Went to their gun builder, there is a GMR 13 "rifle" with a barrel of 14.5" available, also there is a GMR 13 "pistol" with a 10.5" barrel. The pistol doesn't have a "stock" though, Are both available as restricted ?
The most ideal is actually a 10.5" barrel "pistol" but with a CQB Buttstock.
Thx for your assistance