Neck turner cutting uneven on shoulder

[bsumoba]

I was working on a new lot of Lapua 6.5x284 brass. I lubed them up, expanded them with a 7mm mandrel, and then proceeded to turn them on a PMA tool with a 35 degree cutter. I have turned necks before on 6BR and 6.5x284 lapua brass necked up.

I am cutting the neck to ~ 0.014". With a mic, I am seeing virgin brass anywhere from 0.0135"-0.0155", at least on this particular lot.

The problem (may not be a problem and is more of an observation) I am seeing is that when I get down to the neck region, the cutter is cutting a little more of the shoulder on one side and is cutting more on the side where the neck is thinner (0.014 or less) and the cutter is barely touching it or not touching the neck at all. See picture below.

I then cleaned them up and proceeded to load a dummy bullet in there and I am getting about 0.001-0.0015" runout on a loaded round into the neck I just turned, so it is not bad at all.

I am wondering if you guys have seen this before. I do not think it is an issue, but it is interesting because this means that the shoulder area that is being cut more, is thicker.

To make sure my set up was not wrong, I took some older lot # lapua brass that has been fired a few times and is unturned, used a neck die to neck the whole neck down, then expanded it and turned the necks (cutting the donut out) and the shoulder came out much more even. I also took the new lot # brass and fireformed 1 piece, necked it down, expanded it and turned it and I still have an "uneven" cut on the shoulder. Could it just be that I have one side of the brass that is a little thicker at the shoulder and I should not worry about it?

You can see that the cut is shallow on the shoulder and at 12 o'clock, you can see on the neck that the cutter did not touch a portion of the neck.

This picture shows the same piece of brass where the cutter cleaned up the neck, but the shoulder cut is much further down the shoulder.

 

[JRS]

Has the brass been trimmed to the same OAL prior to turning?

 

[fredo]

Have you trimmed that batch of brass to a uniform OAL before you turned them?

If not, you're seeing the variation in case OAL with reference to how 'deep' the turner is cutting...

 

[P1ZombieKiller]

or it's also due to the neck having that .001" run out (not being straight when being made and/or when expanding).

 

[bsumoba]

Have you trimmed that batch of brass to a uniform OAL before you turned them?

If not, you're seeing the variation in case OAL with reference to how 'deep' the turner is cutting...

Honestly, I have not checked them, but I would understand if the cut was deeper or shallow, but in this case, the cut is shallow on one side and deep on another side.

I will check OAL when I get home and will also see if maybe the OAL is uneven on one side versus another, but that seems unusual for Lapua brass.

 

[JRS]

If you haven't trimmed the cases, they are most probably not square. Thus the difference in cutting depth at the neck, shoulder junction.

 

[bsumoba]

If you haven't trimmed the cases, they are most probably not square. Thus the difference in cutting depth at the neck, shoulder junction.

Yes, chances are it is this, but I will confirm tonight and get back to everyone.

 

[spclark]

Cartridge brass is seldom as uniform in thickness as we'd like to believe. Evidence is what you report seeing in measurements from un-turned neck thickness. Those differences would be evident were you able to measure shoulder and case wall thickness too, as some folks have done before by various means.

Trimming new necks will square them up but unless you use your neck turning mandrel's stop as a depth gauge it may not affect whether new brass shoulders cut evenly or not. I trim brass but don't bother with the stop-as-gauge, just letting the cutter cut ever so slightly into shoulders before each case is finished.

I get most consistent turner cuts at neck and into shoulder using once-fired brass rather than brand new. Turning new I see what you report while my results down-range (sling & irons to 1,000 yards) tell me not to worry.

 

[Dusty Stevens]

Once you fire em itll be pure cosmetic

 

[BoydAllen]

Your uneven cut is caused by your case necks being at a slight angle to the case body. Check your cases for concentricity at the ends of their necks, before and after expanding. I have run into this when expanding up .220 Russian brass to 6MM. If you find that this is the source of your "problem" I can make some suggestions as to how to improve the situation, but as Dusty wrote, it is primarily a cosmetic issue that disappears after firing.

 

[Dusty Stevens]

This is why your neck turner needs to float on all axis

 

[BoydAllen]

Agree with the need to float, but that will not solve his "problem". Been there. Done that.

 

[fredo]

Aside from providing an depth index for a turner like the PMA (and K&M) to bottom out against, it makes sense to trim to uniform OAL...

If you're taking the time & making the effort to turn necks to a trued diameter, and controlling tension via bushing(s), wouldn't you want to have that tension imparted on the bullet from a uniform surface area (IE, neck length)?

I do.

 

[Hondo]

Had the same problem, was wondering if neck ex pander was not lined up true and was bending the neck.
Tried another brand of neck ex pander solved the problem got nice even cut at shoulder junction.

 

[Dusty Stevens]

Once you fire em, trim em and re-turn em theyll be perfect. Nothing reliable to index off of until theyre fired

 

[BenPerfected]

A friend cut down a 6.5 neck turning pilot/mandrel so I could get a custom tight neck fit on my 6Dasher brass. In my case it the pilot was cut to .2425....I think! He also put a slight chamfer on the end of the pilot so you could to push it in the neck so assure a tight fit. If the pilot was slightly loose in the brass after resizing.....threw that piece of brass out. Maybe threw out 10 pcs out of 200+ or 3-4%. I also had just switched from the Forester turning lathe to the Hornady lathe and the difference in smoothness and consistency of the cut was significant. The Hornady lathe and the help from a more experienced shooter worked so well, I spent the next 10 hrs. removing .0002-.0004 from every piece of my brass. Some cuts were only on parts of the neck. After the final cut, I measured neck wall thickness in 3-4 places to assure a consist neck thickness. My brass is now the best it has ever been and the results really show with improved neck tension consistency. I now only have two loaded round seating sorts 5-10 PSI and 10-15 PSI. Shot the reworked ammo last Sunday and the consistency of my shooting was the best it has been. All it takes is 1-2 odd loads and you can lose a position in a shoot or that perfect group.
You pro's already know this, some of us are still learning 8)
Merry Christmas,
Ben

 

[Elwood]

I was working on a new lot of Lapua 6.5x284 brass. I lubed them up, expanded them with a 7mm mandrel, and then proceeded to turn them on a PMA tool with a 35 degree cutter. I have turned necks before on 6BR and 6.5x284 lapua brass necked up.

I am cutting the neck to ~ 0.014". With a mic, I am seeing virgin brass anywhere from 0.0135"-0.0155", at least on this particular lot.

The problem (may not be a problem and is more of an observation) I am seeing is that when I get down to the neck region, the cutter is cutting a little more of the shoulder on one side and is cutting more on the side where the neck is thinner (0.014 or less) and the cutter is barely touching it or not touching the neck at all. See picture below.

I then cleaned them up and proceeded to load a dummy bullet in there and I am getting about 0.001-0.0015" runout on a loaded round into the neck I just turned, so it is not bad at all.

I am wondering if you guys have seen this before. I do not think it is an issue, but it is interesting because this means that the shoulder area that is being cut more, is thicker.

To make sure my set up was not wrong, I took some older lot # lapua brass that has been fired a few times and is unturned, used a neck die to neck the whole neck down, then expanded it and turned the necks (cutting the donut out) and the shoulder came out much more even. I also took the new lot # brass and fireformed 1 piece, necked it down, expanded it and turned it and I still have an "uneven" cut on the shoulder. Could it just be that I have one side of the brass that is a little thicker at the shoulder and I should not worry about it?

You can see that the cut is shallow on the shoulder and at 12 o'clock, you can see on the neck that the cutter did not touch a portion of the neck.

This picture shows the same piece of brass where the cutter cleaned up the neck, but the shoulder cut is much further down the shoulder.

I have experienced exactly the same with a batch of 6.5x284 Lapua brass. Have you measured the neck thickness after you have turned? because quite a few of my cases that I turn to 12.5 thickness are still woefully out, and in order to weed out the bad cases you need to measure them in four points. Quite often I have measured a case that read 12.5 on the first measurement only for it to read 13 when I turn the case one quarter. As I'm using a Mitouyo thickness gauge I'm quite happy that the measurements are correct.

I'm using the 21st century turner and I can now immediately tell if a case is going to be okay or not. The 21st century free floats and if the cutting head wobbles as I feed the case onto the mandrel I know I won't get a consistent cut.

I have just turned 200 cases from another 6.5x284 batch and haven't had to cull any cases.

 

[nmkid]

I was working on a new lot of Lapua 6.5x284 brass. I lubed them up, expanded them with a 7mm mandrel, and then proceeded to turn them on a PMA tool with a 35 degree cutter. I have turned necks before on 6BR and 6.5x284 lapua brass necked up.

I am cutting the neck to ~ 0.014". With a mic, I am seeing virgin brass anywhere from 0.0135"-0.0155", at least on this particular lot.

The problem (may not be a problem and is more of an observation) I am seeing is that when I get down to the neck region, the cutter is cutting a little more of the shoulder on one side and is cutting more on the side where the neck is thinner (0.014 or less) and the cutter is barely touching it or not touching the neck at all. See picture below.

I then cleaned them up and proceeded to load a dummy bullet in there and I am getting about 0.001-0.0015" runout on a loaded round into the neck I just turned, so it is not bad at all.

I am wondering if you guys have seen this before. I do not think it is an issue, but it is interesting because this means that the shoulder area that is being cut more, is thicker.

To make sure my set up was not wrong, I took some older lot # lapua brass that has been fired a few times and is unturned, used a neck die to neck the whole neck down, then expanded it and turned the necks (cutting the donut out) and the shoulder came out much more even. I also took the new lot # brass and fireformed 1 piece, necked it down, expanded it and turned it and I still have an "uneven" cut on the shoulder. Could it just be that I have one side of the brass that is a little thicker at the shoulder and I should not worry about it?

You can see that the cut is shallow on the shoulder and at 12 o'clock, you can see on the neck that the cutter did not touch a portion of the neck.

This picture shows the same piece of brass where the cutter cleaned up the neck, but the shoulder cut is much further down the shoulder.

I have experienced exactly the same with a batch of 6.5x284 Lapua brass. Have you measured the neck thickness after you have trimmed? because quite a few of my cases that I trim to 12.5 thickness are still woefully out, and in order to weed out the bad cases you need to measure them in four points. Quite often I have measured a case that read 12.5 on the first measurement only for it to read 13 when I turn the case one quarter. As I'm using a Mitouyo thickness gauge I'm quite happy that the measurements are correct.

I'm using the 21st century turner and I can now immediately tell if a case is going to be okay or not. The 21st century free floats and if the cutting head wobbles as I feed the case onto the mandrel I know I won't get a consistent cut.

I have just turned 200 cases from another 6.5x284 batch and haven't had to cull any cases.

My 6.5 brass looked/looks exactly like the 2 pieces in the picture. I cut down to .016 and the neck cleaned up partially. In 2 steps I ended up at .015 with the shoulder cleaned up as your picture shows. Also, my run out on 2 dummy rounds was the same as yours. Weird!! It's been a long road doing 200 Lapua cases but, it's done and I'm happy.

 

[BoydAllen]

Here is a little tip on turning technique that has given me good results over the years. Let the turner and case float. Do not fight the wobble. When you are making your cut, advance to the shoulder too quickly to make a clean cut. Leave as much material as you can to be cleaned up on the way back to the case mouth. When you get to the shoulder pause and then proceed back toward the case mouth slowly enough so that the cut looks finished, but quickly enough that you continue to cut all the way. After you get to the case mouth, stop, and do not go back. The point is to keep the neck pinned to the mandrel the entire time that the cutter in over the neck, and not to have anything trying to pull the neck off of the mandrel under the cutter. At this point you can use a trimmer that indexes off of the shoulder to trim to length, then chamfer and deburr. After that, wrap a wad of 0000 steel wool around the neck, pressing it against the neck, and spin the case under power for a second or so, then shove the wad of steel wool against the mouth of the case and spin it again to polish up the chamfer. For my most serious work, I use the tip of a knife blade to scrape off the small ridge that can be formed at the base of the chamfer. This is easy to do for a small set of cases that is typical of short range benchrest. This is something that I came up with on my own. you will not find any written reference on it that I am aware of. I choke up on the blade so that only the tip is beyond my fingers, hold it so that the edge is almost parallel with the inside of the neck, hold the case in my hand and turn it against the edge until feel tells me that the burr is gone. This is the same thing that the long angle K&M tool is designed to deal with.

 

[bsumoba]

So I measured my brass and all the tips were relatively straight and more or less, the same OAL. The fact that there might be a difference in OAL of the brass should not be causing the cut to be further down the shoulder on one side of the brass versus the other, especially if the mandrel and ID of the brass neck is tight and has very little play in it.

Yes, I let both my hands (one holding the turning tool and the other holding the drill) float, meaning if it wants to wobble a bit, I let it do so and do not force it to stay straight.

I am really thinking that the brass thickness at the shoulder is slightly thicker on one side versus another, especially given the fact that I am seeing anywhere from 0.0135-0.0155" in varying thickness at the neck. I cannot imagine this variation in thickness is only on the neck. Hence, when I get down to the shoulder, it will cut more material on the side that is thicker.

Is my train of thought flawed?