I recently installed the Slug Power Kit in my Mk3 because I was running up against the limits of velocity while shooting HN 27gr slugs. So far these are unquestionably the most consistent slug I have been able to shoot out of this gun (in .218), grouping even better than the hybrids. Without the power kit I was able to get them to about 930 out of the 600mm barrel while maintaining some semblance of harmonic tuning. With the power kit I am pushing them at 990 and the gun feels and sounds settled. Groups are better at 50, too.
SD is about 2.0 with an ES of 7fps, so I know that the gun is working well and velocity inconsistency is not an issue. Groups at 50 are consistently around .3-.6" if I do my part and there is no breeze. Not bad.
Problem is that groups open up far more than they "should" at 100. I see groups of 3" plus with not much consistency at 100. There is a very light variable breeze but it is low single digit speeds. It should not have the effect that I see. This is much more of a deviation between 50 and 100 than I see when shooting my 17HMR, for example, so I don't think it is only the shooter.
This is all with the STX Superior liner (1:24 twist). Based on some stability calculators online, it seems that the current setup is marginal at best in terms of calculated stability whereas if I shot with the 600mm Superior Heavy liner with the 1:16 twist, things improve (theoretically) dramatically. Anyone done an apples to apples comparison with these liners in the Wildcat/Maverick and HN slugs?
SD is about 2.0 with an ES of 7fps, so I know that the gun is working well and velocity inconsistency is not an issue. Groups at 50 are consistently around .3-.6" if I do my part and there is no breeze. Not bad.
Problem is that groups open up far more than they "should" at 100. I see groups of 3" plus with not much consistency at 100. There is a very light variable breeze but it is low single digit speeds. It should not have the effect that I see. This is much more of a deviation between 50 and 100 than I see when shooting my 17HMR, for example, so I don't think it is only the shooter.
This is all with the STX Superior liner (1:24 twist). Based on some stability calculators online, it seems that the current setup is marginal at best in terms of calculated stability whereas if I shot with the 600mm Superior Heavy liner with the 1:16 twist, things improve (theoretically) dramatically. Anyone done an apples to apples comparison with these liners in the Wildcat/Maverick and HN slugs?