Convert .22LR to .25acp??

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44 AMP

Staff
A friend asked me to put this idea out on the web, so here goes...

He heard someone talking about how .22LR while better than it was, is still scarce in places, but there always seems to be .25ACP on the shelf...

SO, he's asking, is there a .22LR (or magnum) semi auto or lever action that could be converted? And, who would be willing to undertake the work??

What rifle(s) might be a suitable basis for the conversion?

He figures a tube magazine would be the best way to go, to avoid also having to adapt the a box mag.

NO practical use intended, just a technical exercise, so far..

he did mention some data about a 35gr HP slug at 1100fps, which would be small game capable, I would think, but that's for later..

Thoughts? pro? cons? (on the conversion, not what one could use it for)

Thanks!
 
F

FITASC

New member
The firing pin presents an issue. I do not know at the moment what the pressures generated are between the two. The price of .25, unless he reloads, is VERY high. .22 is available by mail order from multiple sources - perhaps he might want to consider that aspect as well in this exercise.
 
S

Snyper

New member
I suspect it would be about as easy to build an entire gun as to attempt any conversion with as many differences as there are between those cartridges.
 
R

Reloadron

New member
jmorris, wanted to pass along a thanks for sharing that thread link. Actually an interesting read and the guy made himself an interesting project. He was over a year into the project. Then moved on to the .32 ACP.

Thanks
Ron
 
U

Unclenick

Staff
The .22 RFs (long, and long rifle) are rated by SAAMI at 24,000 psi and the 25 ACP is rated at 25,000 psi. This is not enough pressure difference to matter. The groove diameter of the rimfire is 0.222", while the 25 Auto uses 0.250" groove, an increase of 0.028", which is too much for squeezing the little jacketed bullets down if you expect any sort of accuracy. So you are in for a custom rifled barrel blank to start.

The rest is getting the firing pin, extractor hook and ejector to all line up correctly with the new round. As far as anything short of making a new bolt from scratch goes, I'm drawing a blank on what would be good to work with.
 
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FrankenMauser

New member
No experience here. Just my thoughts....


Modifying a magazine (or three) would take some careful work, but I think I would use a 77/22 for the job ... if I had a wild hair prompting me to take on the project.

It's not a semi-auto, or a lever gun; but it's where I would turn.

Reasons:
1. Solid action. No cheesy parts to deal with that make modification more difficult.
2. The .22 LR magazine has enough meat in the parts and enough room in the case to be modified for .25 Auto. (Trigonometry, careful calculations, and a mill would be a must; unless some one wanted to hand-file each cartridge slot in the magazine rotor.)
3. With a .22 WMR breech bolt, the only modifications needed for the bolt would be converting to centerfire.
4. Converting to centerfire, though more complicated than on something like a Marlin 700/800/900 series rimfire rifle, is fairly straight-forward and (done properly) will result in a very robust striker assembly.
5. Barrel changes are easy and straight-forward. Older versions just have V-blocks for barrel retention. Newer versions are threaded. (No pins, welds, rivets, or other cheap rimfire design craziness to deal with.)
6. I'm a fan of the 77/22s, anyway.

Cons:
1. Ruger discontinued the 77/22-series. No new rifles available, unless N.O.S. is found.
2. Ruger discontinued the 77/22-series. Used examples are now climbing in price.
3. 77/22s have never been cheap - even if beaten, battered, and left to rot.



Alternatively, a 77/22 Magnum could be used, to avoid having to track down the magnum bolt (or modify a .22 LR bolt), but the magazine may require more work to make it feed.
Or, a 77/22 Magnum could be fitted with a 77/22 trigger plate (bottom metal) and magazine. Then only the barrel change, magazine modification, and centerfire conversion should be required.


And, of course, the above magazine modifications could also apply to a 10/22, which would meet the semi-auto qualification.
 
D

dakota.potts

New member
I have seen several conversions of this nature on weaponsguild.com but I don't know if I've seen any by professional firms.

There is a Midway USA video where Larry Potterfield takes a .32 Rimfire rifle and converts it to a centerfire rifle (the details I don't remember). The bolt face would have to be drilled out in the center for a new firing pin, at least, the new shape of which might be able to replicate the old firing pin (as is done on the Vetterli conversions, using the shape of the old strike as a firing pin housing)

A .25 conversion would involve a .25 caliber barrel blank too, which may or may not be cost prohibitive (although the whole job might be).

I know tube magazines can have issues feeding straight cases, I don't know if the .25 has enough of a rim to help mitigate this issue, but I think it would definitely require tuning and maybe timing coming from a .22LR unless you got really lucky.

Depending on the strength of the action, 5.7X28mm comes to mind as an interesting choice. It has always been available at any decently sized gun shop I've seen (and relatively inexpensive), uses a standard .22 caliber barrel, and has really good velocity for small game. A box magazine including maybe some type of pistol magazine could work. That would be a very cool small rifle cartridge.

If you did want to rebarrel a .22 to .25, I'd investigate starting with something like a Ruger American, Marlin, or Savage bolt action. All of these magazines are relatively similar in shape to a pistol magazine so there's a possibility you could find a .25 pistol magazine with similar enough dimensions to modify the rifle to accept it. I've seen this done on Enfields and Mausers with .45 ACP
 
S

Scorch

New member
A few thoughts on the subject:
* The cost of the barrel alone would be enough to discourage most people (maybe $150-ish). Then there's the chambering and profiling part (another $300-ish). Lots of work, little gain. But it sounds fun, if for no other reason than to say you've done it and no you won't do one for anyone else (met a smith once with a Win 94 in 45 ACP. No, he wouldn't make any more of them).

* The donor rifle would have to be cheap enough to sacrifice (or not care about cost for a more expensive rifle). Yes, the Ruger 77/22 magnum could be a good donor, as would a 10/22 Magnum. Either would be expensive as they have been discontinued. Basically, little else to do other than rebarrel and change firing pin location. Then there's the magazine . . .:rolleyes:

* One reason there's always lots of 25ACP on the shelf is that there are few people who use them. Low sales volume, therefore the supply lasts indefinitely. Price for the ammo is also negligible, so it would not be too expensive to shoot. But while it may appear the supply is good (due to low sales volume), you could probably clean out all the 25ACP ammo from an entire city's sporting goods stores and not have enough ammo for a decent range session.

* I am not sure why people are still complaining about 22LR ammo. Look online, it is available just about everywhere. No, it doesn't cost what it cost 10 years ago, but neither does food, gas, beer, chips, (damn, now i'm hungry).

So, basically, yes, it could be done, but not by me.:D
 
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natman

New member
Once you add up the cost of the donor rifle, then new barrel, the rimfire to centerfire conversion, the magazine mods, etc, etc - well you could buy a LOT of 22 ammo for what it would all add up to.

Anything is possible, but this conversion is not even remotely practical.
 
4

44 AMP

Staff
Thanks for the comments so far.

It's not about practical or cost-effective. It's about can you do it, and what would it take.

I remember there was a Marlin (I think) rifle that had a firing pin that installed one way was rimfire, and the other way centerfire. Can't recall the model, but its long out of production, I'm sure.

He thought the tube mag would involve fewer things to worry about, just the lifter, and maybe the cartridge stop...

What I was concerned about, a bit, was pressure, but seems they are close enough not to matter, so a blowback semi shouldn't be a major issue, beyond change to centerfire and extractor fitting...assuming one can get the feed system running right...

The bolt action is no doubt a bit more "practical" and sounds simpler, other than the mag issue. Probably a housing could be made to take a pistol mag, but if the tube mag can work, it would provide a higher capacity.

And, yes, a custom barrel or having the original rebored would be in order...

again, thanks, and any idea who might be interested in taking on the project??
 
T

tangolima

New member
25 acp could be always on the shelf, but it is currently about $0.30 a round. You can buy 22lr no problem if you are willing to pay this much.

Feasibility of the conversion, anything is possible if money is no subject. But one can only assume it is really the case.

Thompson center is one design that has reconfigurable firing pin. Same frame can fire center fire or rim fire, depending the barrel installed.

Direct blowback semi auto is actually simpler than bolt action. You don't need locking surfaces, just a spring to keep the bolt close. No fuzzing with headspace either.

Why climb the mountains? Because they are there. Only a few can say that with straight faces and don't feel silly. This one is mighty hard.

-TL
 
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natman

New member
Direct blowback semi auto is actually simpler than bolt action. You don't need locking surfaces, just a spring to keep the bolt close. No fuzzing with headspace either.
Click to expand...

Direct blowback may be mechanically simpler, but it's a LOT harder to design and get working. Getting the right balance of bolt weight and spring strength is not easy.
 
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natman

New member
It's not about practical or cost-effective. It's about can you do it, and what would it take.
Click to expand...

Good, because it's not going to be cost effective. New barrel, new firing pin, extractor mods, bolt face mods, magazine mods. All so you can fire ammo that's more expensive and no more available than the ammo the gun fired in the first place.

I remember there was a Marlin (I think) rifle that had a firing pin that installed one way was rimfire, and the other way centerfire. Can't recall the model, but its long out of production, I'm sure.
Click to expand...

Sounds like the Marlin 1892 lever action. It had two different firing pins that could be swapped out for 32 RF or 32 Colt. It's long out of production, as is the ammo. The trick is that it was designed from scratch that way.
 
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T. O'Heir

New member
"...maybe $150-ish..." Where you going to get a long .251" ID barrel for that?
"...what would it take..." Money and lots of it. snicker.
The tube mag would require replacing altogether. Far too much difference in cartridge diameters. The .25 has .301" diameter at the rim. A LR is .275". .291" for a .22 Mag. Probably doable if you could find a .25 Stevens Short.
And you'd need a different follower. Plus converting a rimfire to cf.
 
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natman

New member
Green Mountain.
I'd bet they could provide one for under $150.
Click to expand...

I'll take that bet. ;)

I contacted them and they don't make a barrel in the appropriate bore size. Probably because nobody in his right mind would do such a conversion. :rolleyes:

25 caliber rifle barrels use a bore of .257 and are too big for the .251 25 ACP bullet. :(
 
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