Rebarreling the Remington Model 504 .22 LR

The Model 504 Remington barrel is not threaded into the receiver. Instead, a receiver clamp screw and side-positioned set screw are used to position and lock the barrel in place. Cartridge headspacing is accomplished by allowing the breechface of the barrel to be moved rearward up to the recessed bolt face and then locked in place. The rimfire cartridge head is not recessed into the barrel, but into the bolt face. A pair of angled extractor grooves are cut at the sides of the barrel adjacent to the chamber mouth.

Fitting the Barrel to the Receiver For the job detailed in this article, I chose a Lilja cision Rifle Barrels Plains, MT 59859) o afted aftermarket barrel for the Remington Model 504 rifle. The procedure for fitting the barrel Top 22 LR sports a very strong action, shown here with an aftermarket stainless-steel barrel installed. The scope seen here is a 4.5-14 Sightron with a Leupold mounting system.

Bottom The reamer has removable pilots to fit various barrels with precision. to the receiver involves careful lathe and milling work in duplicating the factory specifications of the barrel that’s being removed. Barrel removal is accomplished by releasing the main clamp bolt and side-positioned setscrew. At this point, careful measurements are taken of the factory barrel and recorded. The new barrel blank is positioned in the lathe and centered in preparation for turning to the desired size.

The normal barrel breech is turned from its normal larger diameter to a size that will enter the short recess at the front of the receiver ring. This is 1 inch in diameter on the Remington factory barrel. With the barrel turned to 1.016 inches, I placed it in the center rest in preparation for facing the breech end and turning the shank to factory specifications. The breech-shank diameter is turned to 0.672 inch for a length of 0.935 inch.

Following this, an annular step, 0.035 inch deep to a diameter of 0.605 inch, is cut at the extreme breech end of the barrel. This step protrudes through a 0.605-inch-diameter hole at the juncture where the barrel breech surface meets the boltface. Actually this is a unique way of

establishing cartridge headspace as it affords some take-up for any wear sustained at the locking lug surface. With the barrel shank turned as described, it cannot be tested for fit until a slot is cut into the underside of the barrel to mate with a small, shallow positioning stud located on the inner, lower surface of the receiver. This shallow slot is cut 1/16 inch wide, 0.055 inch deep, to a length of 0.55 inch beginning at the barrel breech face.

The barrel now can be tested for fit, but first, the extractors should be removed, being careful not to lose the springs and plungers. Also, be sure each extractor assembly is replaced as removed, because there are leftand right-side extractor assemblies. The extractors simply swing out with a firm outward pull with the fingers, and are reinstalled by pushing them firmly into position compressing the plunger and spring.

When testing for barrel fit, be sure the clamp screw is relaxed and the receiver set Slots are cut very close to the chamber mouth. The 0.064-inch-wide slot used in the factory barrel is replaced by a narrower 0.042-inch slot on the replacement barrel. screw is turned out clear of the inner surface of the receiver. With the rifle held vertically (muzzle up) and with the bolt closed, allow the barrel shank to rest against the bolt.

Opening the bolt would allow the barrel to fall a few thousandths farther into the receiver, which is normal and a good test of barrel clearance. Following this test, close the bolt again to push the barrel to the correct headspace position against the sur-

A common shallow recess makes a good crown for the .22 LR. This is the "key" to this barrel-changing system. face of the barrel. Then put moderate torque on the barrel-clamp screw. The receiver set screw is then torqued lightly against the barrel, enough to make a discernible mark. At this stage, I release both the barrel clamp and receiver set screw and examine the barrel shank for the set-screw mark. Too heavy a depression could raise the metal enough to cause a bind in removing the barrel.

Now repeat the procedure outlined in the last paragraph and again examine the set-screw mark left by the receiver set screw. If only one setscrew mark appears, all is well. I then place the barrel in a drill vise and carefully center a center drill over the set-screw mark, and actually make a shallow depression there. This depression should be just deep enough for the receiver set screw to enter and position the barrel. Try it, following the procedure in the two preceding paragraphs.

Before trying the barrel for its final fit, however, I use a rounded machinist’s file to remove any burrs around the set-screw hole. The barrel should now fit with correct headspace as both the receiver screw and clamp screw are tightened. If the bolt seems to close correctly as the receiver set-screw is lightly torqued, all is well. If the torqued receiver screw produces bolt bind, you have some axial preload which means the screw hole should be brought a thousandth or two away from the breechface of the barrel.

What you’re trying to accomplish here is to have the receiver set screw serve as a double check of the headspace setting, not as a major means of locking the barrel in place. Though .22 LR rim thickness will vary from brand to brand, the average rim thickness on a number of cases I tested was 0.0414 inch. The bolt-face case-rim recess on the Remington Model 504 is .0425 inch, which translates to about 0.001 inch headspace for the average .22 LR rimfire cartridge.

Making the Chamber The chamber can be reamed to depth any time after the final barrel-breech surface is faced. The Model 504 chamber is not recessed into the barrel and the chamber is cut to recommended depth according to the reamer specifications. I used a Manson match reamrecision Reamers, and Blanc, MI to make the chamb movable pilots for an exact bore fit. Take plenty of time in reaming the chamber and be sure the reamer is not loading up with chips.

The Manson match chamber that I used cuts a perfectly centered chamber with the correct size removable pilot. Making the Extractor Grooves Cutting the extractor grooves on the barrel is an easy task. I used a 1/8-inch x 1/2-inch-diameter keyway cutter, with the barrel held firmly and squarely in a milling-machine vise. Using the barrel-locating slot as a guide, be sure the slot is in the true, upward position and perfectly square to the vise jaws.

Carefully advance the cutter into the edge of the breechface of the barrel until the cut is within a thousandth or so of the chamber rim. Then cut the other side at true barrel/ chamber center. To enhance extraction and ejection, I smoothed off the roughened edges of both the right-hand side ejector and the cartridge-retaining ejector. This produces a smoother ejection of the fired case as it hits the ejector setup. Conclusion The Remington Model 504 is a wellmade rifle, capable of excellent accuracy.

Adding custom barrels, however, can make this rifle much more versatile. The gunsmithing for this task is relatively simple and straightforward, requiring only the basic shop tools and some careful attention to detail. I