Keyholing with Gallant bullets

[GyroF-16]

Just loaded 100 rds from my latest lot of Gallant 147 gr bullets. Same load and COAL as my last… 5000 or more.
But these seem to be tumbling- making oblong holes in the target about 20% of the time. The holes have a black oblong mark on one edge of the hole (the bullets are coated in black polymer).
Any ideas?
Would smaller diameter bullets do this, because they wouldn’t fully engage with the rifling in the barrel?
I don’t think the barrel is shot out, as it only has 15,000 rounds through it, and the other 80% of bullets fired seem to track straight and make round holes.

I’d appreciate any input.

[Spartan1980]

Smaller bullets? If so, that would be my first suspicion.

[WDR]

Yeah, measure a few and see what diameter you have.

This bodes "not well" for the box of those same bullets I have...

ETA: what gun specifically?

[OlongJohnson]

Different bullets, but I've had CCI powdercoated .22LR keyhole at 7 yards from a Sig P250 that shoots other stuff well. Same ammo shot okay from a Buck Mark.

[SecondsCount]

Do you have a set of dial calipers to measure and compare to a known good bullet?

[GyroF-16]

They are Gallant 147 gr, .356”
Shooting them out of a Beretta 92 LTT Elite.

I measured 20 bullets from that lot a little while ago. Every one of them measured .3565” on my caliper.

That’s the same diameter I’ve been using all along. I tried some .357 from them, but they grouped slightly larger in my gun, and had to be special ordered, so it’s been .356 for probably close to 10,000 rds.

Since they’re not smaller than expected, I’m wondering if they’re starting to break up in flight. Some of the holes actually look like doubles, with the black mark on only one edge.

I’m really puzzled by this, and am hoping for someone to chime in that’s seen something similar before.

[edison]

What's the velocity?

[GyroF-16]

What's the velocity?

Velocity is about 900 fps.

[Jim Watson]

What kind of target? A limp paper target can tear in a way that looks like a key holing bullet.

But things can go awry without obvious cause. I had some plated bullets to keyhole, a local guy got them in wholesale from a maker in Florida. They looked the same profile and miked the same diameter as the Xtremes I had been loading but they did not shoot the same.

[dsa]

Have you shot them out of this gun before? It wouldn't be the first time I heard of a Beretta needing a slightly larger bullet (.357 or .358) to obtain better accuracy and prevent leading.