really doing .. is spreading out the time for the extraction and unlocking of the bolt... and that will make that happen at a lower chamber pressure... and those few milliseconds slower is all it takes.
As mentioned earlier... all those parts have made my Large Frames shoot very, very softly I have no problem sitting at the bench shooting them ALL day.
I still suggest a Adj. GB.. seriously it is an amazing difference.
So much better, I run it on all my gas system lengths, stock setups, 308 caliber / 6.5CM ,and various barrel / barrel manufacturers and lengths.... basically EVERY Large Frame AR gets one.
And buy that sissy pad I linked to for your stock... I have one on every Magpul carbine stock... 9x19 PCC, .223 / 5.56, and Large Frame AR