OK, so went out to try and used a chrono to check velocities. Groups were pretty **** to be fair. Nothing under 1 inch and a few fliers.
I'm now left thinking it can only be the brass having had a few firings so have ordered some Lapua from Spud.
Today I stripped the rifle down, cleaned the barrel again, took the scope off, checked the picatinny rail and torqued the action screws.
I'm going to get out again this week after the new brass arrives and I'm loading up some more ELD-X with RL16 and RS62 to see which performs the best. Might as well try both side by side with new brass.
Here's the first group I shot with the starline brass back in December and haven't been able to replicate it. Let's hope it's the brass. Also attached the velocities from the Sierra 140gr SBT if anyone's curious how the RL16 performs in a 22" barrel. Four groups from 42.5 - 44.0gr