I am always amazed at how much difference there is in point of impact between varying bullet weights out of a pistol. Hell, I find significant variance between different brands even with the same bullet weight. If you are serious about the readiness of your carry gun as a defensive tool, you absolutely must verify the point of impact, and perhaps adjust sights accordingly, with the defensive ammunition you carry.
Recently I shot my go-to training Glock 19 and immediately recognized that it was impacting constantly high when using the cheapo 115 grain Blazer Aluminum training ammo that I have on tap. In fact, even at 10 yards I was impacting high, and even consistently to the right. The windage adjustment is doable even with most iron sights, but elevation is a challenge with most fixed sights. Therefore, matching a gun with the right load for it is important.
Training ammunition is what it is, so I don’t worry too much about it in this gun, as I don’t even carry this gun, so I don’t have it specifically sighted in for a dedicated carry load. However, the amount of variance seen here would certainly throw you off shooting a match.
At 10 yards my group was more than an inch high and slightly to the right as well, discounting the one shot that is significantly lower (it seems I always throw at least one):
I sent a B16 target to 25 yards and the group was so high that all rounds were outside of the black. So, in order to better gauge what was happening I send a small silhouette target to 25 and aimed at the drawn dot. As you can see, the group is significantly high, except for the one that I tanked below the dot, but that was me, not the gun. the group is also to the left, which seems odd, as the 10 yard group was to the right, but it might be the way I was seeing things in the terrible indoor range light.
The group, minus the one shot I pulled low (again, always at least one) is a four-inch group at 25 yards and easily fits within the black of a B8 or B16 target, so not bad for off-hand shooting with crap ammo. However, the point of impact is, as can be seen, significantly high compared to the point of aim:
So, the moral of the story is, know the point of impact for your gun with its practice ammo before you do anything where it counts, and more importantly, know the point of impact of your carry ammo in your carry gun. I have found that this particular G19 will be six inches different at 25 yards with different bullet weights.