The significant amount of times that one of our folks has brought a pistol to me, claiming it was consistently shooting low, I've tried the gun and found it's shooting fine with regard to POA/POI.

What I've found is the shooter was experiencing anticipatory flinch and depressing the muzzle, causing the hits to cluster lower than he/she thought they were aiming. (At the moment of anticipating the recoil they lost focus on their sights, and couldn't see they were actually shooting low.)

A session with some dummy rounds randomly loaded into their magazine (so they didn't know when they would be chambered) allowed them to see for themselves how they were pushing the muzzle down just at the moment they expected the gun to fire & recoil in their hand, which they didn't notice when they were shooting live rounds.

The first thing you might do is find an experienced shooter to try your 4516-1. Or, you might find an experienced instructor to try the gun, and then spend some time working with you to identify and correct any issues you may be experiencing when it comes to your technique.

If it turns out that the gun is really shooting that low at that distance, then the front sight might require replacement ... but first the shooter influence probably ought to be eliminated (as it's not an uncommon issue to encounter).

Just my thoughts.

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Ret LE Firearms inst & armorer