I think the nockturnals i use come with a few sleeves that allow you to use with larger diameter arrows. I use FMJ's for what its worth, haven't had any issues with them.Well your gonna need a collar on the Axis to even come close to matching the durability you have now. I think the only advantage of 5mm is the ability to run a lighted nock.
Why do you want to switch in the first place? The setup you have is more durable and more forgiving in the wind. I would consider the GT Kinetic Pierce to be an upgrade to both the FMJ and Axis, if you want to use Easton the Injection should have better tolerances than your GT.
Chris Dunlap with Elk River Archery makes custom collars for axis arrows. He made me a dozen over a year ago with brass inserts, which I still use to this day. I highly recommend him, each of my arrows was within 1 grain of each other...In terms of collars, is it Iron Will and the Easton Broadhead adaptor and what else is worth looking at?
I’ve noticed minimal to no change in trajectory or impact point with a 530g axis from a 70#/30” VXR 31.5 compared to 500g…thought I was an outlier. Glad to hear I’m notDont be afraid to build an arrow around 525 to 550. People freak out and think it will drastically effect drop and speed and it's not as drastic as people think. At shorter range, the lighter arrow will fly a little flatter and drop less. At longer range, the heavy arrow will out do it.
Bows become more efficient with a heavier arrow and also have less vibration which means less noise.