Does the job, would be nice if it would stay in place. - NcSTAR ShotGun Rails Bayonet Mount Remington 870

I mounted this on my Mossberg 500 ATP, which I found out was juuuuust out of spec in a few areas compared to modern 500s. To include the outside diameter of the magazine tube and barrel locking screw. This meant in particular the end cap didn't fit. About an hour with some coarse sandpaper, and I was able to remove enough aluminum to get it to fit and remain secured with the locking crossbolt. The piece that fits over the magazine tube has a bit of the opposite problem. With ot tightened down to the point I'm genuinely afraid I'm going to shear off the crossbolt, it still moves back and forth and tries to rotate around the magazine tube. Not enough for me to say that it is loose, but enough to make sure you won't mount the bayonet on your first try. It's annoying at worst, really. I bought the shotgun and this bayonet mount specifically because I knew I'd never be able to own a real trench gun, so I made my own. In the end, it came out alright. I just wish it would stay centered. It just drives me up the wall when I look at it and the blade of the bayonet is cocked to one side.