OzFclass

Hey everyone,
I recently prepped some brass and had some mixed results. They had been full length sized and then mandreled. During this process I noticed about half went through these two operations easily and the other half where harder (normal, what I expect when full length sizing). As the difference was signifigant I separated them into two groups. The brass started at 0.015" to 0.016", I found the harder to size cases achieved good results after being turned, ranging from 0.0110" to 0.0111" (improving the inconsistency from about 1 thou to about 0.1. The easier group turned down to 0.0110" to 0.0102, so the consistency was not really improved at all but all brass should fit the chamber with about a 4 thou clearance. There was no order to the way they where turned (a harder one, then softer, then two hard ect.). The one thing I did try was to size a few down tighter with a bushing and then remanderel them, this slightly improved results but still a little more than half a thou inconsistency.
Has anyone experienced this before? Anyone have a solution? I thought that putting them through a collet die before the mandrel might help?
Obviously this batch is done but for future batches I would appreciate any insights into the situation,
Thanks

Josh, is this new brass or previosuly fired brass, If fired how many firings and have they been annealed?

Even with new cases I prefer to neck turn AFTER they have had a couple of firings. Seems to take a couple of firings to get good case form and sharp shoulder junctions. I always anneal before neck turning. I feel that softening the neck should be a little easier on the cutter.

I use a K&M hand turner with a 200rpm cordless drill and a shell holder. I use the K&M expander and run the mandrel into each case 3 times, rotating the case a little each time. I hop on one leg 5 times, poke my togue out 8 times, turn around 3 times in a clockwise direction then anti clockwise twice......... dont know if any of the later stuff helps, but it's worth a try.

I haven't experienced any inconsistancies in thickness.

Hey Dennis,
It's new unfired brass, i would have to at least partially turn to safely chamber a round.

Would it be worth trying a minimum required cut to start and running over them again once the brass is formed and worked a little.

I know that I have erratic tightness issues when my turner warms up. It's a K & M & I did 2 things to avoid that:

(1) I fitted it with the heat sink Stuart Elliott now sources from K & M (It helps my arthritic hold too).
(2) I immerse the mandrel & cutter blade in water between cuts by judiciously part filling a Berger .308 bullet box (also available from Stuart) & resting the adjustment nut over the box's rim.

Maybe this relates to on your issue.

Josh I am having similar issues but am neck turning for a tight neck, .312 7mm from 30 cal brass necked down. Because the resulting necks are very thick and some spring back more than others some are looser on the mandrel than others. I have been turning them down in three steps and am now getting better consistency. I have been thinking that perhaps turning the necks down a bit before fls-ing might help.
Steve.

It's worth a try Dennis, I'll try it if I can't find anything else. It just surprised me that half where fine and I could tell before I turned them which ones would be.
John, I constantly monitored the temp and didn't let it get hot, turned at a slow rpm and allowed the turner to cool. I don't believe temp was a major factor, especially as I could tell how it was going to turn out depending on the group the case was selected from.
Steve, I'm not necking down but it could be the same issue.
Thanks guys for your thoughts

Josh,
Just a couple of questions, as I have neck turned about 600 Lapua cases , along with 200 Norma cases, for my 284 Win barrels, taking the necks down to 0.013". I really havent had the problem that you are describing.
Are you lubing the inside of the necks, and/or (also) lubing the turning mandrel.
Has your K & M turning mandrel got the donut cutter on it.
Do you carefully clean the swarf off your equipment after finishing each case.

I HAVE HAD an issue with mayber 5 or 6 random cases out of the 800 that I have turned, whereby I hadn't done a perfect job cleaning the brass "swarf" off the cutting blade and mandrel after the last case,..........and it is tighter as the mandrel enters the next case. In each of those 5 or 6 cases, they measured 0.012 or very close too it. Basically a full one thousandth of an inch extra has been taken off them.
This has only occurred using the K & M turner mandrel with the Donut Cutter head on it.
These handful of incidents (way under 1%) have basically been "one off's", with never more than 1 in 100 as I proceed, and definitely not any pattern to it. In every case, I can put it down to my sloppiness , and not the way you describe your experience where there seems to be a definite pattern.
Since changing to the PMA Neck Turning tool with the 35 degree shoulder angle, and which takes the Sinclair Turning Mandrel or the PMA carbide one, for the last 200 cases turned, the hasn't been an issue with the "odd tight one". That could easily be as a result of paying better attention to cleaning the tool after each case.
I use a cotton bud to apply a good coating of the Hornady case lube to the inside of each case neck. It's the orangey/brown one that smells like pure lanolin . BRT showed me how they use it when I did an advanced reloading course with Stuart about 3 and a half years ago when I discovered F Class, and I have just kept using it because it works well.
To cool my Neck Turner, I use a supply of deeply chilled "gel" cooler blocks. Chilled works better than frozen, because the tool is easy to keep in the center of the gel pad while I spin the last case in fine steel wool, then put the next case into the shell holder(which is in a cordless drill that sits solidly on its battery) I just need to use a new , deeply chilled one every 20 mins or so, which means 3 or 4 are required to ensure that my Cutter doesn't heat at all

Thanks tony, I have been using a 21st century turner lathe and I would have to say that I'm really impressed with it. It does not have the donut cutter. I do clean the turning mandrel and cutter every time and then reapply sizing lube to the turning mandrel and a thin film on the outside of the neck for the cutter.
I'm thinking the issue is in the way I'm prepping them for the lathe not the actuall neck turning opp.
I will do some more a play around with it, in the mean time I'll use rougher ones for shorter ranges.

I can imagine how frustrating it is.
Are your expander mandrel, and your neck turning mandrel both of the same make/manufacture ?
That's a critical issue that is easily overlooked.

Yeah Tony they are both 21st century. I'll do some more testing and see what I can find.

Josh these things can be a pain. The problems with brass are usually due to variance in hardening and each case does at least 12 annealings in its manufacture. It is annealed lots of times because of work hardening after each re-shaping. Its not surprising we are going to see new cases vary within batches. It could boil down to a Monday or a Friday lot.

Another key variable is the amount of zinc which gives the brass its malleability. Was the brass poured from the start, middle or end of the run from the crucible before its drawn and worked? We don't know, but we know the composition can vary a little due to its position in the crucible thereby changing hardness characteristics. Brass unlike the best barrel steel is not re-melted.

On balance we have to assume new brass is not all the same, and an odd batch can be crap.

Denis has made a good point in reference to annealing which could apply to new brass and it is something I do when forming a wildcat case although standard cases should not need it if the reject rate is low. You soon find those variable cases when seating projectiles and set them aside.

John and Tony make excellent detailed points which control the heat generated from frictional cutting operations which you use too. For others, when overheating, the brass swells and sometimes bogs on your tool and you simply cut more. The aim is to get a consistent cut at a consistent operating temperature with plenty of lubricant which flushes and cleans as well. An old trick with the brass and hand tools is to immerse them in hot water before working to pre-heat. The other trick is to allow .002" over with the expansion mandrel which takes into account a bit of spring back and irons minor irregularities if you don't anneal before you neck size with a tighter bushing, then iron again with another mandrel of bushing size before turning.

So I’m thinking the issue lies with the initial necking and use of the mandrel which is work hardening the brass which is exacerbated by variable case hardness and wall thickness in the first instance, assuming you use plenty of lube. If you applied manufacturing principles, you would anneal before any change in shape. This means before initial expansion and before the neck sizing but not after re-ironing with a mandrel of bushing size. Mind you, this is all relative to personal specifications. Because you are re-manufacturing, you are setting up the case for its future life these steps may well be prudent.

After final annealing I always use a mandrel to work harden the neck to get consistent form and hardness.