June 5, 2012

Excess Headspace in the 1903 and ’03A3 Springfield

GunReports.com shows how to excess headspace in the 1903 and ’03A3 Springfield rifles better than the way Granddad did it. If you have access to a lathe, use this method to correct excess headspace easily, without the need for an expensive chambering reamer.

Historically, gun people are quite conservative. Look at how long it took for the percussion lock to become accepted, not to mention the in-line percussion blackpowder rifle such as the Knight and others.

In order to correct excess headspace in the 1903 and ’03A3 Springfield, the textbook method has always been to set the barrel back one turn, or approximately 0.100 inch (03 barrel tenons have 10 square threads per inch), and then ream with a finishing reamer until a headspace gauge shows acceptable headspace. This procedure—the way Granddad did it—leaves unsightly gaps in the fore-end inletting, requires an expensive chambering reamer, and requires an educated guess as to how much metal to remove in order to rotate 360 degrees and arrive at the index mark with a nice crush fit.

Why not eliminate the feed cone with its extractor notch and proceed as we do with the Model ’93 to ’96 Mausers?

I believe the U.S. Army committee that designed the 1903 Springfield put that feed cone there just to get around some of Mauser’s patents. The angle is too steep to funnel the bullet into the chamber mouth, and it only looks like it might alleviate jams. It doesn’t strengthen the lockup, and machining it off doesn’t remove any threads, so the strength is still there.

American Gunsmith, Gunsmithing the Rifle

American Gunsmith, Gunsmithing the Rifle

With the barreled action clamped vertically in a vise, the go-gauge and shim disks are used to determine the amount of excess headspace.

A friend showed me a brand new rifle he had just purchased. It was made in England, and in all practical aspects the action was an exact replica of an ’03 Springfield, and “Hey! Guess what?” It had a flat, pre-98 Mauser-type breech face.

After seeing no feed cone in a new commercially made rifle, I decided to do a little research on my own. I took a junk ’03 barrel that I had used in some previous experiments and machined the feed cone off flush with the extractor recess notch. I assembled it to a spare ’03A3 action. Then I filled the magazine with an assortment of dummy rounds—220-grain round nose, 150-grain pointed softpoint, full-jacket military, and so forth—and they all fed flawlessly, even when the bolt was cycled with the action in various canted positions.

Now, let’s take a rifle with a bolt that closes easily on the no-go gauge (when using head-space gauges, always apply a light touch when closing the bolt) and go to work correcting the excess headspace. First, clamp the barreled action in a padded vise with the muzzle pointing up. Remove the extractor claw and striker assembly from the bolt, and place the bolt back in the receiver.

American Gunsmith, Gunsmithing the Rifle

American Gunsmith, Gunsmithing the Rifle

Materials needed for measuring headspace include gauges and disks cut from 0.002-inch brass shim stock. The micrometer is helpful, but optional.

Now make about a half-dozen small disks out of 0.002-inch brass shim stock. These disks should be the same diameter as the head of a .30-06 shell. Place one 0.002-inch shim and the go-gauge on the bolt face and gently close. Keep adding shims and repeating the process until the bolt doesn’t close. Now add up the 0.002-inch shims or mike them. This will tell you the total space between the go-gauge and the bolt face. Make a note of this measurement.

Now remove the barrel from the receiver with a pressure yoke barrel vise (easy to make or buy from Brownells), then set the barrel up in a lathe with a steadyrest. Face off the feed cone even with the bottom of the extractor notch. Then face off the amount you measured with the shim brass disks, minus about 0.004 inch which is allowed for variation in factory- and hand-loaded shells. Remove the same amount from the shoulder.

Screw the barrel and receiver back together and check your work with several brands of factory cartridges (with the striker still removed). If you were over zealous and removed too much metal, it’s all right to install a thin steel shim between the shoulder and receiver ring. (Don’t try the latter on a Model ’98 Mauser.) If you’re happy with the way it chambers several brands of factory shells, the job is finished and you can stamp a new index mark on the barrel.

American Gunsmith, Gunsmithing the Rifle

American Gunsmith, Gunsmithing the Rifle

These Springfield barrels show the feed cone (left) and the feed cone removed (right). The author maintains that it does no harm to remove the feed cone when correcting excess headspace in ’03 and ’03A3 Springfields.

Obviously, you wouldn’t use this method of breeching on a custom barrel with a front sight ramp, or one with a rib milled integrally with the barrel. You would remove 0.100 inch from the barrel shoulder and the feed cone to bring the barrel 360 degrees back to the index mark. Then ream the chamber enough to restore proper headspace.

I don’t think I would flat breech a 1917 Enfield, because it would remove part of the thread and maybe weaken it, but the very similar Pattern 14 Enfield, chambering the rimmed British .303, has a flat breech face. I’ve had no experience using this technique on other rifles with funnel-shaped breeches—the early Model 70s and Savage Models 40 and 45, for example—so I cannot offer comments or advice on these.