The 15-22 is .22LR only. There is no gas tube.
Do NOT use a receiver block unless you want to destroy the upper and possibly the bolt guide rail.
Use barrel vise jaws.
If you can hold a barrel with your hand to 20 Ft. Lbs. I do not want to shake your hand.
Those ambi charging handles are the nicest ones for the 15-22 available.
(From your favorite online retailer)
The only AR-15 thing compatible with the 15-22 upper is whatever mounts on the picatinny rail.
You need an adapter for the hand guard.
The 15-22 A-2 front sight slips right on.
Thanks for the update.
What is the M&P AR15-22 Sport? I only see the M&P 15-22 SPORT in a few different variations.
The flash hider looks like the standard A2 style they have on all their standard barrels.
But not their (standard) or (compliant) models
$799 "down" to $449
That's odd because a shroud covers something. Maybe they think the re-director is one since it covers the flash hider.
A barrel shroud covers (shrouds) the barrel.
A rifle is a long gun, not a long rifle.
The .22 and 5.56 are the same caliber
The 15-22 is an AR "style" rifle, but nowhere near an AR or AR clone.
.22LR is decent for hunting, but for real SHTF, an AR-10 is the ticket.
You will still have a gap.
Unless you cut a notch in the bottom part of the rail to fit around the pivot pin boss. Even then I'm not sure it would be flush.
Look at the side profile of the upper. The front of the mag well is in front of the picatinny rail.
The first thing to look at is if the magazine is being used as a steady rest or grip. Don't touch the mag.
The second thing would be if the ejector is in the proper location.
Post a pic of the ejector with an empty mag and the bolt locked back.
Some barrel nut wrenches fit over the flash hider...