My Tandemkross compensator arrived a week or so back, my 3 extra magazines over the weekend. My M&P 22 compact FINALLY arrived today. I knew the O ring supplied by TK would not work with the M&P. It is designed for a bull barrel such as on the Ruger Mk pistols or the S&W Victory. I called TK support. It was rather obvious they had not tried installing their comp on the M&P Compact as they could offer no solution as to how to index it. Not to be slowed down by this, I had already figured some approaches...
My first thought was to use an AR crush washer. This fits OK except all 7 from my parts box, in including a couple of used ones, indexed the comp almost 180 degrees out. These washers take considerable torque to crush and I was concerned that I would twist the barrel out of the frame. On to plan B...
I cleaned the adapter male threads and comp threads, applied some primer as I was in a hurry, and some low strength Loctite. I tightened the adapter to the barrel (cold) and installed the comp and indexed it to my liking. Time for lunch.
After lunch I loaded my 5 magazines, went to my range and fired 100 rounds as fast as I could empty and reload the mags. This warmed up the barrel. Of course the adapter stared to loosen from the barrel and when I tightened it hot it went a little past the cold position. But that is why I used the low strength Loctite for this TEST. Another 150 rounds - no failures to function

and back to the shop.
I pulled the adapter and comp, put the comp in the vice and indexed the adapter against it (the Loctite was still warm). I reassembled everything and did some thinking pending my next blasting expedition.
I would like the comp to be adjustable - not permanently locked to the adapter. I believe the answer is to drill and tap a hole in the bottom of the comp for a grub screw. A piece of brass between the screw and the adapter threads will prevent damage. I have challenged the fellow at TK to come up with an answer and promised to share whatever I come up with. We shall see.
Ken
p.s. TOM BECKWITH - you said you had a TK comp on your M&P. How did you index it?