I know JHP has a reputation for causing feeding problems, but the bullets are seated as deep as they can go. They are not at minimum OAL but the widest part of the bullet is right at the case mouth. Any deeper and the tapered part of the bullet will be below the case mouth, and it seem like this would make feeding problems even worse.
Also, it's not a particularly wide HP cavity, and it won't feed in the stock Glock barrel either. Glocks having feeding problems is not a very common complaint. Also, as I mentioned before, I only tested the LW barrel with 10 rounds of factory FMJ ammo--not a very extensive test. I could not get it to feed all 5 rounds of JHP ammo fired through it with 100% reliability, which is why I suspected the barrel may have been part of the problem.
As for crimp, yes, I was measuring it right at the case mouth. When chambering rounds, I never ride the slide forward--I always release it when fully retracted or release it using the slide lock. The slide goes all the way forward except for maybe the last 1/4", where no amount of coaxing will get it into battery. I also have to remove the mag to get any chambered round out, a problem which a Glock armorer told me is "normal." So, as you can see, the pistol has provided me with some reason for suspecting that it may be contributing to the problem.