Have fun tomorrow.
I bought a LM8 (16" CL) a couple weeks ago but have only shot surplus fodder and some Privi "match" ammo through mine. I'm waiting to get 100 rounds down the barrel before I waste any actual match or reloaded ammo.
Fodder used: Privi 168gr. "Match", Winchester fmj nato, Radway Green fmj nato.
So far Winchester Nato shoots the worst at 3", with a LOT of vertical stringing. Radway Green shot a little better, around 2.5". The privi "Match" which uses a 168 gr SMK, shoots consistently around 1-1.5", but I would hardly consider it match as the SD is over 50 fps.
One upgrade I would recommend right away is a Geissele SD-E or SSA-E trigger. The LMT stock trigger is ok, but the SD-E is just amazing. I would also ditch the SOPMOD stock (sell it for $125) and buy an ACS or similar locking stock. The SOPMOD is horrendous for prone shooting with a rear bag.