.22 Mag bore

[H Richard]

Trying to help a friend. He was testing 3 .22 Mag pistols. S&W reasonable groups, clean holes. High Standard same. But a Taurus (like brand new) was key-holing nearly all the shots. All shot at 10 yards. All 3 crowns look excellent, and all are in like new condition.

I know that both .22 and .22Mag. are barreled 1-16", but what is the bore of the .22 mag supposed to be?

To my knowledge key-holing usually starts with an over size bore, I think.

Any way to measure a bore without a expensive tool or official measured rod?


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[glenwolde]

According to the SAMMI spec sheet...

.22 Magnum
.220 Bore
.226 Groove

.22 Long Rifle
.217 Bore
.222 Groove

https://saami.org/wp-content/upload....1-Rimfire-2015-R2018-Approved-2018-06-13.pdf

The above is why S&W would never fit a .22 mag cylinder to a Model 17. But they would fit a LR cylinder to a Model 48. Their guns were bored to spec. It's also why I'm not overly fond of convertibles.

As to what Taurus does, who knows. First I'd be sure the barrel was clean. Then I'd might pull a bullet and use it to slug the bore and measure it with a micrometer. I've never slugged a .22 bore though. I never found a need. There might be something better to use like a .22 BB or pellet.

Or just send it back to the factory. Taurus has a lifetime warranty. Send a target with it, listing distance and ammo.

 

[Bastogne71]

According to the SAMMI spec sheet...

.22 Magnum
.220 Bore
.226 Groove

.22 Long Rifle
.217 Bore
.222 Groove

https://saami.org/wp-content/upload....1-Rimfire-2015-R2018-Approved-2018-06-13.pdf

This is not the correct data for the 22 WMR. It should be: Bore 0.219"; Groove 0.224". You listed data for the semi-obsolete 22 Winchester Rimfire.

No matter though. I agree since the other two pistols worked well, I think that rules out an ammunition problem and we can assume that there is something wrong with the Taurus. If it were mine, I'd send it back to Taurus for repair. No firearm using the correct ammunition should ever keyhole at ten yards.

 

[Murdock]

Leading of the bore does a fine job of making bullets tumble. I had a M17 that could not abide Winchester T22 ammo and bullets tumbled at 25 yards after only a couple of cylinders of the stuff shot through it.