I just re-read your post and realized you have a light bearing holster. Did you consider that the barrel plug in the holster is preventing it from seating all the way? Smaller caliber means smaller hole.
Yeah I took the plug out first to see if that was holding it up, but the slide itself is super tight in the ALS. I can get it in, but it's hard to draw and insert.
i went and used a mic on the AA slide and it is 26.3mm vs the 25.5mm on the OEM G19. The OEM G20/G21 slide is 28.5 so it fits well and no issues with loss of retention.
I'm sure some of the problem is that I'm running it on a P80 frame having the trigger guard scallops and it's about an 1/8 wider than factory making it that much harder to insert in the holster. I went as far as removing the ALS entirely to see and it's still super tight.
The P80 won't fit at all in a non-light bearing G19 holster from Safariland because of the frame at the rails. I might just shave down the scallops to see what that does.
Right now I figure that if I have to work too hard at the draw and insertion, it won't be as safe due to the extra effort required. Don't need an ND.
***me throwing time and money at problems that don't need solving***