I posted this question on the rimfire forum and haven't received a response so I'll ask here (where it belongs anyway).

I've always read that it's patently unsafe to rechamber a .22LR to .22WMR due to the higher pressure of the WMR AND the smaller bore diameter of the LR. The combination being just too much.

I recently read a post on another forum from a suposedly reputable gunsmith stating he's done it "many times."
Now to qualify that, I've seen quite a few very strong .22LR actions and after all, the hornet was first developed on the old Springfield trainer action. That said no mention was made of specific actions used and he seemd to imply that it was safe for any LR action.

Personally I'd never do it or reccomend it but I'm curious what you guys think. Along the same lines there was mention in a post on the rimfire page about the .22LR/.22WMR combo revolvers. Something I've also wondered about often. Are they .223 or .224 bore? Perhaps the smaller bore to fit the LR and any excess pressure from the magnum vented via the cylinder gap???

.001 will not make it dangerous.
Butch

It has nothing to do with pressure as the LR rim fire and the rim fire mag operate at the same Saami spec of 24K psi.

Personally I've never heard that you couldn't rechamber a .22LR to a .22 mag. News to me.
But pressure and safe considered. I'd say it's fine as long as the action will feed & eject the case.

Here in Oz, a lot of the old BSA single shots were converted to .22 Mag because they had a long bolt stroke.I've got an article from an old magazine on the conversion if your'e interested....pm me

Roger

The question was purely out of boredom but I did a little checking. Cartridges of the World lists the following dimentions, the first being .22LR, the second .22WMR.
Base - .225" .241"
Rim dia. .275" .291"
Rim thickness .040" .046"

I suppose the headspace issue (rim thickness) could be taken care of in the reaming but it'd seem there may be some issue with rim diameter on some guns. I do agree that in nearly any instence the 0.001" tighter barrel wouldn't add to pressure.
My major concern though is the insinuation that ANY .22LR can be thus converted. There are tons of old and questionably engineered long rifles out there. Single shots held closed only by spring pressure, bolt guns locked solely by the bolt handle - some of which are not all that well attached... Maybe the guy IS particular about what donor gun he uses but just didn't say so.