OK fellers!!!
First, the bad news...
75AMAX didn't shoot much better than the 80 AMAX. Given 30s temps and -DA values ASL today, they just don't wanna stabilize in the 1:9. 75 Amax holes were more round than the 80s, but group size was in the 2-3" range @ 100yds. On the encouraging side, speeds for a mild load was averaged 3680 fps...not too shabby...
Now...the GOOD NEWS!
The little ladder test with the 75 JLKs turned out nicely! Shots clustered into a nice little group, with perfectly round boolit holes

As i hoped, that slippery sleek, low bearing surface JLK was a better match for the 1:9 Brux.
As for ladder test details, only got thru a few shots before noticing obvious signs to STOP. Last round I shot had a slight resistance upon bolt lift, with a 'click' at the top before extraction. Upon inspecting brass, a mild ejector swipe and slight primer cratering was evident. We all know that means STOP!
But yeah...here's the fun part! Ladder test with Retumbo, in 0.5gr steps. Check out these velocity numbers from a 75 grain boolit!!!
Yep...ya read that right 3941 fps!


That, gentlemen, is some SERIOUS speed from a 27" barrel. And...at the ridiculous MV, the 75 JLK is revvin' ~315,000 RPM from the 1:9 twist. IF I'd went 1:8, it'd be in the ~355,000 RPM range

and doubtful the 75 would even make it to the target...
Soooo, I'm tickled pink now! Got some good data to extrapolate from, and on the way to finding a good load with the 75 JLK. Still, will order a box of 69 TMKs and 70 VLDs, just to see how far over 4,000 they'll go. Cuz, now I know they will...
Lots of fun work to do! But, yeah... almost 3950 from a 75 grainer??? That's whoopin' azz on my .22-243AI to the tune of 350+fps, and that .22-243AI is one BAD mama-jama...
Stay tuned for more! Should have the REDLINE's GameScout stock in hand, soon. Quick bedding job on that won't be any trouble. Then, back to load testing and dialing on a decent, consistent load to take afield. Gonna be a fun Spring, woodchucks BEWARE!!!