I tried neck turning my 300 WM norma brass, before the mandrel it was .005-.001" runout on the neck, after the mandrel .004-.005", neck turned .004" run out. Am I using it wrong or does this happen to you?
K&M neck turning mandrel causing run out.. Please help
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Define "runout". Tough to tell what's going on unless you're more specific. Turning necks should not do anything to runout except to reduce it by the amount that the uneven neck thickness caused.
Well I tested it right after I turned it (.004-.005"), than put it through a redding type S die, and that increased by .001-.002! I'm not going to use that and going to use either a honed Forster or lee collet die. I'm testing runout on Sinclair runout gauge. I would like to be finished neck turning and resize it and have less than .001" not .006"! I have tested everything and can tell for certain the K&M mandrel and redding type S (no expander/ or with expander) are causing me neck run out, which than translate to bullet runout in my finished round, which I feel like is really killing me.
That's what I would have figured, but the expander mandrel is causing me .004" runout and the only way to possibly fix that is to fire form it, which to me is unexeptable. I would like runout to stay the same as the new case (.001") or better.
That's odd. The mandrel doesn't really need to expand anything. I don't use a k&M, but my neck turner's mandrels (a sinclair model) are a zero-clearance fit (or very close to it) with new brass. Maybe your mandrel is too big. When you turn the necks, there shouldn't be any stress on the case - just the cutter doing it's work. With a little lube (I use some stuff meant for bike chains), the mandrel shouldn't provide more than light frictional resistance. If you have to use enough force to move brass to get the case on the mandrel, then that's your problem.
Are you using power? How are you holding the case? It's possible your'e torquing it while you trun the neck. Try it by carefully by hand and see if that doesn't help.
Are you using power? How are you holding the case? It's possible your'e torquing it while you trun the neck. Try it by carefully by hand and see if that doesn't help.
I knew I should have got the Sinclair! Haha the mandrel is certainly sizing my new norma brass. After is been opened up I can almost slip the .308 bullet in with no ease. It is a good for on the pilot however, and I would say I'm not torquing it because I measured the run out right after expanding it and there was run out. I was thinking for my next batch of brass to fire the cases and than try and set my lee collet die the same ID as the neck turning pilot and do it that way, what do you think?
What's also weird is the mandrel has no way of securing the case, the mandrel just sticks below the die threads. It looks like sinclaires supports the case?
I don't use a expander die unless I'm necking up brass (from 6BR to 30BR, for example). In that case, you're going to have to fire form to get it just right anyhow, so I don't worry about runout. My Sinclair expander is really old, but it just holds the mandrel - the case is unsupported.
When neck turning an off the shelf caliber, I take a brand new case and turn it right out of the box. The mandrel on the turner (which might be a slightly different size than the one for the expander die) should be a tight slip fit. I do this by hand, although I don't think that matters. Are you saying you cannot turn the brass without first expanding it?
In any case, I wouldn't worry about runout until the brass has been fired, especially if your'e dicking around with necking up/down. What you should see is a consistent neck thickness all the way around the neck. Within a tenth or two (you'll need a tube mic to measure this accurately).
When neck turning an off the shelf caliber, I take a brand new case and turn it right out of the box. The mandrel on the turner (which might be a slightly different size than the one for the expander die) should be a tight slip fit. I do this by hand, although I don't think that matters. Are you saying you cannot turn the brass without first expanding it?
In any case, I wouldn't worry about runout until the brass has been fired, especially if your'e dicking around with necking up/down. What you should see is a consistent neck thickness all the way around the neck. Within a tenth or two (you'll need a tube mic to measure this accurately).
Yeah I can't slip the new brass over the neck turning pilot. It creates very even neck tension! I just don't want to do it if it causes .004" runout.
What press are you using?
Are you lubing the expander mandrel, or inside the case neck before running them up to true the ID for turning?
What gauge are you using to measure this runout?
The whole idea of using the K&M Expandiron mandrel is so that the brass will have a true ID measurement to slide onto the pilot of the K&M turner. Once you have that true ID to index the pilot's turner on, the cutter should be trimming the OD of the necks true as well.
So, if there is more runout being introduced during the process of truing neck ID via mandrel, I'd speculate that its a result of stress during the press stroke.
Are you lubing the expander mandrel, or inside the case neck before running them up to true the ID for turning?
What gauge are you using to measure this runout?
The whole idea of using the K&M Expandiron mandrel is so that the brass will have a true ID measurement to slide onto the pilot of the K&M turner. Once you have that true ID to index the pilot's turner on, the cutter should be trimming the OD of the necks true as well.
So, if there is more runout being introduced during the process of truing neck ID via mandrel, I'd speculate that its a result of stress during the press stroke.
In my opinion you've got some unrealistic expectations. First off fireforming is part of the process and attempting to keep runout on a new case you are neck turning under .001" is pointless and uneccesary. I have turned thousands of cases and could care less if I get more runout after running them through the expander mandrel in preparation for neck turning. I actually expect to see it and don't care one bit because the next part of the process is fireforming the case. As long as you have a correct fit between the expander mandrel and the turning mandrel and the necks are a uniform thickness after turning I wouldn't worry about it. I feel it takes 2-3 firings to even get cases where I want them anyway so who cares how they come out getting them ready for neck turning. Let us know what the runout is after you fire them (I'll bet they'll be just fine).
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