Is that barrel rifled ? I remember the .410 revolvers had to have rifled barrels.
Remember Boys and Girls, if it didn't start life as a PGO you'll need a stamp to cut the barrel...
or buy one in the white and keep proof of it.
sarco and numrich are the places to check if you want to find 'in the white' unfinished receivers and they're usually cheap too.
I am absolutely not surprised at the response of the Shockwave 590 at the SHOT show 2017. Nor am I surprised that Mossberg has teamed up with Marty (Shockwave) to produce this for retail. Talent, Integrity and Hard Work = this kind of outcome.
I feel like I need to get a selfie and an autograph.
Now all we need is for Marty to team up with KAC to make the Khimera...