I was in the range yesterday and I was shooting dismally with the G19. Shot 200 reloaded lead rounds because I was missing badly (head shots - IPSC board) at 10 meters. I normally shoot only 150 rounds at most. We already noticed that the bullets were making keyholes right at the outset. I usually clean the barrel every 50 rounds whenever I use lead bullets but this time, the barrel was really fouling a lot. Anyway, I was really shooting very badly so I decided to shoot all my bullets in order to improve my accuracy, to no avail. Then, I decided to blame the bullets. I bought ARMSCOR factory FMJ ammo so that I can check whether it is operator error or bullet/gun related. Shot relatively tighter groups (1.5") with the ARMSCOR ammo even at 12 meters. No misses. Bullet related.
I've had the G19 for a long time now and this is the first time I've used factory 9mm FMJ ammo on it. When I first got it, I was using lead reloads up until the time that I got the G21. I was shooting better with the G21 so I stopped using the G19. The G21 has a Wilson Match barrel which I use for practice and competition and it is pretty accurate.
Last year, I started using the G19 again, this time using FMJ Armscor reloads and I was shooting better. Then, when FMJ became expensive, I started using Teflon reloads. I decided to try shooting with lead reloads again and had them reloaded in one gun store - accuracy was still acceptable. Then I switched to another gun store that was nearer my place and that's when I began having bullet related accuracy problems and keyholes. I used to get my .45 lead reloads at that store before but stopped when my G21 wouldn't cycle.
I think that the problem of accuracy and keyholes may be related to the bullet diameter. The diameter is less than standard and the not so tight fit may allow the non-coincidence of the bullet and bore axes. The bullet would leave the barrel skewed and the gas would induce a torque on the bullet, hence the keyhole effect.
I did some measurements of head diameters:
9 mm Lead (from THAT gun store)
I guess Glock OEM barrels prefer factory FMJ ammo. It is a very accurate pistol and very sturdy too, plus it is easy to conceal. You just have to use the right bullet. You get what you pay for really. I'm glad I didn't sell it.
I will write the owner of that gun store. He probably doesn't have any inputs from his customers. If he writes me back then I'll try going back to his store.