Neck turning


Ruger GP100 fan
December 9, 2010, 06:22 PM
A question I posted on another thread went unanswered,perhaps because it was a bit off-topic. It has to do with neck turning. I've noticed that the amount of pressure needed to seat a bullet in my Winchester brass varies quite a bit from case to case. Each is re-sized with a standard FL RCBS die with an unaltered ball on the decapping stem. My question was whether or not the brass should be turned empty or with a bullet seated in it,or if turning the brass at all has advantages. Also,someone posted here or perhaps on another forum that reducing the size of the ball prevents the brass from being overworked,but doesn't the bullet just do the same thing when seated? What's the advantage?
I have begun weighing the brass and selecting groups for target shooting by their weight,but have yet to fire any of these. I've noticed quite a variation in weights. These pieces of brass have been fired 6 times and show no signs of damage. Even the primer pockets are as snug as new brass as best I can recall.

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December 9, 2010, 07:46 PM
neck turning- brass is turned empty.- You have to turn necks and test to know if it helps accuracy.- The size of the ball is ok @ .002" smaller than bullet diameter.

December 9, 2010, 08:07 PM
Yep, it must be empty to go over a mandrel for neck turning.

December 9, 2010, 09:34 PM
Neck turning is for making the neck thickness uniform around the case neck and to make the necks uniform from case to case.

A bushing resizing die with the correct size bushing and no expander ball would work the brass the least. But best neck tension results are obtained with uniform neck thicknesses.

As others have said, case necks are trimmed with the case empty, at least with every neck trimming tool that I am aware of.

December 9, 2010, 10:20 PM
I would look into a bushing style neck die.

There are a few variations on this. Load a round in your brass, measure the outside diameter and subtract .001 or .002. That will give you the size bushing that will work well for you. I have had very good luck using these style dies. The lee collet style works well too.

As to neck turning, it depends on the brass. I use it when I am making 260 rem brass from 7mm08. However, I do not usually bother with it in typical loads. If you run good brass like lapua, then the cases should be pretty consistent.

The best I can say is try it and see. I had good results when using rem brass, but very little difference on Winchester or lapua.

Ruger GP100 fan
December 10, 2010, 06:55 PM
redbullitt "I had good results when using rem brass, but very little difference on Winchester or lapua."

Are you saying that Win. is as good as Lapua in every way,because there is a huge price difference. For 22-250 I can get 100 pieces of Win. for <$40.

Since I load for just 1 caliber and not many rounds at that,I'm beginning to wonder is annealing is such a big deal in my case. A good friend suggested that I buy the best brass I can afford,use it until the necks/pockets begin to fail,then throw them away and start over with new brass,because annealing for such small numbers of brass would not be cheaper once I factor in gas and accessories.

December 10, 2010, 08:40 PM
Winchester is good brass, but not as good as Lapua in every way.

December 11, 2010, 08:03 AM
Winchester is good brass, but not as good as Lapua in every way.



December 12, 2010, 12:52 AM
My neck turning procedure (your mileage may vary):

#1 back off a full length or neck sizing die so it does NOT resize the case! Leave the expanding ball in without a decapping pin. This will expand the neck to a uniform diameter and ensure it's concentric.


#2 Measure the mandrel diameter on your neck turning tool (this is the part that goes in the mouth of the case...)

COMPARE THIS MEASUREMENT TO STEP #1. The mandrel should be the exact same diameter of the sized case mouth, or no greater than .001 smaller than the inside diameter of the sized case mouth.

#3 measure the neck wall thickness of several sample sized cases. Take the outside diameter, less the inside diameter, divide by two. Compare this with a direct measurement to double check.

Unless you have a tight-neck chambered rifle, you'll want to remove a minimum of material. I normally choose to remove .002 from stock brass in a normal factory chamber. In a tight-necked chambered rifle, you will need to check with the barrel maker to find what you should turn to for a final outer diameter.

An example: I'm loading 308. My el-cheapo sacrificial RCBS 308 neck sizing die is backed off so that it ONLY functions as a neck expander. I expand some case necks. The average inside diameter is .305. The outside diameter is .330. My case wall thickness is .012 when measured directly (which matches the 0.0125 when mathematically calculated). My mandrel on my neck turner is .305. It's a tight fit to get the casings on it. When I turn the necks I pick a target thickness of .011 - removing 1.5 thou from the neck.

#4 Neck turn the casings.

#5 Size the casings with a bushing-capable neck sizing die. You MUST use a bushing die if you neck size because they don't touch the inside of the case neck! At this point you are pushing a case BACK to a dimension. Normal sizing dies expand on the retraction.

Why? Because at this point you've cut each cases wall thickness to a precise amount.

What size bushing do you get? You know the bullet diameter, and wall thickness, so subtract .002 and you got it.

Example: the afforementioned 308. I finish neck turning, and run the 308 through the Redding bushing die to finalize the neck. I pick a bushing diameter of .308+.011+.011-.002= 0.328.

This now gives me an absolute internal diameter of .306, and that precious "same exact amount of bullet tension in every case" that reduces velocity deviation.

PRIOR to seating bullets, it's a good idea to hand-chamfer the inside of the case neck (not mechanically!) to make sure they seat without "shaving" the sides of the bullet. I do this while I'm waiting for the RCBS electronic powder tosser to count out a charge.

#6 Seat your bullets, taking care to make the initial alignment as close as possible. Use a high grade seating die - Redding makes fine ones, so does Forster.

Done in this fashion, EVERY bullet you seat in a cartridge will have the exact same neck tension.

December 12, 2010, 12:57 AM
PS; with neck turning, primer pocket uniforming, and flash hole deburring, with an electronic scale capable of .1 grains (RCBS), I'm able to obtain a maximum velocity spread in my 300 Win Mag of 15fps - vertical stringing isn't even noticeable at 450 yards. I've heard of guys with 300WM's getting below 8fps velocity difference by using high-end scales capable of .01 grain resolution.

However, if you don't follow a sound procedure for neck turning, you're wasting your time. The idea is to get the exact same tension on each bullet, which means certain things have to happen in certain order...

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