Snake, my new 23Gen4 has very little side to side slide motion at the rear while my 1997 G22 Gen 2 is fairly sloppy. Both work 100%.
The Gen4 was very stiff when I got it but finally starting to loosen up some. Also it was hard to get the slide back on until I got about 100 rounds through it.
Which model did you get? And congrats on the new gun, I think you'll like it.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek