Rechambering single shot .22 LR to .22 magnum?

July 16, 2011 19:02

My son has a rossi combo, and there is this barrel on GB: http://www.gunbroker.com/Auction/ViewItem.aspx?Item=241379457

Since .22 mag has a .224 bullet, and .22 LR is .222, could the barrel be rechambered and the bore lapped the .002? How easy would this be to do myself?

Comments

10 comments

beantownshootah

July 16, 2011 21:30
I think the CHAMBER conversion is relatively straightforward though I'll leave it to one of the resident board gunsmiths to wax eloquent on the details.

Personally, never having done this, I'd be inclined to hire a gunsmith to do this for me (rather than mess around with renting a reamer, checking headspace, etc).

You may also have to tinker with the extractor/ejector to work on longer/thicker .22 magnum cases, so there may be a bit more to getting this to work than just the rechamber.

On the bore dimensions, that's a can of worms.

At the very least, before you break out the lapping compound, consider that there is actually a good bit of variation in bore size in nominal .22LR barrels with some of them being slightly oversized. Its probably worth measuring the bore or asking Rossi what its specs are, before proceeding.
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Bill DeShivs

July 16, 2011 21:52
You may also have firing pin problems. The WMR case is larger than the LR, and the pin may strike too far inward.
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Fatstrat

July 17, 2011 05:07
Also the extractor may need some reworking.
I rechambered an old Polish Cugir .22 military training rifle to .22 mag. Rechambering the chamber was the easly part. Opening up the bolt face was much harder. When finished, it shot great. But barrel erosion from squeezing an oversize bullet through is another factor. Probably best to drill out the bore and install a .22Mag barrel tube IMO.
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11b6r

July 17, 2011 06:52
In addition to what they said up there ^^^, pushing a JACKETED bullet (most 22 mag is jacketed) thru an undersized bore with the wrong rate of twist not good. The convertable 22 reolvers with 2 cylinders use the 22 magnum bore diameter.
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nononsense

July 17, 2011 07:13
roadchoad,

I know nothing about 'waxing eloquent', especially given my screen name but I can offer some pragmatic advice from both my experience and knowledge base.

In no particular order of process:

- .224 barrel liner will run you about $100.00 + the labor of the gunsmith to drill and ream the barrel for the liner.

- Reaming/headspacing a new chamber will run about $75.00 approximately.

- Extractor work and fitting $25.00 (guessing here)

So for the small price of $250 - $300.00 you can have a $75.00 barrel.

Sleeving a chamber has been done under several sets of circumstances except here you will not gain anything due to the difference in bore/groove dimensions. The point is mute, you still can't do it.

NO you CANNOT lap a .22LR barrel to .22 caliber centerfire dimensions. Lapping as a process is reserved for polishing the interior of a barrel not removing excessive amounts of material. In addition, if you did attempt to lap this barrel, you will end up removing the lands before you achieve your goal. The grooves will not magically appear through lapping. Rifling is created through cutting the grooves or impressing the grooves with a button or hammer forging.

Lapping a finished barrel also requires the muzzle be cut off about an inch due to the action of the lapping producing a bell at the muzzle.

Lapping by an unqualified individual will general produce a completely ruined barrel since they lack the experience and techniques required to get the job done correctly.

NO you cannot have the barrel re-bored and re-rifled since there is not enough of a difference in the dimensions to allow for the process.

Look for a new barrel chambered the way you want it.

Best.
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roadchoad

July 17, 2011 07:14
Hmm, glad I asked! Didn't think about the extractor. The firing pin, since this is a combo gun, is round ,and the center of it hits on the edge of the cartridge. That is why I think this would work.

See this pic I took of the chamber:

Nononsense, are the lands really only .001 high? Seems like they'd be deeper than that. Do you know hat the pressure might be like if I did not have a .224 bore? The action is overbuilt and the chamber has walls over 1/4" thick.
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nononsense

July 17, 2011 08:06
roadchoad,

I'm on the run with several projects right now but if memory serves me correctly...

.22 Long Rifle uses a 0.216" bore dimension and a 0.222" groove dimension.

.22 Magnum uses a 0.218" bore dimension and a .224 groove dimension.

It's your face, do as you see fit.

Best.
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tsr1965

July 17, 2011 08:45
quote:Originally posted by roadchoad
Hmm, glad I asked! Didn't think about the extractor. The firing pin, since this is a combo gun, is round ,and the center of it hits on the edge of the cartridge. That is why I think this would work.

See this pic I took of the chamber:

Nononsense, are the lands really only .001 high? Seems like they'd be deeper than that. Do you know hat the pressure might be like if I did not have a .224 bore? The action is overbuilt and the chamber has walls over 1/4" thick.

roadchoad,

Several manufacturers make 22LR/22WMR revolver's that are convertable. They always barrel the revolver with a 0.224" groove dimension. I would not rechamber that barrel. Chances are it might work, but for how long will it handle the excessive pressure? It might blow the first round, the 17th, the 2 millionth, or it might never blow. For the cost of another barrel, is it really worth it?

On another note, from your picture, you are going to need to go see a gunsmith n the future anyway. Excessive dryfiring has peened your chamber pretty severely.

Best
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roadchoad

July 17, 2011 10:33
The barrel came like that, it's a Rossi, what can I say?

Well, you guys talked me out of it, thought it might be a fun project to take on.
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spasmcreek

July 17, 2011 16:40
have rechambered revolvers cylinders & single shot rifles to 22 mag sometimes have to shape bolt face and have had to take a little off of reamer pilot...examples are a ruger bisleys to 22 mag with up to 18" barrel...savage cub bolt rife , savage steven favorite repros from late 70's...NOT old favorites as pins will not hold headspace..have had no problems as not many rifles are that tight a bore...pick strong actions....
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