Rimless Bottleneck Case Resizing Dies

[Bart B.]

Just curious.......

What do you think is the best resizing die for accuracy; neck only or full length?

[tangolima]

The only experiment I have done is Lee Enfield #1 mk 3 in .303 British. Not a rimless round per se but it is practically rimless. The rifle has a bit of headspace issue. I let the shoulder grow till it is headspaced on the shoulder, instead of the rim, so it is a de facto rimless round in that rifle.

I started with Lee collet die, and switched to full length resizing. There is no change to the 2moa group size. There may be difference in accuracy between these 2 methods for the business of winning match and breaking record. But for what I am doing, neck sizing is a waste of time.

I still haven't found a buyer for the collet die.

-TL

PS. I misspoke. Neck sizing doesn't waste time. It is actually slightly faster than full length. But it doesn't improve accuracy. After a few loads I will need to full length resize, or it won't chamber right. It is waste of money rather.

Sent from my SM-N960U using Tapatalk

[burrhead]

Full length with 0.001-0.002 shoulder bump.

[44 AMP]

What do you think is the best resizing die for accuracy; neck only or full length?

Full Length resizer is "best".

Not a matter of "accuracy" in general but a matter of versatility.

You can adjust a full length sizer to only neck size, if you wish. No matter how hard you wish, you cannot adjust a neck sizer to full length resize.

[Unclenick]

Might possibly be neither but rather a roll-sizing die. Precision on the target can be adversely affected by the case head being slightly out of square or the rim bent. Conventional hand loading presses don't do anything about that, except possibly the flat platform on a Co-ax press corrects it a little, since that bears against the case head all around. I can imagine making a roll sizer's plate profile to straighten rims and square the case up a bit. But that is just my imagination at work, as I don't have one of these hydraulic wonders to play with.

[Shadow9mm]

Full length

[Bart B.]

Originally Posted by 44 AMP

You can adjust a full length sizer to only neck size, if you wish.

I disagree.

Please explain how it is adjusted.

Originally Posted by 44 AMP

Not a matter of "accuracy" in general but a matter of versatility.

Full length has s been a matter of improved accuracy since the 1960's.

You first must understand how a bottleneck case that headspaces on its shoulder positions the bullet in the barrel when fired.

[jetinteriorguy]

Originally Posted by Bart B.

I disagree.

Please explain how it is adjusted.

Full length has s been a matter of improved accuracy since the 1960's.

You first must understand how a bottleneck case that headspaces on its shoulder positions the bullet in the barrel when fired.

Please explain, I’ve been waiting for this for a long time.

[Shadow9mm]

Originally Posted by jetinteriorguy

Please explain, I’ve been waiting for this for a long time.

here's a couple videos from eric cortina explaining his philosophy on things, which make sense to me.

"STOP NECK SIZING YOUR BRASS!!!!"
https://www.youtube.com/watch?v=lLG2kSrD40g

"How do the best shooters in the World resize their brass for maximum accuracy?" where he speaks with a number of record holders.
https://www.youtube.com/watch?v=vaqg4sJvg24

[lugerstew]

jetinteriorguy
I'm not positive, but to me, I feel I can neck size by adjusting my full length die to only push the case shoulder back to the exact same position as a fireformed brass from your particular rifle. To me that would be the same as neck sizing.

[Bart B.]

Originally Posted by jetinteriorguy

Please explain, I’ve been waiting for this for a long time.

It's the same as dropping one Dixie cup into another. The inside one is perfectly aligned and centered to the outside one.

[Bart B.]

Originally Posted by lugerstew

I'm not positive, but to me, I feel I can neck size by adjusting my full length die to only push the case shoulder back to the exact same position as a fireformed brass from your particular rifle. To me that would be the same as neck sizing.

That's going to size the case body down too. Use a mic to measure case body diameters before and after sizing.

Neck sizing only reduces neck diameter, other case dimensions don't change.

[Hammerhead]

In my 300blk bolt gun I’m neck sizing only mostly because I’m lazy.
Running sub 40k psi loads because I only have pistol primers, and the brass is not growing at all at those pressures.
I think the accuracy is slightly better with neck sizing.
Especially with light bullets with a longer jump to the rifling.

[Bart B.]

What best defines accuracy one can count on; smallest groups fired or largest?

[Shadow9mm]

Originally Posted by Bart B.

What best defines accuracy one can count on; smallest groups fired or largest?

I go with the average.

[44 AMP]

Originally Posted by 44 AMP View Post
You can adjust a full length sizer to only neck size, if you wish.

I disagree.

Please explain how it is adjusted.

By only screwing the die body into the press enough to resize only the neck.

Originally Posted by 44 AMP View Post
Not a matter of "accuracy" in general but a matter of versatility.

Full length has s been a matter of improved accuracy since the 1960's.

You first must understand how a bottleneck case that headspaces on its shoulder positions the bullet in the barrel when fired.

I believe you missed my point about the FL die, I meant that it is "better" than the neck size only dies because it gives you the option of neck sizing OR full length sizing.
And, I believe I do understand how a bottlenecked case chambers and positions the bullet in the barrel.

Originally Posted by lugerstew View Post
I'm not positive, but to me, I feel I can neck size by adjusting my full length die to only push the case shoulder back to the exact same position as a fireformed brass from your particular rifle. To me that would be the same as neck sizing.

I'm a little confused by this, how does the shoulder move forward beyond "fireformed" brass? Firing the round forms the case to the chamber, never noticed it growing after that, so how do you "push it back" to fireformed dimenstions?

[Nathan]

Full length made for the chamber.

[kilotanker22]

I am with Bart on this one.

A full-length die begins resizing the case body as soon as the case is inserted far enough to make contact. The full length die is designed to adjust all dimensions of the case. That means reducing them along their tapered body. The only way to ensure that the case body would not be sized at all would be for the internal dimensions of the die be such that not even the largest diameter part of the case body will make contact with the die. This would be a neck sizing die.

Since we have established that the full length die will make contact with the case body long before the shoulder would contact the die. We could deduce that as the diameter of the case is being squeezed along the taper, the shoulder will be pushed forward since that is the only direction the brass can flow. Since the shoulder will be pushed forward a little, you will not be able to finish sizing the neck, without pushing the shoulder back a little. Even if the cases have the same base to shoulder measurement before and after, two things will be true. First, the case has been fully, or at least partially, sized. Two, the shoulder definitely made contact with the interior surface of the die. Since the neck was not the only part of the case sized, it is not neck sizing. A full-length sizing die cannot be set to neck size only.

To answer the OP's question, I prefer full-length sizing dies. I feel that the best way to be consistent is to return the cases and components to the exact same dimensions as the last time, or as close as we can get to that. When neck sizing only, the case is never set back to the original dimension. Every time you fire that case the dimensions will change as the brass loses the ability to spring back. Eventually, you will have to work the brass further to get cartridges to fit the chamber. This is more evident in some cartridges than others.

Since learning how to properly set up a full-length sizer die, I have noticed far more consistency in my ammunition. Better velocity spreads, consistent and predictable changes in behavior when changing components, and the ease at which I am now able to developed good shooting loads for my guns. My favorite full-length dies I have used are the Forster benchrest dies. They are not stupid expensive and they work really well for concentricity.

[jetinteriorguy]

Originally Posted by Bart B.

It's the same as dropping one Dixie cup into another. The inside one is perfectly aligned and centered to the outside one.

Well put.

[lugerstew]

Thanks Bart B
For some reason I didn't realize that the Fl sizing die was doing that the length of the case, maybe I had this misconception, because a lot of times I can put a fired brass in a case gauge, and it fits. But you are exactly right, today I took a Lapua 223 fired brass and measured it in 3 places along the body and it was around .003 bigger in all those places than a Fl resized Lapua 223 brass.

44 Amp, I think sometimes I get confused or don't explain myself well enough, I really meant that I thought I could neck size by adjusting the Fl sizing die to not push the shoulder back more than a fireformed case that I store in my drawer for several bolt action rifles I have. I have though, measured my brass fired from these rifles and found them to be .001-.002 longer shoulder than my fireformed example. I'm not quite sure why they are longer, except I think someone on here said I didn't have a true fireformed brass example because of brass spring back. Hope this explains myself better.
Thanks

[Unclenick]

When you run a case into a FL sizing die, the taper in the body profile is generally narrower than the as-fired case, so at some point in the process of pushing the case neck into the neck portion of the die the sides will start to make contact and squeeze the brass narrower. This makes the head-to-shoulder distance longer before it starts setting the shoulder back again.

[Bart B.]

Unclenick,

I've yet to see a full length sizing die completely iron out the pressure ring.

Such dies would have to have inside diameters smaller there than new cases.

What am I not understanding?

[rodfac]

Full length, the last I've heard, Bart...can't supply where I heard it but it was attributed to the bench rest bunch...Best Regards, Rod

[rodfac]

Full length, the last I've heard, Bart...can't supply where I heard it but it was attributed to the bench rest bunch...But it's a moot point for me personally: at 75, I can't hold that hard to see the difference anymore....good luck to you young-bloods. Rod

[zeke]

Originally Posted by Bart B.

Just curious.......

What do you think is the best resizing die for accuracy; neck only or full length?

Given the wide variation in rifles, chambers, calibers, dies and an individual's purpose in reloading; can you explain how anyone could state which die is better? just curious