to change from .222 to .223 on a single shot, would there be any accuracy change ( I want a ccombo 20ga over .223, hard to find like I want ) twist would be the factor, I think

No, not really and no twist considerations involved. If you're shooting .222 presently and are happy with it then the same bullet you're using now would work fine after a conversion to .223.

I'd question the practicality of the conversion, though. The .223 doesn't do much that the .222 can't do.

The difficult part, to do it righ, is the .223 Rem chamber needs to be cut toward the muzzle of the barrel. Think of a hole existing in a tube, and the hole is larger than the bore of the tube, but stops at a certain depth. To change to a different chambering that reamed hole needs to be deeper. But the rear end of the tube needs to remain. Can't be done.

What about a lug the barrel hinges on? That matters.

For me to make it work in my head some build up of steel with welding, then machine it back out is what would happen.

$$$$$$ in time and labor.

.222 is a great cartridge. Struggle to find ammo?

You're getting two different answers to your Question. Perhaps you can clarify your question. Are your asking:

1) I want a Rifle with .223 Rem. (top barrel) and 20ga, (bottom barrel). I have .222 Rem. ammunition (or brass cases) that I would like to convert into .223 Rem. brass by fire-forming it through the .223 Rem chambered barrel. Will this work? Will the newly formed .223 cases be accurate during future reloadings?

OR

2) I can't find the Rifle that I want, but I did find/have one with .222 Rem (top barrel) and .20ga. (Bottom Barrel). How easy is it to rechamber the existing top barrel from .222 Rem. to .223 Rem.?


Note: Understand that the barrel configuration can also be as side-by-side. This type of rifle was called a "turkey rifle" when I was a kid with the top barrel usually a 22 long rifle.

.222 brass will not fire form in a .223 Rem. The brass dimensions are very different.

.222 brass is a little more difficult to obtain.

.223 Rem/ 5.56mm brass is very abundant.

If you reload, making .223 cases into .222's is pretty much just FL size & trim.

Yessir.

But since the .223 Rem brass is so abundant, I personally would not mess with it.

The neck on .222 is quite long, as compared.

wow, this train went off the track

I'm still trying to figure out the OP's situation. My interpretation is that his Combo rifle is a .222/20 ga & he would like to convert it to .223/20 ga because of cheaper or more abundant rifle ammo. As you explained, the conversion is complex & no doubt would be expensive to do right - if even possible. If the OP only shoots factory ammo he'd pretty much be out of luck.

Probably cheaper in the long run to acquire a 223/20...if they even exist.

220, 221 whatever it takes…

Colt45-90 - This is your thread. Unfortunately, the train went off the tracks because your Original Post did not clearly define the question you were attempting to ask. Hence, my first post ^^^.

It would help if you were to restate what you are actually trying to determine.... (1) Rechamber a .222 barrel to .223 or (2) converting .222 cases into .223 cases?

A lot of Remington 788's were converted to 223 (from 222). But it was a different barrel shim/nut.

I know a guy that has 8 to 10 boxes of 222 he'd sell............

I had a REM 600 that the guy I git from had it reamed to 223 from 222 worked great. You just to find a gunsmith with a 223 reamer.

I think the problem is the dimensions are not large enough in the .223 to ream it properly, without messing up the headspace. So you might need something dimensionally larger.

If I remember right, that is the problem in getting a rifle with iron sights to line back up after you re-chamber the factory barrel in a larger bore same cartridge case. They machine a bit off the chamber end of the barrel to re-cut the chamber nice and square with good head space. You can’t do it with a single shot or over under because you can’t just screw the barrel back in and check head space. Once you machine a smidge off the chamber end of a break action it is completely screwed.

It might work out to go to a larger cartridge.

Without setting the barrel back?

If you do a little arithmetic (I used numbers off of drawings I have in QuickLOAD) you'll find that the .223 has just a hair more body taper than the .222 does, which means that without setting the barrel back you'll have a slight ridge in the chamber where the .222 shoulder begins. IF you used a .223 reamer of maximum dimensions then you might get a clean chamber without a ridge. MAYBE.

Although rechambering CAN result in headspace issues, that's not the problem here.

Yes sir. I don't see how it is possible without setting the barrel back.

Years ago, I sweet talked a friend into punching a 7mm-08 barrel into 7mm-08 A.I. O.A.L. on each brass is identical. But the barrel did get re-faced prior to making the new chamber.

I wonder if a .223 AI reamer would clean up a .222 chamber. I do not have a drawing.

That might not make sense, though, not knowing the OP's intent. If he wants to ditch .222 for .223 to avoid factory ammo availability issues, then .223 AI would not make a helluva lot of sense.

Why cant you run factory .223 in the AI chamber? Lots of people fireform brass this way and some don’t even lose accuracy.

The next problem would be the ejector or extractor. Does it have enough meat to be modified? Might wotk with no modification.

There's only two ways to obtain Ackley Improved brass (aside from .280 A.I.)

Hydro form it in a die, or fire form it.

I have only fire formed.

In .223 A.I. and 7mm-08 A.I. do a legitimate load development for your fire forming load. .223 Rem brass goes in .223 A.I. brass comes out. It will still shoot extremely tight. 1/4 MOA is more than possible. Fire all of your brass, then do a second load development, of course with more powder. And of course, your A.I. load is going to pick up more velocity.

You could do that, obviously and there's not a thing wrong with fireforming to make your AI brass. Personally, I wouldn't want to routinely shoot SAAMI .223 in an AI chamber. The idea just rubs me wrong somehow, but that's just me.

My question is why anyone would want to mess up a 222

Because .223 Rem is better.

If you're trying to modify a single-shot rifle, I would ask 'why'? The performance is almost identical and it's not like you're doing mag dumps. 5-10 boxes should be plenty to last a long time on what is essentially a hunting rifle. Save the brass and reload it, or just buy some .222 brass and have it loaded up. Midway has 5 different brands of .222 brass in stock.