I should have mentioned that the Adams Arms kit is identical to what the S&W piston rifles have...I think they were actually supplied by Adams, but not certain.

As far as "Tilt" goes, the piston rod is in direct line with the bolt, so when it cycles the bolt it goes straight back in a horizontal line. Mine shows no evidence of tilt after 4 years of active shooting.

Their web site shows the same parts that are in my rifle:

Carbine Length Piston Kit