Neck Sizing and How Much

[fe1]

How does one determine how far down the neck to size?

 

[BoydAllen]

Far enough so that any pressure ring falls well within the sized area...

 

[fe1]

Far enough so that any pressure ring falls well within the sized area...

How is the pressure ring identified? This is for a 300RUM with 210 VLD-H bullets.

 

[jonbearman]

Mic the bullet at the bearing surface and mark the highest reading and make sure you size it alittle past that point so you don't run into the area not sized.

 

[BoydAllen]

With an accurate (.0001) micrometer...... Not all bullets have them. If yours does, it will be an enlargement of diameter, over a short area, where the BT meets the body of the bullet, or if you were working with a FB bullet, at the base of the bullet.

 

[fe1]

So if there is no pressure ring on the bullet does the whole neck need sizing?

 

[BoydAllen]

It may not anyway, but yes, you could say that. The issue is that when the pressure ring passes through the sized part of the neck, and goes on past it, the neck tension is reduced. On the other hand, when the bullet is seated so that the pressure ring is within the sized part, it helps make the bullet more secure in the neck. Have you measured your bullets with a suitable tool? The Sierra BTs that I have measured do not have pressure rings. Others that I measured do. In those cases where I have seated bullets so that their pressure rings were below the sized area, I could feel the pressure pop out, on the back side, and the force required to seat was noticeably reduced from that point on.

 

[mikecr]

How does one determine how far down the neck to size?

There is no formula. Best to begin is far enough that springback grips the bullet sufficiently. Around ~.200" to as little as .125". It don't take much really.
Leave yourself some adjustment room, as you can fine tune with it later.

There is nothing good in sizing the entire neck length(including donut area). This only serves to add tension variance.

 

[jlow]

How does one determine how far down the neck to size?

There is no formula. Best to begin is far enough that springback grips the bullet sufficiently. Around ~.200" to as little as .125". It don't take m

uch really.
Leave yourself some adjustment room, as you can fine tune with it later.

There is nothing good in sizing the entire neck length(including donut area). This only serves to add tension variance.

If one does not size the whole neck, presumably with a bushing, how much does case length variance affect neck tension consistency?

 

[mikecr]

You're talking about a pile of variables there.
You've got whatever reason your cases vary in length, and what that's doing to hardness/thickness. Then you've got area/cal of your necks, brass composition, seating DTL, etc. And each with their own variances.
So nobody could tell you how much more or less bullet grip changes(even in their own cases) without isolating it, and there are no tools on the market to do this.
That's why I say there isn't a formula, or even a credible rule of thumb, for neck sizing length.
Too many variables in a pile..

As far as tuning, this is another pile. It all comes down to an actual plan, with understanding and consideration of plus/minuses to combinations.
Or pure luck..

 

[BoydAllen]

That is why I like to do all of my tuning at the range. Things that would take multiple trips to the range, loading at home, can be resolved rather quickly. It is a lot more efficient with regard to time and cost. Good old cut and try....with a bit of planning thrown in, or not...depending.

 

[jlow]

It was more of a theoretical question. Necks can be close to 1/2" in length and so that's in the multiple thousands. So even differences in 10 thousands is less than 1%. So it would seem hard for any tool or person to notice a feel difference in seating and notice a difference we frequently do. MV wise perhaps.

 

[artbosco]

How does one determine how far down the neck to size?

Some dies, like Harrell's, have a cavity for bushings that float. When the neck is sized their F/L Bushing die automatically sizes approximately 70% of the case neck. There is no determination needed with this type die, since the die was designed to size a predetermined length. With other bushing dies you can usually adjust the stem so that the bushing moves as much as you want it to, within limits. A slight audible rattle tells you that the adjustment made will usually give you the 70% most prefer.

 

[mikecr]

All else consistent and equal, I seriously doubt 10thou more or less neck length, contributing to bearing grip, could be measured as significant -unless sizing is taken into donut. Things are amplified there, so nobody should be sizing or seating near donuts.

As Outdoorsman says, bushings generally keep us from donuts(sizing-wise).

 

[jlow]

Thanks! That was my thinking too but wanted to hear what others thought.

 

[fe1]

How does one determine how far down the neck to size?

Some dies, like Harrell's, have a cavity for bushings that float. When the neck is sized their F/L Bushing die automatically sizes approximately 70% of the case neck. There is no determination needed with this type die, since the die was designed to size a predetermined length. With other bushing dies you can usually adjust the stem so that the bushing moves as much as you want it to, within limits. A slight audible rattle tells you that the adjustment made will usually give you the 70% most prefer.

My die is a Redding Competition Neck Bushing Die so therefore I am able to size as much or little as needed. I think you answered my question with the 70%.Otherwise it will be load and see how it shoots. I thought there might be a rule of thumb as a guideline.