doublegunshop.com - home Forums General Discussion Classic & Custom Single Barreled Sporting Rifles @ doublegunshop.com offset chamber rimfire conversions

Of the many things I'm NOT, a machinist or gunsmith is certainly one. So if this is an ignorant set of questions, it's because I'm genuinely ignorant.

I have seen several centerfire rifles converted to .22 rimfire by moving the chamber of the new barrel (or insert barrel) to a position where the centerfire pin strikes it.

How exactly is that done? Most of the cheaper (T-C Contender, Savage Model 24, Rossi etc.) "convertibles" move the firing pin, not the chamber. Is making a barrel with an offset chamber/bore a very complicated and/or expensive operation?

If it isn't especially complex or expensive, why are most custom conversions done by altering the action, not the barrel (for example, J. Korzinek's Ruger #1 conversions to .22 LR and WRM)?

(What prompted this is that I have a friend who has a break-action Savage Model 219 single shot rifle with a factory made ".22 Shot" barrel. It also shoots .30-30s in its other factory barrel just fine. A cheap rifle barrel with an offset chamber and bore....and here I thought it was only for advanced custom jobs....

But I've long wondered how the RF insert barrels I use in my break action centerfires were made. The Savage just reminded me to ask guys who might really know!).

Mike A.
It can be done several ways, but the easiest to explain would be to use a 4 jaw chuck.The barrel would be "centered"in the chuck and then moved off center on one axis by the precise amount necessary to move the firing pin strike from the center to the rim.
Mike

Thanks, Mike. Even I get that method, now that you've explained it!

But it sounds like a relatively easy conversion (if you're a machinist or gunsmith). So why do most of the pros go to such a lot of intricate and expensive work to change the firing mechanism and leave the chamber centered?

Does the offset chamber method produce poorer results? Worse accuracy or reliability?

There are reasons for doing a rimfire conversion either way.

An offset chamber would be used when it is desirable to not alter the action. This method requires either an oversize barrel blank so the outside can be turned eccentric from the bore, or a large enough bore to install a liner off center, such as a .22 in a shotgun.

Moving the firing pin location in the action can be simple or very complicated depending on the action.

It boils down to which method is easier for that action and the desired result.

I have done several rimfire conversions. One is a Winchester Hiwall takedown. It has two barrels, one .45-70 and the other, .22 Long rifle. The rimfire barrel has an offset chamber with the muzzle concentric. There is an extractor mounted in the barrel that looks much like a Ballard rimfire extractor that is actuated by the .45-70 extractor. This project was done to provide two barrels of identical weight, one for Silhouette, and the other for practice. The rimfire barrel started out as a 1.5" diameter blank.

I also have done a number of rimfire conversions on the Ruger#1. For these I move the firing pin and reline the existing barrel. This way I end up with a rifle that looks the same as when I started, just a different caliber.

Mike A ,
It is easy enough to offset the chamber, but the bore would be centered at the muzzel.It would complicate,some, the threading to locate the chamber at "top dead center"(or I guess "bottom dead center") so the offset bore would require adjustment to the sight heights instead of windage.There may be other reasons,important to whoever is doing the work.Of course if both rimfire and centerfire barrels will be fit to the same action,offsetting the rimfire chamber is necessary.
Mike

MikeA.

You posted your other question while I was hunting and pecking.

Probably the main reason to modify the action as opposed to offsetting the barrel would be to create a "true" rimfire action.

In theory having the bore concentric with the outside is a good thing. But unless you're trying to win a rimfire benchrest match, I wouldn't worry about it.

Thanks, guys! I guess the main difference is in the mind of the gunsmith/builder and/or the customer.

I'm a "'good' is good enough" guy, probably one good reason WHY I'm NOT a gunsmith or machinist. Many gunsmiths and most custom builders are more of a "perfection is ALMOST good enough" mindset, and willing and able to pay for it with time, skill, and dollars.

My offset chamber .22 LR and .22WRM insert barrels used in the shotgun barrels of combination guns to make them rimfire and centerfire double rifles certainly wouldn't "win a rimfire benchrest match." They do kill what I point them at very well. "Good enough."

Mike A,
Insert barrels(einstecklaufs)are great.I have used them in one or the other of my drillings to take squirrels,hare,fox, racoon,bobcat,and accidently, a whitetail( statute of limitations has expired).Never a problem(yet)with killing;even the whitetail went down within sight of where she was standing, when I shot.
Mike

Yeah, Mike, they do work. I have Kreighoff and Walther inserts in the shotgun barrels of my two Savage/Valmet 2400 O/U combinations. The one with the .222 Remington rifle barrel has a .22 LR Walther insert in the shotgun barrel, and the one with a .308 barrel has a Kreighoff .22 WRM insert in its shotgun barrel.

I zeroed them for 50 yards at the same scope setting as the centerfires use at 100. Took a lot of fiddling, but it works well. Of course then our geniuses here in CA decided that you can only use "green"--unleaded--ammo down here, so I had to go over the same process with all four barrels.... I think I'm back to a good zero for all four now, many shots and lots of cleaning later.

CCI "Quiet Green" .22 LR ammo is next to silent in the shotgun barrel, the only ray of light in this costly process. Probably the first time a 12 guage barrel has functioned as a suppressor.

Mike A,
I never tried "Quiet Green", but it sounds like it would be very useful.A 16 ga barrel doesn't make a good supressor for 22 Mag.,or HS LR for that matter.I have to use CB caps in a long barrel bolt gun around here to protect my "on again, off again" pecan crop from the "tree rats".On the otherhand, a friend has been carrying a highpowered pellet gun to his deer stand, for the rats.He has saved up enough of them that we will have them for supper in the hunting camp, Fri.He has a combo gun, maybe I can talk him into trying the "Quite Green" next year, and only have to carry one gun.
Mike