bullet/neck tension - Does this idea make sense?

[Bayou]

Been thinking lately about crossing over to the dark side and turning necks like the BR guys do. The way I understand it you turn case necks to get consistent wall thickness so there will be uniform tension around the bullet perimeter and reproducible tension from load to load. The problem being that if you have neck wall thickness variations and you neck size with a bushing the places with thicker walls exert higher tensions on the bullet.

OK that's easy enough to understand and it makes sense to me, so here's the idea I was thinking about. Instead of doing your final neck sizing step by squeezing from the outside in with a bushing die, what if you do it by pushing from the inside out with a Lyman M die? Would it be true in this case that neck wall thickness variations would not cause bullet/neck tension variations because you would always be sizing to the same case mouth inside diameter? I measured the diameter of the bullets I'm using and the diameter of the sizing plug on the Lyman M die and the sizing plug is 1.3 thousandths of an inch smaller which seems like a good difference for proper tension. So I was thinking first I would neck size with a bushing that's a few thousandths too small, then open up the neck a bit with the Lyman M die and I would get consistent neck tension without the need for neck turning. Does this make sense or am I missing something here? Thanks for any feedback.

 

[QuiggyB]

Re: bullet/neck tension - Does this idea make sense?

When you use any neck die, the last thing through it is an expander ball moving from the inside out.

With turning the necks one part is getting even tension all around the bullet. Another is making each round identical to the other. I personally do it for my target shooting rounds but I don't think it is the most important thing I do in the whole process. It is a one time operation though compared to trying to rig up an extra step each time you load a round to get around it.

 

[Bayou]

Re: bullet/neck tension - Does this idea make sense?

I traced down excessive run out to the expander balls in my Redding bushing neck sizing dies so I removed the expander balls and don't use them anymore. Usually I don't do any expansion step. Firing the case expands the mouth, then I normally just squeeze it down with a bushing die leaving out any expansion step.

Doesn't material flow into the neck area from shooting so that neck turning is usually done periodically during reloading and not just once?

 

[Jeffvn]

Re: bullet/neck tension - Does this idea make sense?

I stopped using expander balls a long time ago. because of the run out they induced. I use a full-length bushing die (Redding Type "S", Redding Competition, Warner Custom, or Neil Jones Custom) to bump the shoulder (from 1/2 thou to 1 thou) and size the neck every time I load brass.

Multiple neck turnings - until recently I would have said no need. However, I realized that for my F-Class 7WSM enough brass flows with that cartridge (hence the need to periodically trim the necks) that during the life of the brass (I get somewhere between 10-15 firings per case before they go into the recycle bin) I will need to do a second turning on the brass to take it back to the 0.013 that they started at. There is a thread in the reloading section somewhere about this, where several of us discuss the topic.

Jeffvn

 

[QuiggyB]

Re: bullet/neck tension - Does this idea make sense?

Would you think the self centering expander balls like the carbide ones redding sells (they float side to side on the decapping rod) would still cause an issue with runout? I suppose since I am turning necks and using bushing dies I could do away with the ball entirely.

 

[MALLARD]

Re: bullet/neck tension - Does this idea make sense?

you really shouldn't be neck turning unless your using a tight neck chamber. any gains of uniformity or offset by the increased case neck expansion of turned down cases.


to the op, are you running a tight neck chamber ?


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bayou</div><div class="ubbcode-body"> So I was thinking first I would neck size with a bushing that's a few thousandths too small, then open up the neck a bit with the Lyman M die and I would get consistent neck tension without the need for neck turning. Does this make sense or am I missing something here? Thanks for any feedback. </div></div>

ha , that sounds like some crazy thinking. How much tension are you using ? I doubt you'll see an improvement in accuracy. I would just stick with neck sizing without the expander , put some lube on necks and run them slowly and you should get good accuracy.

but hey , if your expanding idea works you should make a post and include some pics.

 

[TexIndian]

Re: bullet/neck tension - Does this idea make sense?

The Sinclair Expansion mandrels are a much better tool for expanding necks and giving you a perfectly round and centered I.D. That M die was designed to open up the neck a tad when seating lead bullets so you won't shave away any lead. It wasn't made for this purpose. But I admit I've never used one for this purpose, so who knows?

And to answer your question, neither type of expansion tool will address the neck wall irregularity issues you mentioned. They will push the irregularities to the outside so that your bullet is more concentric with the case, but they won't address variations in neck wall tension.

 

[PeterN]

Re: bullet/neck tension - Does this idea make sense?

I have Hart/Nesika .272 no turn neck 6BR and I have used the better part of an 8pd jug of Varget experimenting with neck tensions. Nothing seemed to make a difference