Remington M700 Recoil Lug Alignment Jig: Using a special recoil lug alignment jig while installing a barrel on a Remington Model 700 rifle series receiver eliminates the guess work in proper barrel installation. Here's how to make and use one.
As an inventor I never have thrown much away that could be used in the development of a new idea. So as I mulled around in my mind for the parts and method of manufacture for a lug alignment jig, I visualized a part made from a short section of common steel water pipe split lengthwise down the axial center. I measured the Remington Model 700 receiver to be 1.360" and the inside diameter of a water pipe to be the same diameter. How often are our chances of randomly finding such a fit? So, with pipe wall thickness at an ideal 0.131" it was all systems go.
In operation, the half circle of water pipe would fit over the rifle receiver and a notch the same width as the recoil lug would align the parts. The jig would be attached to the receiver with a short 1/4-28 bolt at the front guard screw hole. I held the section of pipe in the lathe chuck and removed any outside imperfections in the section of pipe used.
The 1.660" length of pipe was marked and split lengthwise with a band saw and the parts were cleaned, deburred, and brushed with a stiff wire wheel. Each section of pipe, as split, makes two of the jigs, so while I was at it I conveniently made one for a fellow who also does gunsmith work.
Finishing The Parts
With the jig parts fitted to size, marking and milling the recoil lug slot was next in order. Here I removed the stock from a Model 700 Remington rifle and placed the action upside down to align the part over the receiver with one end butting against the recoil lug. Held squarely into position, I carefully scribed marks at the end of the jig to indicate precisely where to mill out the slot. Then, with the part held in the milling machine vise, the slot was milled out the width of the recoil lug. The whole project wasn't going to take much time.
A hole for the recoil alignment jig was then marked and drilled. Marking this hole should be done carefully from inside the receiver screw hole with the jig squarely in place. The short 1/4-28 bolt should then enter the hole freely to hold the part squarely in position.
Using The Jig
While being used, the recoil lug alignment jig allows the recoil lug to be self-centered as the barrel is screwed onto the action. It is not necessary to have the jig in position while removing the barrel from the action.
I always place a recoil lug in the same front-to-rear position as it is returned to the action. This tends to place any variance in tolerance to the same position, however minor this may be. I have measured the laterally opposing wall thickness of various recoil lugs and there can, indeed, be a difference side-to-side at the ring wall. Subsequent group tests with the recoil lug reversed showed a variance in bullet point of impact. This shows us how important barrel shoulder to receiver contact really is in altering the joint axial preload. Axial preload or barrel joint torque can be altered in a few ways. Chief among these are barrel-to-receiver shoulder smoothness, quality and number of threads per inch, barrel thread diameter and type, and amount of barrel thread lubricant used.
I work with many switch barrel rifles where the scoped action remains in the stock as the barrel is held in my special padded vise jaws during removal and re-installation. Here I use an action wrench and torque bar as the recoil lug is self-aligning, held in a well-bedded position.
In my quest for a special part or tool needed to perform a certain operation in my work I often just let things happen. In the development of my recoil lug alignment jig it was later pointed out to me that Brownells does indeed offer such a part (#488-004-700 WB) at $54.99. Seems my cognition was right on as this part looks much the same.
Anyway, make one or buy one. You should have one if you want to attach that barrel to the action correctly.
by Norman E. Johnson
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|Author:||Johnson, Norman E.|
|Date:||Apr 1, 2019|
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