Home Forums Hunting & Shooting Gunsmithing Ithaca 37 barrel fitting

I am thinking about looking for a full choke barrel for my Model 37 16 gauge.

From my understanding the barrel will have to be fitted to the receiver by way of machining a little at a time off of the mating surface of the barrel until it can be turned in to the receiver.

What is done if the opposite is needed? A little too much headspace I guess is what I am saying. Barrel turns in too freely.

Anybody know of a competent smith and an approximate price?

Someone is feeding you a line of BS.

The Bbl will fit loose in the receiver....until you un-thread the mag tube cap to tighten the Bbl in the receiver.

The difference is of the first interrupted pitch or lack of....depending on receiver &/or Bbl vintage.

It's Ithaca themselves that is feeding that "line of BS."

OP, that's correct. Not all Ithaca M37 barrels are interchangeable, and not all barrels that are interchangeable end up with the correct head spacing. It's not how loosely the barrel turns in the receiver that creates the issue, it's how far the barrel extension extends into the receiver. After all, the barrel doesn't screw into the receiver on an M37. It slides in then turns to engage the locking threads. The bolt locks in top of the receiver in a M37, not into the barrel extension like many newer designs. Headspacing needs to be checked, especially if you are mixing and matching receivers and barrels from different years.

In fact, some newer M37 barrels won't fit some old M37 receivers at all without having the receiver milled and having an insert installed to accomodate the newer barrel's thread pattern.

I recommend you deal with the gunsmiths at Ithaca. Their service is stellar. The best I've experienced with any company or individual. I've used them several times and they will work on all years of M37, whether they made it at their factory in Upper Sandusky, or it was made at Kings Ferry or Ithaca.

https://ithacagun.com/factory-service/


BTW, if you do have a barrel that does fit the receiver properly but turns in tightly, this is usually due to the barrel yoke split that is mounted on the magazine tube being too tight for the barrel. This is because the tighter the barrel yoke split is, the more upward pressure is exerted on the barrrel. If you try to attach another barrel with the yoke split too tight, then you are essentially attempting to put the barrel in at a slight angle. You can loosen the yoke split screw a bit and the barrel will turn in freely. Then you can adjust the yoke split after the barrel is in. There are slight variations in the outisde diameter of barrels - like when going from a slug barrel to a vent rib barrel, or from a rotoforged barrel to a newer designed where all the went rib posts are machined as one part with the barrel.

The yoke split need to be loose enough to turn the barrel in the receiver easily, but tight enough so that when you back the magazine cap out to secure the barrel, that yoke split doesn't twist on the magazine tube or allow the barrel to twist while attached to the receiver. The way to test it is to install the barrel, make sure it turns in the receiver easily, if not loosen the yoke split a little, then tighten the magazine cap to the barrel stud, then tighten the yoke split screw, but just enough to make sure the yoke split can't be grasped and twisted on the magazine tube with the barrel installed, ore the barrel twists while in the receiver and on the magazine tube. You may end up with a siutation where the barrel is a little tighter to take off than it was put put on.

The M37 is a great gun. But it has some excentricities. It's not the same as the mass produced shotguns made today. It needs to be tuned a little each time you change a barrel out.

IIRC, Ithaca 37 bbls being put on receivers with a serial # pre-880K (?) (serial # on the thin forward edge of the receiver) need to be fitted. I could be wrong . . . .

I have an older 37 (1957). When I was looking for a slug barrel Ithaca told me that all 37s made before a certain year would accept any barrel made before that year but that any 37 or barrel made after that year needed to be fitted. Unfortunately, I do not remember the specific year.

The big change was the switch from actual threads on the barrels and in receivers to grooves that look like threads but are straight with no pitch. Both are interrupted for takedown. Grooved barrels are interchangeable and threaded barrels need to be fit.

I’ve never fit one that over indexed but I would guess it could be chucked in the lathe and the shoulder “stretched” or swedged by applying pressure to it with a smooth rounded tool. I’ve used this method to get used barrels to index on rifles with complex breaching systems or length sensitive features like gas ports and dovetail cuts where setting it back a turn would cause more issues.

From Ithaca's website:

Barrels & Receivers

There are nearly two million Ithaca Model 37s already in the field, and many of their owners would like to outfit them with a new barrel. Just how that aim is achieved depends on the serial number of your gun.

Model 37® firearms with a serial number below 855,000 have barrels that are removeable but not interchangeable with our currently manufactured barrels. If your M37 was made before the 855,000 mark (which occurred in 1963), we will be able to furnish you with a replacement barrel for it, but you must send your gun to us for the barrel to be fitted. The process includes machine removal of existing threads, insertion of adapter and re-threading of receiver and re-bluing. Please note that once this is completed you will not be able to reuse your old barrel. Cost for this process is $750.00 for the adapter, the barrel, and re-bluing. This also includes a choke tube kit.

Model 37s® with a serial number above 855,000 have interchangeable barrels (except for some Deerslayers), but often still require some custom fitting by our gunsmiths.

The thread pattern that we utilize on our interchangeable barrel field guns is the same pattern that was used by Ithaca in New York after 1963. However, Ithaca in New York used manufacturing methods that created differences between their firearms that made their barrels less than truly interchangeable. So, while some of our barrels may fit post-1963 guns off the shelf, others will require at least minor modifications to fit correctly. You may send your gun to us for the barrel head spacing to be checked and tested, and there is no additional charge for this service, or have your local gunsmith perform this fitting.

Try these guys, Ithaca specialists:

Diamond Gunsmithing

Les Hovencamp the owner of Diamond Gusnmithing was the head smith at Ithaca before they moved/bankrupted/closed the doors, whatever it was.

I've exchanged emails with him on this subject years ago, very helpful, extremely knowledgeable.