Rebarreling and Home-Shop Machining

            I made a Gunsmith fit shroud to tighten up the rear of the bolt and hold it upward on my .300 Winchester Short Magnum Project Rifle. This is the normal position of the rear of the bolt when the rifle is cocked. After firing, there is some tendency for the bolt to drop which may affect accuracy and trigger pull. The shroud functions similar to the Crawford Engineering Shroud which I described below, but preserves the flat black finish on my Sendero Bolt.

            I mounted the Remington shroud in the milling machine vise whose fixed jaw I squared to the bed with an indicator mounted on the spindle. I used two blocks to set the flats on the bottom of the shroud even with the top surface of the vise. I used a wiggler with the pointed tip. I adjusted the tip to run true with the milling machine running and used the point and a magnifying glass to find a suitable reference. You can also use a ball end on the wiggler to locate the front and side of the shroud. The extra accuracy is probably not needed for this job.

            I chose a starting point where the front face of the shroud that normally bears up against the back of the bolt met the small diameter radius on the underside of the shroud. See photo 2. I then moved the part .110 inch right. This set the x axis which can be clamped for the rest of the job. I then moved the part .063 inch back to center drill with a 1/8 inch center drill (.110 inch) and drilled to size with a #31 (.120 inch) for a press fit on a slightly reduced 1/8 inch round stainless steel stock. See photo 3. The shroud has additional support for drilling from a shim stack. I reduced the 1/8 inch stock to .122-.123 by sanding it in the small drill press. The stock is not centered on the flats but is placed toward the center line of the shroud as this is where the part will bear on the receiver rails. I drilled the holes .3 inches deep. I hammered in a 2 inch piece of stainless with red Loctite on the pin and then hacksawed the pin off short. See photo 4. The lead padding will work the best if you sand the points of the vice face with your 4.5 in grinder or get replacement aluminum jaws for vise. The 1/8 inch stainless stock is available from the K&S Engineering hobby materials section in my hardware store and hobby shop.

Fitting

            If you use a feeler gauge to measure the clearance under the bolt you can estimate how long each of these rods will protrude from the bottom of the shroud. On this action they ended up with about .023 inch protrusion. See photo one for the finished part. File the rods down a little at a time until the bolt will open and close smoothly with only a slight play. Use a feeler gauge or shim stack of the desired thickness to have a stop and guide for the file. Put the feeler gauge adjacent to the pin and file until the file brings the pin down to the top of the feeler gauge. I have not tested this part at the range yet, but it seems to work OK otherwise.

            Note that I trued the threads in the bolt with the lathe and a ½ x13 thread per inch tap. This is described in the Crawford Engineering Shroud Topic below.

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