general neck turning advice

R

Robbert

Guest
I am new to neck turning my cases.

I am now doing it with a Sinclaier neckturning NT-1000 tool.

My result is that I can feel (with my nail scratching along the neck) all very tiny marks as a result of turning.

Is this normal or should the result be 100 % smooth?

thanks for sharing your experience.

Robbert
 
neck turning

I am not an expert but have turned for a number of rifles I shoot. I have had some come out smooth and others with small lines as you describe using the same tool (differant brass). I have used steel wool to polish them, turning them with a drill and a Lee case holder. I doubt it makes alot of differance.
 
Robbert: I also have and use the Sinclair NT-1000 ( since 1998), but recently upgraded to the NT-4000/ excellent tool. Anyway, it's been my experience that the lines (look like screw threads ?), can be caused by pushing the case forward too fast. Try slowing down on your cutting feed. When it does happen, I just go over that area again, for an always smooth cut. In the process of prepping 80 new Lapua 220 Russian to 6ppc, for a pair of new chambers "as we speak", and am really impressed with the NT-4000: all the shortcomings of the NT-1000 have been fixed. Mandrels are interchangable so no additional expense there.
 
Thank you, but do the tiny markings left from turning invluence on accuracy in any form? shoot the case neck be really smooth and shiny again?:confused:
 
threaded necks

The small peaks and valleys on a turned neck may not cause a problem with accuracy. I think the high ridges wear down fast or are forced down,making
the neck thinner quickly. As it was previously mentioned, pushing the
case can cause this. It is also probable that the cutting edge is not
truely parallel to the mandrill. Adjusting the cutter to a very close position
to the mandrill and holding it up to a good light, it can be seen easily. If
the leading edge is high, the surface will look threaded , and if the trailing
edge is high, you will have tapered necks.
 
There are a couple of alert words (on this section we talk a lot about factory rifles--you know --the ones with the great big wide chambers-- and new to it begs a second Q as well) in the original post that prompt me to ask why are you turning your necks? The second is how are you measuring whether or not you need to turn a neck-- and how much you shave off?---ok it was 3 questions..........
 
Robert

Turning Necks is a machining proccess, and as with all machine work, the actual finish produced by the tool is predicated on the width, (or radius on most lathe tools), of the tip, or the feed rate.

As Bob said, the tool should have a rather wide cutting surface that is dead parallell to the mandrel. That helps alot in achieving a smooth cut, even if you do feed a little fast.

Since the neck is subjected to pressure, and a sizing bushing, it is understanable that the slight toolmarks will be "combed" down after a while, resulting in a neck that is just a tad thinner.

I would strive to get them as smooth as possible.......jackie
 
amamnn said:
There are a couple of alert words (on this section we talk a lot about factory rifles--you know --the ones with the great big wide chambers-- and new to it begs a second Q as well) in the original post that prompt me to ask why are you turning your necks? The second is how are you measuring whether or not you need to turn a neck-- and how much you shave off?---ok it was 3 questions..........
Click to expand...

thank you for your Questions!

answers: it is a factory rifle: Mauser M03 Varmint/match barrel.
the fired rounds come out with a neck wide: 8,76 mm (0.344 ") and a loaded round has dimension of 8.47 mm (0.333").
I measured the necks consistency (using a sinclair case neck sorting tool) and found that de brass necks had variences of 0.002"-0.003".
I thougth that could be better so I turned 40 cases (to 0.014" thickness exact) to compare against non turned necks.
I have shaved of 0.001" where necessary.
 
.308

sorry My caliber .308 using barnes 150 TSX bullets
 
Robbert

Turning necks can be fun, at least in the beginning. Given the
diameters you mention however, you may not see any improvement.
The .344 neck as fired was probably fired in a .345 neck or larger.
Some springback does occur even in new brass. Total expansion of
.012 leads very quickly to hard necks and when sizing that much
there is every likelyhood that concentricity suffers badly. You may
be able to make cases from say a 30-06 , thereby allowing a little
thicker neck. Annealing would no doub't be needed and the added
work may not show any increase in accuracy
 
Robbert, from sad experience i've learned that turning necks for oversized factory chambers might lead to slightly better accuracy, but it will certainly lead to much shorter case life. Unless you anneal your case necks ever few firings/sizings they'll harden and you'll get lengthwise neck splits.

If you sort your brass and only use cases with necks that are within 0.001" in variation you'll get the same accuracy improvement and longer case life. You don't mention what brass you're using, but it's likely that Lapua will be the best available and likely not too outrageously expensive in Holland (compared to other brass anyway).
 
Thanks a lot you all for your kind advices.

I think in my case I'd better not turn them and stick to seating depth, powder adjustments. and spend a lot of fun time sorting them out at the range.

regards
 
The problem is most likely that you are removing the turned case off the mandrel too quickly. There is spring in the cutting system so as you finnish the cut and screw it off it cuts somewhat on the way back.
This gets worse as the initial cut gets deeper and produces more spring.
Just take it slow and easy reversing the cut and it wil turn a fine cut on the way out. It is better to turn in two cuttings last cut to size being a fine cut.
When turning for a factory chamber the idea is to just turn the cases to a 75% clean up not a 100% cleanup. That way you preserve some brass thickness. Later on after a few firings you can clean them up a bit more with the same turner final setting.
Here we go again. Turning necks for a factory chamber requires a different approach to neck sizing , partial neck sizing and body dies is what is required.
This will allow part of the neck diameter to stay near chamber diameter permanantly and recover increased clearance caused by turning the neck down. This is for bolt action. If you would like a better explanation email me.
 
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Robbert

I cut necks using 2 settings one close and a finish cut. After the finish cut I run the case one more time not changing the setting. This gives a small skim cut and my cases come out with no ridges.

Stephen Perry
Angeles BR
 
robbert,
to your origional question. i havent used the sinclair tool, but they all basically do the same thing. slow down the feed is about all i can continue to add. what you are doing is basically, cutting a thread in and then one back out. run them back in, slowly and back out slowly, for a total of two passes.

whether you need to turn the necks or not is up to you, but for what you listed i would not turn them any thinner but to take the higher side off.
tom
 
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