I had the same issue with my 420. I spoke with the service center in Idaho and was told to back out the turret screws 4-5 times and pull up really hard. Then push down to lock the turret, then tighten the screws. That worked for me and no more issues. You have to make sure going forward to...
I am using one for loading 300 prc on my Forster with no problem at all for clearance. I did have RCBS make a custom seater stem to load the 230gr A-tip. My oal is 3.755 so it should be fine.