Neck turning problem. Need advise

[DngBat7]

Pictured below is the issue I’m having. Brand new unsized Lapua from the box, I necked up to .30 from 6.5. Used 2 separate mandrels from 21 century. Then used the expander mandrel for the 21 century turner setup. So essentially got mandreled 3 times which I know caused a lot of turbulence. So I understand why the problem is happening, but what do I do to avoid it? Am I suppose to run an expander ball or something to straighten the neck and shoulder out before turning?

There is already a bunch I have done this way, and does not seem to affect accuracy, The gun has been very accurate. But if this not right, I want to fix it.

 

[Ccrider]

Don’t cut so far down into the neck. Turn close to your desired thickness to be safe to shoot, fire once (or twice) and then do your final turn.

 

[AckleymanII]

I make my first turn at 6.5. Part of what I turn goes into the shoulder when I neck it down, leave a tad bit to clean up at 30 cal. You are done!

 

[457ciSBC]

Obviously, the case neck to center line of the body needs to be straight, but the mandrel setup that you are using to spin the case needs to fairly straight as well. What your setup for securing and turning the case? Also, are you lubing the inside the case necks at each expansion step?

 

[boltfluter]

When necking up this far you might consider fire forming with no bullet. Or full length sizing pushing the shoulder back .005 or so. Be sure and put the bullet hard into the lands for first firing if using the die method.

Paul

 

[243Lapua]

Pictured below is the issue I’m having. Brand new unsized Lapua from the box, I necked up to .30 from 6.5. Used 2 separate mandrels from 21 century. Then used the expander mandrel for the 21 century turner setup. So essentially got mandreled 3 times which I know caused a lot of turbulence. So I understand why the problem is happening, but what do I do to avoid it? Am I suppose to run an expander ball or something to straighten the neck and shoulder out before turning?

There is already a bunch I have done this way, and does not seem to affect accuracy, The gun has been very accurate. But if this not right, I want to fix it.

Don t worry that's normal. Fire away.

 

[mikecr]

Turn at 26cal, trial & error, until desired 30cal thickness is attained after expansion.
I might even have a formula around here to get you close (as predicted).

 

[rwj]

It would appear that expanding the neck also moved shoulder material. Perhaps consider using a body die to restore the shoulder shape/contour before neck turning?

 

[DngBat7]

Thanks everyone. All great advise.

 

[Martin52]

Looks like you have matched your cutter blade angle to the shoulder angle however the neck may be slightly offset as a result of the expander setting.

 

[1911nut]

“Brand new unsized Lapua from the box,…”

I wonder if full length sizing before the last mandrel step would straighten the case?

 

[Shooter13]

Call John at 21st Century, I had this same problem and he said it didn't hurt anything but they were coming with a fix, I never checked on what it was as it didn't affect accuracy, also please post here what he said or we need, it isn't your blade angle or anything else.

 

[DJSBRS]

When expanding or reducing neck diameter, to keep this issue above to a minimum, you should do it in many small steps and lubricate between steps to refrain from stressing the shoulder angle area (collapsing or stretching shoulder angle). However, in this picture above, the turned cut appears to be correct. The slight shaved cut on the high side of the shoulder is insignificant.

You could have full length resized it prior to your final tuning mandrel expansion to align the neck to the shoulder and push the shoulder back to square it up. Most shoulders are not exactly square new from the box anyway. Expanding or necking up or sizing down down on 35º and 40º shoulders are more apt to collapse slightly even lubricating after every expansion or reduction.

Just my .02¢ worth.

DJ
DJ's Brass Service