Finally got a chance to fit on the P50 HK BB and I have to say I am very pleased.
I converted my featureless my HK13E clone
And installed the BB along with a target grip and special trigger pack (housing needs to be painted)
The snap ring fitting took a little while to get co-ordinated, (as I am not the adept at installing them yet) but everything else was a simple bolt on. Not only is it a full mechanical BB, but you don't have to cut the inside guide portion of polymer lowers as the lower does not keep the BB attached to the rifle. On this one I'm using a metal lower.
Thanks Prince 50 for making this, it's a great set up.