Reply With QuoteIdealy, you would want to use a FL sizer and then use an expanding mandrel to expand the neck to the right size to fit the neck turning mandrel. Usually the expanding mandrel is only .0005 larger than the turning mandrel.
Just ordered the K&M setup from Precision Reloading. I'm new to neck turning. Should I collet size prior to running the case into the expander die? Checking my necks on an RCBS CaseMaster, they seemed to be only a few thousands different around the neck.
Vietnam Vet, Jun 66 - Dec 67
Idealy, you would want to use a FL sizer and then use an expanding mandrel to expand the neck to the right size to fit the neck turning mandrel. Usually the expanding mandrel is only .0005 larger than the turning mandrel.
You'll want the neck larger, maybe .001" at mostover the turning mandrel diameter which generally requires expanding them to the correct ID. The fit must allow the case to turn, but without being sloppy loose if you want reasonably concentric necks. Too loose and you'll have variations in the wall thickness, too tight, its tough rotating them and the mandrel may heat up and change dimensions. It all depends how accurate you want them.
When I use a hand turner I'll size the necks with a FL or bushing die then use an expander to open them the correct ID for the turning mandrel. That pushes the thicker portion of the brass to the outside of the neck to be turned off.
For lubricant I still use the old 50/50 mixture of Mobil 1 and STP applied to the inside of the neck with a Q-Tip Yeah, its somewhat messy, but its slippy and easily cleaned off with lacquer thinner or denatured alcohol.
Another suggestion. Depending how much you need to remove, make multiple cuts instead of one. For example, if the necks are .017" and your turning them to .012", first take maybe two .002"cuts then a final .001". Even if I'm turning them in my lathe I'll make multiple passes.
Its a little different if I'm doing them on the lathe, but the same idea. I'll chuck mandrel just slightly larger than the neck ID then push the case over it which expands it, pushes the thicker brass to the outside and provides the tension to rotate the cartridge, it basically does everything in one step.
Bill
Tom,
Bill covered it well. I usually F/L size without the expander ball to make sure the neck OD is as concentric as it can be. That also establishes a crisp neck/shoulder junction (important). I don't think you'd get this with neck sizing with a collet die. Then i run them over the expander mandrel (lubed inside neck with Imperial wax) to expand them. You really want the neck to turn tight on the turner mandrel but not so tight that it galls the brass. Adjust the cutter relative to the case neck length so that it just barely nicks the shoulder at the neck/shoulder junction.
Try it on a few cases - you'll get the hang of it quickly. Works much better to cut in increments than to remove more than about a thousandth at at time. I usually turn 10 then give my hands a break by measuring neck wall thickness with a tubing mike for a few minutes. And you will probably have some of the cases that just refuse to get even, regardless of what you do. If I can take 4 measurements around the neck and have them within a half a thousanth, I call it good.
Elkbane
Thanks guys, that clears up a lot of questions. I guess I'll have to invest in a good full length die (Forster/Redding) as my Lee die really screwed up the case necks throwing them out of wack by .005 or more. All I have at the moment is the collet die and a Redding neck die.
Vietnam Vet, Jun 66 - Dec 67
K&M sells a expander die and the correct sized mandrels for their turning mandrels. http://www.kmshooting.com/catalog/ex..._complete.htmlOriginally Posted by GaCop
It probably easier, cheaper and will save the old nerves in the long run to purchase the complete tool so you don't need to fight trying to get matching sized parts especially if your going to turn brass for other calibers ( diameters) in the future.
Bill
Very good advice, did just that about 3-4 weeks ago, and it sure did make it easier, went ahead and ordered both .20 and .224 mandrels for the neck turn tool and the expander die.
Yes, I ordered the complete setup too in 7mm.
Vietnam Vet, Jun 66 - Dec 67
My K&M setup arrived yesterday and my Redding full length die, boy they ship fast! I'll be playing with it today giving it a test run on some 7X57 brass so I don't screw up my Nosler 280 AI.
Vietnam Vet, Jun 66 - Dec 67
GaCop-- I read through all the replies rather quickly and didn't see anyone suggest that you trim all you casings to EXACTLY the same length. I use the K&M jack to get the mandrel set to the proper height so when I turn the casings, the cutter will make a slight cut onto the shoulder. If you don't have casings all the same length, then you either get deep into the shoulder or too shallow or somewhere in between. Don't spin the casings too fast or you'll be flirting with causing the mandrel and the casing neck to heat up. Also, it doesn't hurt to put a little lubricant on the neck of the casing and also always lube the inside of the neck and the length of the mandrel. I do that before every casing.
Catch Ya L8R--Silverfox
+1 yep, I forgot to mention that part
Not a problem. I keep my brass trimmed. I always trim to the shortest case length. So far. all my Nosler AI cases are WAY under the max length by about .030". My shortest case measured 3.510" so I've trimmed all my cases to that length.
Vietnam Vet, Jun 66 - Dec 67
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