Backup Tactical has spent the last six months perfecting their Glock 48 Threaded Barrel. TFBTV covered the Glock 48 and 43X earlier this year so go check out that video if you’ve been living under a rock. The single-stack Glock 48 is noticeably thinner than its double-stack big-brother, the Glock 19. In order to make the Glock 48 as thin as it is, the hole in the muzzle end of the slide that the barrel goes through has a noticeably smaller diameter than the same hole in the Glock 19.
That means the barrel has a smaller diameter. Simply put, the Glock 48 barrel is thinner than the Glock 19 barrel. The big challenge when engineering a threaded barrel for the Glock 48; the small diameter of this barrel does not leave any room to machine a shoulder on the barrel for the suppressor to lock-up against.
The simple solution would be to use a barrel spacer for the suppressor to lock- up against.
But using a barrel spacer on any caliber other than .22LR never works out well in the long run. The spacer winds up deforming and battering the suppressor or accessory you attach to the barrel. The only other viable option was to determine the perfect length for the barrel so the muzzle of the barrel would shoulder up against the internal shoulder of the piston
This meant coming up with the exact right barrel length so the muzzle will shoulder on internal shoulder of the piston for all the 9mm pistol suppressors currently on the market.