6PPC Neck Turning
From the June, 2000 issue of NBRSA News
Like most benchrest shooters I don’t like to spend a lot of time preparing 6 PPC cases for match shooting. I’d rather be shooting groups with the cases than working on a new batch of brass. But the job isn’t near so time consuming as it once was for me. When I started shooting in registered benchrest matches in 1976, I purchased a neck turning tool made by Paul Marquardt. Paul is gone now but I still have and use the neat little tool that he developed. In those days we held the case in a little clothespin type clamp which was then held in a vise. The Wingnut type turning tool was rotated by hand and the brass flowed off of the neck with each twist of the tool. It was a long and hand tiring process. But it worked.
Now though, I use a milling machine to turn case necks, not just for the PPC size cases either, I’ve done the same with 50 BMG brass. It so happens that a PPC case will slip into a 7/16″ diameter collet just right and I use the milling machine spindle to turn the brass. The neck turning tool is held in the vise. The trick is to be sure the tool is held squarely in the vise and that the collet is centered directly over the tool mandrel. With other case diameters that don’t fit neatly into a standard diameter collet, I use a Jacobs 3-jaw chuck to hold the case.
The machine I use has a variable speed spindle drive and I wondered at first if the low RPM range of the direct drive, 500 RPM, would be too fast. It proved not to be though and with the application of a little tap cutting fluid, like Cool Tool, a very nice uniform cut is made on the case neck in just a few seconds. This particular machine also has an air-activated collet-closer and so the whole operation is very quick. I recently turned 50 6 PPC cases in 30 minutes or so.
My 6 PPC reamer has a .261″ diameter neck and I turn my necks to a thickness of .0085″ per side. This leaves me about .001″ clearence between a loaded round and the chamber. Some shooters like a closer fit but this diameter has worked well for me.
I think the quality and consistency of the turned necks is better than when I did them by hand. The high speed, uninterupted turning, along with the cutting fluid, produces a very nice finish. Also, with the case centered directly over the mandrel, there is no side deflection of the case as there is when turning by hand. Every neck is the same size as the previous one. I spot check the neck thickness with a tube micrometer. Uniformity is one of the keys to shooting little groups. And little groups are what benchrest shooting is all about.