The 55's in my 1/8 18" barrel don't group great, I can only hold around 1.5" at 100yd
But those are generic FMJBT 55gr bullets... at around 3000fps... For 3 gun... I have no problem with that.
The 62gr bullet's, that are pulled that I load.. with the same powder load as the 55gr, I have not chrono'd, but shoot just fine, and will hold under 1" at 100yd.
I would guess a heavier bullet would do even better in my gun.
I run 2 loads... 100yd and under load with 55gr... and my 62 for the longer range stuff, where accuracy counts more.
I'm sure this will evolve over the course of this season.