Neck turning issue

F

feffer

Member
Making brass for a 30x44 from .308 Win with Norma cases. Process: cut most of the neck off the .308, run it through the form die, and fire-form with Unique (no bullet). Ready to turn the necks, but having a problem: the necks are expanded with the K&M mandrel, but do not fit on the pilot. I think it is because the newly formed necks are thick (.017+) having been formed from the .308 shoulder brass, and do not expand and "hold" like thinner case necks would. That's my guess, but in any case, they are way too tight for the pilot.

Here's what I've tried. 1) Inside neck ream first on my Forrester lathe-tool. This works, but now the neck is a bit sloppy on the K&M pilot. 2) Outside NT entirely with the Forrester tool. This works, and is how I've done cases in the past for this barrel. The turned necks are "pretty good" but not consistent to the ten-thousandth, like I can get with 6PPC cases using the K&M tool. 3) Tried other 30 cal expanders that I have, but same result as with the K&M one...still too tight case fit.

Should I try to hone the K&M pilot down until I get the proper neck fit? What's the best way to do this? Any other suggestions?
 
Stick with the K&M Pilot and Turner and the K&M Expander Mandrel. I ensure good fit by running the case neck up on the Expander a few times rotating the case about 120 degrees each time and then immediately going to the Turner with no elapsed time in between. I don't batch process when it comes to turning. Expand then turn. Have had no problems with that sequence. If you continue to have problems, call Roger. He'll get you squared away. :)
 
Same Problem Here

I'm working with a different case, but having the same problem. The only thing I have found that helps somewhat is to repeatedly expand the neck over and over. I don't have to turn off a lot, so I am using the K&M turner with flutes and carbide mandrel. I am using a neck turning machine. The carbide mandrel helps a lot and lube.

I tried a reamer, but when I use it not all of the neck is cut. Without the reamer all of the neck is cleaned up. Sorry I could not be give better advice.
 
Agree, but don't have one. Won't get one either just for this barrel. Going to have to somehow make do with what I have.
My K&M pilot mics .3085 and the K&M expand-iron mics .3070; so theoretically this combo should work. I'm pretty sure the problem is the extra thickness of the neck coming from what was case body brass on the original .308 cases. I even tried annealing after forming to try to soften up the new necks. The thicker necks just seem to spring back more and become too tight to fit the mandrel.

I'll try calling K&M to see if they have a suggestion, but I think the only options are honing down the pilot to fit, inside neck reaming or perhaps removing some neck thickness with my Forrester ONT tool whose pilot does fit. Will have to play with this a bit more.
 
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A couple of months back, when I was re-turning some brass for slightly more clearance, my turning mandrel was stopped at the neck shoulder junction of some of the cases by a doughnut (the only situation where I believe doughnuts matter with short bullets that are seated out of them). I was not in a big hurry, and there was a show on the TV that I was watching, so for those cases, I simply left the case on the expander for a minute, which allowed me to insert the turning mandrel and turn their necks. There was more resistance when inserting the turning mandrel, but not so much that I could not turn them. Obviously, if I had been in a hurry, or if there were a large number of cases, I might not have wanted to bother, but it was a batch of 15, for a PPC, and time was not an issue. Another thing, a slightly loose fit on a turning mandrel can still produce quite good results, if the proper technique is used. Back in the day, I was turning necks, having expanded them all first, and quit before I was finished with the whole batch. A couple of days later, I was surprised to find out that the necks that I have previously expanded were too tight to turn, requiring another trip through the expander, since then, I have done the whole process one case at a time, expanding, then turning.
 
feffer said:
Agree, but don't have one. Won't get one either just for this barrel. Going to have to somehow make do with what I have.

My K&M pilot mics .3085 and the K&M expand-iron mics .3070; so theoretically this combo should work. I'm pretty sure the problem is the extra thickness of the neck coming from what was case body brass on the original .308 cases. I even tried annealing after forming to try to soften up the new necks. The thicker necks just seem to spring back more and become too tight to fit the mandrel.

I'll try calling K&M to see if they have a suggestion, but I think the only options are honing down the pilot to fit, inside neck reaming or perhaps removing some neck thickness with my Forrester ONT tool whose pilot does fit. Will have to play with this a bit more.
Click to expand...

I may be a little slow this afternoon, but how do you figure an Expander Mandrel that expands a neck to .3070" is a good combo fit, theoretically or otherwise, for a Turner Pilot that measures .0015" Larger? It should be the other way around.

Glad you're calling Roger Miller at K&M but I believe he is on vacation till after the New Year.

You should Never Ever have to hone anything when parts are coming from the Same manufacturer. Let Roger take care of you.

His goal is to have his Expander expand a neck just enough so that the neck slides smoothly over his turner's Pilot, not too tight or too loose, without any need for jury rigging or intervention by a customer. Again, let Roger give you what you need. :)
 
@ abintx: of course you're right, I typed it wrong, the pilot is .3070
@ boyd: played around with it a bit more today. I think it is a doughnut (of sorts) because the pilot does get tighter near the neck-shoulder junction. At first I dismissed this possibility because these cases have been fire-formed with Unique and No bullet, but possibly running the case into the forming die created some sort of enlargement there. No amount of multiple expander hits is enough to get it unto that last bit of the pilot. The well-lubricated case binds every time.

I finally got one to work by jumping through a lot of hoops: ONT the formed case on my Forrester tool down to about .014, then expand again and run an inside neck reamer through to remove the doughnut, resize the neck, and re-expand it again (a few times) and finally it fit the K&M pilot so I could finish it there.

Really the better way is as abintx suggests...get a proper expander-pilot fit, so I'll just wait a bit and call K&M.

Incidentally, my reason for prepping new cases is because I'm concerned that my existing ones were cut too thin giving me about .004 to .005 total neck clearance, and I'm trying to get around .002 total. Maybe this won't even matter?
 
When I make 6PPC cases, if I do not turn into the shoulder enough, and have to force the bolt closed with a lot of effort, doing that makes a doughnut without firing a shot. Pushing the neck shoulder junction back forces thicker shoulder brass into the base of the neck. That is where doughnuts come from. It can happen slowly and gradually, over a number of firings, or all at once, as in my example. Did you try leaving the mandrel in the neck for a minute? That is different than multiple expansions.
 
Boyd Allen said:
Did you try leaving the mandrel in the neck for a minute? That is different than multiple expansions.
Click to expand...
Tried it after seeing your first post, and yes it does help. Not quite enough though to prevent the K&M pilot from binding.

Boyd Allen said:
Pushing the neck shoulder junction back forces thicker shoulder brass into the base of the neck. That is where doughnuts come from.
Click to expand...
Since my original brass is .308 Win, shortening and forming it moves a lot of thicker shoulder brass into the neck. In fact the entire neck except for the end 1/16th inch or so is from the .308 shoulder. I don't think I have a classic doughnut, but the thick brass "holds" it's dimension, so the result is sort of the same...way too tight pilot fit.

I tried annealing last night, to see if I could soften the neck a bit, but that did not do the trick either. To finish these 20 cases I started, I resorted to ONT on the Forster tool to go from .017 to about .013, now after your expand-and-hold trick, the cases WILL fit the K&M pilot. Years ago, I did some brass using only the Forster tool...2 passes. It was OK, but not as consistent as the K&M tool will do. I think long term, I either need to get an appropriate expander, or start with different brass.
 
One thing that I have done in the past, when working up 6PPC brass, expanding the .220 Russian to 6mm, was to make a rough cut using an old Sinclair turner, that has had its mandrel sanded down a bit, in combination with the K&M expander. This gives a really loose fit on the turning mandrel, but since I was taking a final cut of around .001, it did not matter. Also, technique will allow a looser fit than you might imagine. By holding turner loose, and not restricting the wobble of the cordless drill that drives the case, advancing to the shoulder much too quickly for a complete clean up, and then coming back to the mouth very slowly, the cutter has the neck pinned to the mandrel the whole way, and there is not force trying to lift it, like there is if you fight the wobble. With a little practice, you would be surprised at the quality that can be achieved with a relatively loose mandrel fit. I know that this is contrary to the majority of turning lore, but I have the proper tool to measure my results. All of the heating issues can be avoided with proper fit and technique.
 
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