Partial neck sizing

[michiman]

I have a couple hundred pieces of once fired lapua brass for my 6.5 cm. I was curious if anyone has had experience with the Redding competition neck sizing bushing die. It allows for partial neck sizing. I plan on body sizing all of the brass. I’m trying to decide if I want to size the entire neck or only a certain portion.

I plan on testing it at some point by sizing 25%, 50%, 75% and 100% of the necks and comparing. But wanted to see if anybody can share some experience.

Thanks

 

[Smallcalshooter]

Once you fire your brass in your rifle it should be about .001 smaller than your chamber. If you only size part of the neck the rest would remain larger helping center the round when you chamber it . After you find a good load you could try different amounts to see if it helps. Let us know how it goes. Good luck.

 

[Ryridesmotox]

It would be interesting to me to test all that. But I like testing weird shit with my gun. Seems to me that it would be more difficult to control neck tension with less than the whole neck being sized. But I honestly dont know. I didnt even know dies did that, but I can't say I've ever looked for one that did.

 

[michiman]

It would be interesting to me to test all that. But I like testing weird shit with my gun. Seems to me that it would be more difficult to control neck tension with less than the whole neck being sized. But I honestly dont know. I didnt even know dies did that, but I can't say I've ever looked for one that did.

I am gonna test it and will up date with results, probably wont happen until January.
as far as neck tension is concerned, i plan on sizing the necks, then using an expander mandril to get an inside diameter of .263 for the sized portion of the neck, this will leave the nonsized portion untouched. This will give me 0.001 of neck tension. It would be a bit tighter with just the neck sizing.

 

[ken4570tc in WY]

I partial resized necks for my .308 Win for 1000 yd competition. It worked well. Didn't need a special die. Slipped a skinny washer over the case to stop the die sizing process about 1/16" above the shoulder/neck junction. My best 10 shot group with the factory Savage was 7.6". I'm doing the same for my Gen 1 RPR .243 Win.

 

[LA260]

For my 308 1/3 sized necks resulted in a slower speeds by 25fps or so but better groups and lower ES and SD compared to 2/3 sized necks but not by much. For 260rem it made no difference and I haven't bothered to test with other calibers. I just size about 80-90% of the necks for all calibers now.

 

[glock63]

I size the neck down about 80% with good results.

 

[RegionRat]

With many bushing dies, the chamfer on the bushing doesn’t go all the way to the shoulder junction anyway. So, it tends to be a partial size unless you use a conventional die. It isn’t the percentage you are going to test, but it is still significant when compared to the conventional die at the shoulder junction.

If you single feed, there is nothing else to consider. However, in a repeater there can be issues when a partial neck sizing leaves a cartridge weak against bending loads. Make sure you consider the loads on the cartridge due to feeding.

Partial sizing due to the bushing chamfer also tends to mitigate doughnut issues due to the bushing leaving that junction expanded. That tends to be better for SD and ES issues.

 

[pabrousseau]

tag

 

[Milo 2.5]

a partial neck sizing leaves a cartridge weak against bending loads.

What are you saying here?

 

[michiman]

With many bushing dies, the chamfer on the bushing doesn’t go all the way to the shoulder junction anyway. So, it tends to be a partial size unless you use a conventional die. It isn’t the percentage you are going to test, but it is still significant when compared to the conventional die at the shoulder junction.

If you single feed, there is nothing else to consider. However, in a repeater there can be issues when a partial neck sizing leaves a cartridge weak against bending loads. Make sure you consider the loads on the cartridge due to feeding.

Partial sizing due to the bushing chamfer also tends to mitigate doughnut issues due to the bushing leaving that junction expanded. That tends to be better for SD and ES issues.

Why isn’t it the percentage that I’d be testing? Sorry may be I am misunderstanding you?

 

[Milo 2.5]

I have messed with partial neck sizings a good share. I started out trying it just to add some tension to necks already sized, with bushing dies. I have neck bushing dies that work for all cases I shoot, so was doing half to three quarter of neck for additional grip.
Now I load for 4 dashers, all prone to gassing the shoulders when fired, I honestly could not figure out why, so I do what you are wanting to do, just build a donut above the shoulder to seal it off. Yes, I know that is not your intended purpose, but that is what you will be doing.
You just need to know at some point, your brass will be hard to, or will not chamber, because every firing it adds some to the bulge. And at this time, constricting the bulge may push it all to the inside, so if you use the expander ball of the die, now your original neck tension is going to be skewed. I am not positive a mandrel will do that much better.
Be cognizant of what you are trying to do here, you may come out of it unscathed, or you may open a can of worms you are not prepared to deal with.

 

[918v]

What are you saying here?

I think he’s saying the cartridge isn’t sturdy enough for feeding from a magazine and will submit to bending forces resulting in runout on the bullet.

 

[Steel head]

Meh

I size as much of the neck as possible.
I don’t mess with that BR voodoo unless I have to.

 

[Milo 2.5]

I think he’s saying the cartridge isn’t sturdy enough for feeding from a magazine and will submit to bending forces resulting in runout on the bullet.

Ok, thanks. In every instance I have messed with it, my accuracy has improved, all my rifles are mag fed, so personally, I have to discount the theory

 

[RegionRat]

when expanding neck with turning mandrel after sizing in redding s bushing dies, do i have to neck turn?

Ok, thanks. In every instance I have messed with it, my accuracy has improved, all my rifles are mag fed, so personally, I have to discount the theory

If it works for you, then no worries. Sometimes the amount of jump is near zero or into jam and the bullet can tolerate the weaker moment stiffness.
Other times, if the load has a seating depth that is deeper, and the partial neck sizing leaves the moment stiffness weak, then the feed forces can move the bullet out of alignment and it may or may not help. It is hard to say when the contribution of a reduced grip cross the line of being too weak, but it tends to move the balance in that direction as the support length gets shortened.