Rebarreling and Home-Shop Machining

Renecking a Full Length Sizing Die

             I have made 3 of these renecked Lee dies now, one in 30/06; and two in Winchester Short Magnum, one with a .336 neck for unturned brass and one with a .335 inch neck for turned brass. The stock Lee neck is .325 inches which really works the brass hard. The Lee Pacesetter two die set is $20 so this is practical. The Lee die also has an expander mandrel that is held centered by a collet. (I have bent my Redding decapper rod twice already sizing only a few cases.) I brought this topic back up as I have new photos with my homebuilt Dewalt tool Post Grinder and new results to report. Previously I used a homade Dremel tool post grinder to make a Shoulder Bump Die.

            It is helpful when resizing rifle cases if you do not overly work the neck. This produces straighter cases and also does not work harden the brass as fast so the necks stay soft through more firings. One way to work the brass less is to use a bushing style full length or neck size die. Another way is to have a full length die renecked by the manufacturer(Forster offers this service on a new die) or to do this yourself.

            I am starting to prefer Precision grinding the interior neck portion of the die as described below as I get better results than a bushing style die, especially with brass fired in a standard neck size chamber. I imagine that the bushing dies have a floating bushing because the die was reamed from the threaded end. The hole for the bushing has to be made from the other side of the die. It is a difficult machining operation to have these two holes meet exactly concentric on a production basis, hence the floating bushing to allow it to self align. Self alignment with a bushing die is not as good as forced alignment in my tests with a renecked die.

Using a 4-Jaw Chuck

            I chucked the Lee Full length die in a four-jaw chuck with the threads supported by a brass strip. I indicated in the neck with a dial indicator and a hole attachment. Adjust out any radial runout with the four-jaw chuck. I moved the indicator along the length of the neck and I was still dialed in, <.0001 inch radial runout, also < .0001 inch axial misalignment. Great. If you have some axial misalignment you can tap the die around a little with a brass punch and small hammer. This will reseat it in the brass strip that is on the sharp threads. I tried previously to chuck on the outside of the smooth cylindrical portion of the die (the non threaded portion of the die). This did not work as well. I ground the inside of the neck, with the Dewalt Tool Post Grinder that I made, until it was .0005 inch undersize from the desired bushing I normally use. I will polish the rest out using a brass rod that has a slit cut with a .010 inch thick X-acto saw. I can insert a strip of fine wet or dry sand paper and spin the rod with the Dremmel and achieve a mirror finish on the interior of the bore. A little extra attention from the threaded end of the die will radius and smooth out the entry to the neck. If you like to full length size this is a way to breath new life into an old die.

Aligning the Grinder & Measuring the Bore, Finished Dimensions .300WSM

            With this shape of stone it is important to prevent a belled condition to the bore. I used a dial indicator on the shaft of the grinder to put the left side of the stone a couple of thousandths closer to the operator than the right edge. I made the cut on the near side of the die. This allowed the cutting portion of the stone to pass more completely off the left side of the neck as it sits in the lathe. I checked the inside diameter with a dial caliper to start with. Usea light touch for this partial contact and with practice you can read it to .0001. Then I used an inexpensive spring loaded bore gauge and a Vernier micrometer. The bore gauge allows you to feel for any taper. See photo 3. Experiment with these tools on a steel bushing from a bushing die. The titanium nitride coated bushing, I believe, run about .001 inch small from the coating.

            On this .300 WSM die the last measurement with the bore gauge in photo 5 was .3348. I will polish it a bit with the homade flap sander and 1500 grit paper to take out the last little bit and make it .335 ID. The WSM brass is fairly hard to withstand the high pressure and requires a slightly smaller neck size in the die than my other calibes to achieve good bullet to case grip. The finished round with turned cases measures .338 inch in diameter around the neck for my .340 inch neck chamber..

Using a 3-Jaw Chuck

            Note that I also ground one of these Lee full length dies in the three-jaw chuck. I chucked the die on the threaded end with a brass strip cushion. I tapped the die into alighment with a brass punch and a small hammer. This causes the threads of the die to bite into the brass a little more on the side opposite the blows. I achieved good alignment. This worked well and was sufficiently rigid as the grinder does not put much force on the die.  I used this die for the .300 WSM test below.

30/06 Sizing Results

            I sized 9 oversize Lapua cases with unturned necks that were fired in a standard chamber Remington 30/06 rifle with the renecked Lee die. The runouts were 1 at .0015 inch one at .0005 inch and the rest .001 inch. This is outstanding for cases fired in a standard chamber. Before this modification runouts tended to be .002-.006 inch, mostly .004 due to the large amount that the necks were working. The shoulder was bumped back .0005 inch with the setting of the press that I used. The neck of the die ended up right at .334 inch after sanding right as intended. Lucky here. It needs to be bit smaller for brass with thin necks. The Lapua brass is a little thicker than even Federal Brass.

.300 WSM Sizing Results

            I sized 19 unturned Norma .300 WSM brass cases that were shot in my tight necked .300 WSM project rifle and full length sized them with a Lee die that was renecked to .336 inch. 6 cases had runouts less than .0005 inch, 12 less than .001, and only 1 less than .0015.

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