so my barrel from the 522SD looks like this:


notice the black barrel support block. the handguard pin screws directly into it. it is also the same piece as the breech/feeding ramp.

then i found a pic in another thread from a GSG-5:


which matches the ATI exploded view drawing:


is my barrel specific to the SD model?

a new ATI barrel doesn't properly fit because the barrel is not supported by the frame:


what the heck is going on here?
what kind of barrel do i have?

Interesting ... what date code is on yours? And/or what date is marked on the box if you have it?

It's possible there was a design change and you have an improved version...

Also try PMing ATICSR_Christopher if he doesn't chime in anyway.

Richard

date code on the firearm is BC, which i believe is 2012. i purchased it in 2012 as well.

i emailed jennifer hayes @ ATI couple days ago (2/18). previously she had responded back within minutes; have not received a response yet.
maybe i should have emailed Techservice instead.

stay tuned.

EDIT> tech service phone # (x726) went to jen's VM. she may be a do it all front person.

Agreed - mine is non-SD model and BB code (2011) but I believe it has the separate bolt and nut like your pictures.  I would have expected to hear before this if there had been a manufacturing change in 2012!

Curiouser and curiouser... please do let us know what you find out!

Richard

so, mystery solved.

i have the lite weight (LW) version of the SD. they have the different barrel.
LW barrels are only 16"
standard barrels can be either 16" or 9"

which means, 9" barrels won't fit the lite weight models and the only option to SBR a LW model is to cut/recrown the barrel.

EDIT> there is a LW pistol with a 9" barrel (GERG522PLB10).
stay tuned.