It "wiggles" when the barrel is just sitting in the slide without the recoil spring installed or slide mounted on the frame.

I'll try assembling it fully now...

OK, with the S&W factory 9mm barrel in the fully assembled Franken40, it doesn't move by pushing left and right by applying finger pressure on the top of the barrel locking block (the part that locks into the ejection port).

By pressing strongly on the right side of the locking block, I can feel the barrel kind of click over a tiny bit and then by prying on the left side it clicks to the right, it's pretty small amount of movement. When I work the slide, it falls back into the center, at least that's what it seems like.

I hand cycled my new 17 round magazine and my 2 12 rounders with ammo and the mags feed FMJs, at least by hand.

I note that when I put the 40 barrel back in, the barrel can forced to the left and right a little bit too, it feels less than with the 9mm barrel.

I'll try to make it to the range tomorrow. I hope it doesn't blow up.

I could have gotten a Storm Lake barrel made for the 40 slide for $90 more. Cheapskatism is a horrible illness that often causes me to wind up spending more money, not less.