Thats odd because i mic the 458 FTX which comes out to .458 and in a MMP Orange i get .506 with only slight pressure on the caliper. It might go to .504 if i give it a squeeze.

Oops my bad, i just dbl checked. its .505

Yep the MMP 3P-EZ is pretty short and comes out to about .501 depending on bullet.