Well, I've heard of bullet tumble, but just found it hard to believe, until today.  I went to the indoor range today and took the beater pistol which is a S+W 22A. After about 600 rounds I started noticing heavier smoke and powder embers leaving the barrel, of course I ignored this and pressed on. At about 650 rounds I lost all ability to form a group, and noticed holes the shape of bullet side profiles. I checked the gun over and found nothing wrong. I came home and did an internet search on "bullet tumble" and came up with this........"The only way powder can cause a bullet to be unbalanced before it leaves
the muzzle is for it to change the bullet's shape. One way that can
happen is the powder is just barely ignited and not completely burns. You
can determine this if the bore is very, dirty after shooting H380, but much
cleaner after shooting other powders. If there's enough powder residue in
the bore to distort the bullet as it rides over the clumps of powder
fouling, that could cause the bullet to tumble.

One solution may be to use a hotter primer with H380 powder. That'll
help burn the powder more completely and reduce, if not eliminate, powder
fouling.

The other way powder can change a bullet's shape is that it burns so fast
initially, it slams the bullet into the rifling too hard and the bullet's
rear part enlarges in diameter non-uniformly as it starts into the rifling.
But this typically just causes larger groups, not keyholing bullets.".............I think the dirty bore deforming the lead bullet I was shooting ,explains the tumble I was seeing today.yarchive.net/gun/ammo/bullet_tumble.html







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Follow up on the take down of the S+W22A. Broken firing pin in 3 pieces, and firing pin spring in 2 pieces.

Good post. Thanks for reminding us.