I havent cut grooves into the lower, just the windowed mag got me to 2.375” as max in the lower. Seating long, got 2697fps average with the 87gr vmax in the 16” 6x45. Jam is 2.370” with that bullet in my chamber, and I pushed my load back to 2.355” coal aka 1.885” cbto. I don’t want to worry about the tips rubbing and ease the chance of setback. I think I could gain another 50 fps with another powder, but isn’t necessary for my purposes.Cut a few grooves in my NFA lower to allow 2.400" OAL with my windowed mags. Hello, 88 ELDM! Could maybe get a little more OAL but the NFA is getting thin on material up there. I think 2.45" would punch through the lower. How does the TN Arms compare?
The upper and barrel extension will take a little massaging but should be good after that.
According to GRT, I should be able to push the 88s to 2650 with my 20" barrel, keeping things above 1800 fps at 5000' out to 675 yds. Not that I'm shooting that far on game...