Hi,
You didn't say anything about a hammer weight in your tune. My 1st Crown MkII with a 500mm barrel in .177 did not come with a separate hammer weight. In fact, it couldn't accept one as the spring carrier had a long shaft on it that ran inside the spring (See Part D3 in the Crown Schematic). My second Crown MkII with a 380mm .30 (when I bought it used, now has both a .22 and a .177 380mm barrel) came with the High Power Mod and the Tungsten hammer weight. I found I didn't need the heavy Tungsten hammer and had a 12 gram Huma Brass hammer weight laying around, so I put that in. The rifle really likes it. I can tune the rifle with a lower reg pressure and I get much better ES and SD's (like single digit). I am going to put one in my first Crown now.
I should note that the tunes are a lot different with the High Power Mod not just because of the hammer weight, but also because there in a 4 mm indentation in the spring carrier so that it can grip the end of the spring. That means you either have to add 4mm to your IHS to get the same spring compression or have to get a hammer with a 4mm head to make up the difference.
Cheers,
Greg
P.S> - I second the motion - The Crown is still the King!