Beginner’s question re: bullet seating and neck lube

[sbhooper]

In 40 years I have never used lube on the inside of the neck. I put a bunch of brass in a quart zip lock, spray in a healthy blast of One Shot, shake rattle and roll, allow the carrier to evaporate and run it through the die. Never an issue.

Maybe if you split hairs for target shooting or something, it could help, but to me is no more than just another irrelevant step.

 

[skeeljc]

Here is an interesting observation. When I size .223 cases in a Wilson bushing neck size die the dimension from the datum on the shoulder to the base changes (decreases). The Wilson die sizes the entire length of the neck. I assume the bushing comes close enough to the start of the shoulder to change the shoulder angle slightly. Has anyone else observed this?

 

[RegionRat]

Yes, I have seen necks affect shoulders, (and I would be even more surprised when they don't).

In engineering analysis terms, we define the boundaries of parts in terms of how they are connected to the parts next to them. For example, a finite element model uses particular elements for solid connections versus ones that represent pins, slides, or other degrees of freedom.

If you can imagine that the parts of the neck near the mouth are different than the parts of the neck that blend into the shoulder, then you get what I mean. The neck is not a thin wall cylinder hanging in space vacuum, it has a continuous solid connection to the shoulder.

Then it stands to reason that the stiffness of the neck walls near the shoulder are not equal to the ones near the mouth. The neck is stiffer near the shoulder since it can't move unless it takes that radius blend with it, both in terms of elastic strain or permanent yield change.

When we move the shoulder, we affect the neck, and when we move the neck, we affect the shoulder. There is a long discussion of how much, but the easy version is that the bigger those moves, the more likely you will also move the other connected parts. It may or may not be significant to our brass function, but it is up to us to manage it. Normal reloading is one thing, fireforming or wildcating is another...

Lubrication can be a tool to use when cold working metal. The forces on the brass are vastly different with and without lube, so it is easy to see how bullet grip can be affected by lubrication as well.

 

[skeeljc]

My Redding Type S FL bushing die only sizes 75% of the neck and it does not affect the shoulder at all.

Do you get better alignment of the cartridge in the chamber with some portion of the neck left unchanged from the previous firing?

 

[Old Tanker]

I only use neck lube when sizing with a full length sizing die with expander ball. It allows the mandrel and ball to be removed smoothly without pulling on the case shoulder where it joins the neck. This keeps my shoulder bump consistent. Never thought to use it for seating. I guess what’s left in the neck, after sizing, may help. Don’t use inside neck lube when sizing with a bushing.