The only one I've tried is the 139g .284 in a 7mm Remington Mag. I eventually found a load that would go sub-MOA for 3 shots, although it was much more work to find than the 150g Barnes TTSX. That was the easiest load work up I've ever done with that rifle. 0.5-0.75" 3 shot groups.
The GMX did seem to be a bit sensitive to seating depth. When first testing the bullet, after finding a good charge weight I tried various seating depths. My load work-up was initially done at 3.320", but I decided to test various other seating depths:
3.360" COAL -> 3.079" 3-shot group
3.330" COAL -> 1.306" 3-shot group
3.300" COAL -> 1.234" 3-shot group
3.280" COAL -> 1.318" 3-shot group (don't ask my why this wasn't tested at 3.270", it was 7 years ago.
)
And later:
3.290" COAL -> 1.618" 3-shot group (not sure what happened here...)
After switching powders, later testing with more shots showed that the GMX could reliably run 1 MOA to 1.25 MOA. I won't complain about that performance for large game (in this case, Elk).
It's my backup hunting load if for some reason I run-out/misplace the 150g Barnes TTSX.
