This is at 75 yds with a 27X scope, so about a 2" 100 yd 10 shot group is the very best I achieved out of all the bullets tried ...the 300 Sierra MK was about the same but with AA 1680, but higher S/D at 75 yds. So IMR 4198 300 gr Berger was the winner. I do not have an expansion test medium, other than simple water jugs...but I doubt any of these expand, as is. The 225 gr tipped GMX copper bullets tried had double the group size at 50 yds and 5 shots... velocity a bit too high into 1150 fps ave the high velocity was also disappointing with about 1900 fps. According to Hornady the minimum muzzle velocity is 2500 fps for reliable expansion...so they won't work even at maximum effort from the 8.6 in a 16" barrel...according to the manufacturer.What kind of accuracy were you getting with that load? Do you have a method for testing the subsonic expanding projectiles? Interested in how the slower twist is going to compare. I’m going to wait to order a Mos-Tek 8.6 barrel if it works out well with subsonic expanding projectiles.
"The bullet" would be the Hornady FTX Marlin express 200 gr 338 at maximum effort (super sonic) in the 8.6 blackout it has a minimum expansion velocity of 1800 fps...But Not in a 3 twist! The 3 twist limits the killing power as it confines bullets to low nonexpanding velocities...subs are fun, but I want to be able to shoot the supers too...where the real performance is at for hunting.