Rebarreling and Home-Shop Machining

Chambering

The chambering went really well. I polished the chamber, which was very smooth already, with 1500 grit. Only took a minute. I used the chambering procedure described in "Precision Rebarreling" so will not go into detail here. I got a complete fresh cut that removed all the factory chamber. Targets to come. I sold the 1 inch scope that was on the rifle, so I have to wait a bit for some new rings. They will be Leopold QR with two piece bases. I think that the esthetics on this particular rifle will be better than with the Farrel Rings and one piece base that I had mounted previously. The scope will be a 30 mm tube Leupold Mark IV 4.5 x 14 M1 tactical scope.

I mounted the barrel with a blue Loctite paste that I have come to favor. It comes in a chapstick like tube dispenser. It stays where you put it.

Matching an Existing Thread

I had to add some threads after trimming the barrel extension by 7/16 inch. This is not an easy task on a small lathe due to flex in the feed screw, feedscrew supports and carriage. The procedure is this.

Put the lathe in gear and feed left under power with the bit off the work. Park the bit by your existing threads. Lock the carriage. Now adjust the bit with your compound rest feed wheel and cross-slide feedwheel until it fits nicely in the existing thread groove at full depth. Use a magnifying glass with white paper under the work to reflect light. You can get it adjusted really well.

Now the problem is, the bit is not taking a cut. When you cut the new threads flex in the machine will offset the new threads slightly toward the tailstock. (away from cutting pressure). You are not going to get an exact match.

Do not recut the original threads, this will only makethem sloppy. Instead cut thenew threads until the receiver will just thread on. They will be more pointed that the existing threads. The thread can be made tight even though the diameter in the center of the thread profile will be smaller than stock.

I cut this thread with a straight in feed which is the habit at Shoptask. I thought this might reduce the offset. It did not. Instead it just made a more raggedy looking thread than what I have been getting in steel using the compound rest. It works fine in brass this way as there is less of a requirement for high rigidity in the lathe. I cleaned up the thread with the two tiny files. The receiver threads on tight the whole length of new thread (I need a 1 foot wooden lever). This will help my lockup to remain complete over the whole barrel extension. I will still use blue Loctite. Next time I will use the compound rest and try moving the bit to the left about .003 inches before I start the new threads. I am satisfied with the fit this time though.

Winchester Model 70 Coyote (WSM action) in .308 Part II

Barrel Work

              I mounted the barrel and aligned it radially and axially with the methods shown in Precision Rebarreling. After this I had to decide how much to shorten the barrel. Close inspection of the factory chamber showed that it was not as crooked as I first thought. This was good. It would allow me to put in a new chamber with out overly shortening the barrel. The .308 case does not have much body taper. It might take quite a length of cut with the chamber reamer before it will remove all of the old chamber. The barrel threads are 16 thread per inch. This means that each thread is 1/16 inch (1/ Number of Threads per inch). To keep the factory lettering aligned you would need to shorten the barrel a whole number of threads. I decided 7 threads or 7/16 inch (.4375 inch) would be the best compromise to insure cutting a completely new chamber and neck and also to leave enoughthreads on the end of the barrel for a good barrel to receiver lockup. I will again use blue Loctite as there is no way to expand the original thread diameter. (If I were cutting a new blank I would make the threads oversize to fit the receiver and use a custom thread profile that I describe in the book.) The new thread will have an interruption in the middle which will cause little problem as the thread is way oversize for the thrust involved in firing the cartridge. ( I have calculated this)

Parting

I used a high speed steel parting tool with coolant. The parting tool holders (flex slot) is welded solid for added rigidity. I got fairly continuous chips and fed the tool inward by hand. See photos 1 and 2. There is a slight 60 degree center in the breech end of the chamber to help feeding or for production reasons. I plan to put a similar center in the new end.

Coolant Nozzle from Grizzly

After sitting with coolant for a few months the nozzles leaked this time I used them. I was able to tighten the valves to cure most of the leakage. Some of the leakage happens in the plastic of the nozzle itself. This causes little problem in that it is always over the main pan. I am using a gold coffee filter in the pump itself to take out fines from the return oil that tend to clog my final after pump filter. Seems to work OK at this point.

Breech end Chamfer

The factory Chamfer on the breech end was not 30 degree (not a 60 degree center). I put a 45 degree chamfer on this end of the barrel to match the factory chamfer. I used a small boring bar on the compound rest to get my 45 degree angle. I fed the bit by hand with the compound rest feed wheel. I adjusted depth of cut with the carriage feed wheel.

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