[Creeper]

Part 2

Neck Turning.
Based on the individual rifle, necks should be turned a little, a lot, or not at all.
The inside diameter of the chamber neck, the outside diameter of a loaded round and the total variance in wall thickness will be the determining factors. In any type of chamber, the reasons for turning the necks are so that the tension on the bullet can be made identical from case to case and that the bullet is presented concentric to the barrel throat.
If the case necks vary by .0005" or less, they have exceptional uniformity and typically would not require turning, for a standard chamber.
In a match type chamber it would be advisable to turn the necks only enough to obtain a .0001" case wall variation, assuming adequate room for neck expansion.
In a tight neck chamber, the necks must be turned not only to fit the chamber, but also to provide a small amount of clearance for the neck to expand and release the bullet upon firing.
My “tight neck” 6 PPC has a chamber neck diameter of .2620". A loaded round must be less than this dimension. The unturned wall thickness, times two, plus the bullet diameter add up to a loaded round neck diameter of .267". It will be necessary to turn from the neck wall a total of .003". This will be done in three steps. The first removing .0015", the second .001" and the last, a finishing cut of .0005". This will produce a loaded round diameter of .2610", allowing a minimum .001" total case neck expansion before contacting the chamber. Only a small amount of neck resizing, if any, will be required to reload these cases once turned.

A minimum specification chamber is desirable not only for accuracy, but for brass life as well. Sized brass, upon being fired will expand to the chamber dimensions then contract slightly.
A case, repeatedly full length resized, and used in a maximum specification chamber, may separate at the case head area or split along the body from the continuous expansion and compression process.
If the chamber is on the low side of the specification, when the case is resized, the amount of force applied to the case and the amount the brass must compress to return to it’s original unfired form is reduced. “Working” the brass as little as possible is what contributes to long case life.

Even in a SAAMI standard production rifle the clearance between the neck of a loaded round and the chamber neck can be substantial, although usually no more than .004" - .006"; occasionally it’s as much as .010". Quite a bit of room for the neck to expand, and this expansion coupled with repeated resizing of the neck will cause case necks to split.
If a deep hole gauge or I.D. micrometer is not available to measure the neck, try this; obtain a number of fired cases that have not been resized and measure the outside diameters of the necks. This will give an indication of the neck diameter in the rifles chamber. The case necks will measure .0005" to .002" smaller than the actual dimension in the barrel due to the brass’ ability to “spring back”, but it gives an indication of how much the case neck is expanding.

Should the difference in an unturned loaded round and the estimated chamber neck dimension be greater that .006" I recommend not turning the necks. Instead, try to find a brand of case with a thicker neck wall, which can be turned and still maintain a reasonable maximum clearance, or a case brand with no more than .0005" wall thickness difference.

Neck turning made easy.
Obtain a full length sizing die. Remove the I.D. sizing button and decapping pin from the die. Using a cull case, adjust the die according to manufacture’s instructions. Lubricate then size all the cases. This will compress the neck, move the high spots to the inside diameter and insure initial dimensional uniformity.
This next step is where the “expander body” previously mentioned comes into play. Insert the appropriate neck mandrel into the expander body and install it in the press.
Lubricate inside the neck of the cull case and adjust the expander body so that the full diameter of the mandrel just goes all the way past the base of the case neck when the press is at the top of it’s stroke.
Lube inside the case necks as well as the mandrel shaft, and then insert the mandrel into each case. Stroke the press a few times to expand the inside of the neck, until only slight resistance is felt.
Why do this? Well, the first step is to push the imperfections to the inside of the neck. The second step is to force the imperfections to the outside where they can be removed with the neck turning tool. This also insures that the case neck I.D. is perfectly round and a snug fit on the turning mandrel.

The most common neck turning tool consists of steel or aluminum body with a hole bored through to accept a mandrel; perpendicular to the mandrel is an adjustable cutting bit. In kit form, the tool will also come with a clamp to securely hold the case.

Begin by inserting the mandrel into the tool body. Second, retract the cutting bit so that it’s at least .250" away from the mandrel shaft. Using the same cull case since the beginning of this process, insert the case into the case clamp tool and “screw” it onto the mandrel shaft until it bottoms against the mandrel shoulder.
Adjust the position of the mandrel so that the cutting bit’s outside edge comes within .005" - .010" of where the case neck and shoulder angles intersect. This is done to avoid the possibility of cutting into the shoulder. If the bullets used will seat deeper than this junction then it will be necessary to cut slightly into the shoulder to prevent a ridge from forming in the neck I.D.
Tighten the mandrel locking screw. Measure the mandrel’s position in the tool body with a dial caliper and write it down along with the case brand for future reference.
Remove the case. Using a blade type feeler gauge and assuming that at least .001" of brass must be removed, start with a blade .001" less than the maximum wall thickness of the cases measured, place the feeler gauge between mandrel and cutter bit and adjust the bit toward the mandrel until you feel the slight drag of the blade between the two.
A “slight” drag should allow the feeler gauge to slide back and forth without being scarred or snagged by the cutting bit. If unsure, use a .001" thicker gauge. Brass is easy to remove from the case, but truly difficult to put back.

Lubricate the case necks, both inside and out. Lube the mandrel shaft as well. Insert the first case in the case holder and slide the case onto the mandrel, begin “screwing” the case down the mandrels shaft until it bottoms on the shoulder. Don’t feed the case into the cutter too quickly, about a 1/32nd to 1/16th of an inch per revolution. If the feed speed used is too quick it will leave “grooves” in the neck. Use a small paintbrush to remove excess brass chips from the mandrel, cutter bit and case. As with most of these tools, if there are a large number of cases to be turned, adaptors are available that will allow the use of a cordless screwdriver.

This first pass removes most of the “high spots” and this may be far enough. Should additional passes be required, don’t be in a hurry; remove no more that .001" of brass at a time. As the final desired dimension is approached, remove .0005" or less per pass. After neck turning all the cases, touch them up inside and out with the deburring tool. Clean the cases thoroughly.

Part 3 coming up...
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