Advanced neck sizing 101

[R.W.Dale]

I'd like to have a discussion about some of the more advanced or technical aspects of neck sizing rifle cartridges with accuracy being really the only concerns.

In my readings I've found that there seems to be four schools of thought with regards to the amount of neck sizing to do.

1. Neck size the entire neck just shy of pushing the shoulder back

2. Size only half the neck or whatever is necessary to ensure adequate neck tension

3. Partial length resize everything noting and measuring shoulder setback to be a minimum required for that rifle

4. Use a Lee collet die (where I usually fall, cept I don't own one for 308 yet)

Please share your findings and results that you've seen particularly if you've employed more than one of the methods outlined above

 

[jfdavis58]

I spent most of last summer pushing 308 bullets employing a variety of 'sizing' techniques during reloading. My ability to place accurate shots improved tremendously. Reams of paper, stacks of targets and lots of empty component containers.

In an over the counter rifle the most improvement occurs when the correct load/dimensions are found/discovered. Nothing else shows much statistical improvement.

In a 'tuned' rifle once again the right load shows the best improvement. Improving the dimensions of the case makes some difference (neck turning, trimming, uniforming primer pockets, chamfering)and these changes stick for several reload cycles.

The mixed bag of techniques you list provide a mixed bag of outcomes, none of which do much for just general purpose ammunition-hunting, target shooting some general competition). I suspect they do have specific application to extremely tight tolerance rifles and custom equipment and certain high precision activities, but....

In a 'custom' rifle-I don't know. They cost more than I'm willing to afford.

 

[ranger335v]

The Lee Collet sizes the full neck so that's not an issue.

There is no point in neck sizing below the base of bullet contact.

 

[243winxb]

The Lee Collet sizes the full neck so that's not an issue.

Partial neck sizing with collet die

If you want to resize just a part of the neck, find a washer at your local hardware store the has an inner diameter large enough to fit over the case, and an outer diameter large enough so that it contacts the collet sleeve that protrudes from the bottom of the die. Slide this washer over the case after the case has been inserted into the shell plate. Now when the ram is raised, you can still close the collet by applying force at the top of the stroke, but the case will not go up as far into the collet, and the neck will be sized less an amount equal to the thickness of the washer.

 

[Walkalong]

Partial neck sizing with collet die

If you want to resize just a part of the neck, find a washer at your local hardware store the has an inner diameter large enough to fit over the case, and an outer diameter large enough so that it contacts the collet sleeve that protrudes from the bottom of the die.

I cut a washer to fit the shell holder and epoxied it to the shell holder. .22 Hornet-years ago. I use a Redding bushing type sizer now.

 

[flashhole]

The 5th method would be to use the bushing type die. Some folks like the bushing type better than the Lee Collet Neck Die because they can adjust neck tension with the bushing. Neither of these methods requires pulling an expander ball up through the neck after it has been sized down. All the other methods you list require an expander ball that can distort the neck after it has been fire-formed then resized. Personally I like the Lee CND and have developed a feel for using it.

 

[MCMXI]

I neck size .308 Win cases with a Redding competition neck sizing die. I don't size the whole neck, more like 80% of the neck. I bump the shoulder back to SAAMI or SAAMI - 0.001" with a body die in a separate step and trim the cases to length. I was using a 0.338" neck sizing bushing since the O.D. of A-MAX bullets in the Lapua brass I have measures 0.339". Redding suggests 0.001" of neck tension. Here's the problem though. I found that the 0.338" bushing was giving me inconsistent neck tension due to the case neck wall thickness varying by 0.0015". My solution was to neck size with a 0.337" bushing, then run a R.W. Hart expansion plug (that I bought with a mandrel for neck turning) into the case neck. I then used the mandrel to check the internal neck dimension of each case. Talk about PERFECT. The mandrel fits so well that it rides on a cushion of air in the case. Anyway, when it came time to seat the bullets, every bullet went in with the same amount of resistance. The results at 300 yards were very encouraging and that was off a bipod during a match with a time limit and in windy conditions. I've posted that 17 shot group before but I put 15 shots for record into 2.555" at 300 yards. 14 of those 15 shots for record grouped in 1.693". I'm convinced that the load would shoot 1/4 MOA at 300 yards off a bench with a front and rear rest.

 

[flashhole]

1858 - post the target pic again. I always like to see how fellow shooters are doing. I wish we had a 300 yard range here in NY.

 

[243winxb]

Post 6 & 7 are close. Redding FL sizing Type-S Bushing die. If not neck turning, use expander on brass with large case neck wall thickness variations. Control shoulder bump. Size 1/2 of neck .002" smaller than a loaded round neck diameter. You want your reloads to be the same each and every loading. You can not do this with neck sizing only. Do your own testing, like i have , then you will know what works for you. Tiny groups require benchrest prep of brass. Post #10 below, good point. I find it takes 3 or more firings, sometimes, for the unsized neck to fully expand. After that, no more springback happens.This works best if the body is FLRSed. IMO. Why i do not like the Lee Collet die > http://forums.accuratereloading.com/eve/forums/a/tpc/f/2511043/m/6451001441 I must admit, never used one.

 

[flashhole]

I went back are reread the original post and thought bullet 2 deserves an additional comment.

When fired, the entire cartridge case will grow in size to fit the chamber, including the neck. Some guns, like my Ruger #1, are more generous in the neck region than others, like my Kimber Longmaster Classic that has a very tight chamber. The Kimber does not benefit by partial length neck sizing but the Ruger does. Not fully sizing the entire length of the neck allows the case neck to aid in centering the bullet to the bore. Of course the assumption here is the chamber is exactly concentric to the bore to begin with.

My point to bullet 2 is - partial neck sizing can have a larger effect on accuracy than just putting tension on a bullet because it can help with alignment too. The degree of improvement you will get depends largely on the guns chamber.

 

[flashhole]

Walkalong - I like the way you use that washer.

 

[jamesicus]

I use an RCBS neck sizing die (30/06) IAW the Manufacturer's instructions. I lube inside the case neck only using a .30 caliber nylon bore brush with Lee Resizing Lubricant. I do not clean the lubricant from inside the case neck.

James

 

[R.W.Dale]

On post 6 and 7

I may be incorrect but doesn't the use of a bushing type setup with no mandrel have a tendency to start to raise a dreaded "doughnut" at the neck shoulder juncture? I know folks like the Lee die because it pushes any neck thickness variations to the outside of the neck where it can then be turned off

I need to buy the stuff to neck turn for sure!

 

[243winxb]

a dreaded "doughnut"

A donut is formed when sizing to a different caliber, not a problem with factory brass. At least i have not run into it with 243win. Sizing down GI 308 to 243, yes, then i get a donut. Before outside neck turning, the inside of the neck is conditioned with an expander of some type. When using a Lyman neck turner, you just FLRS in a standard die with expander, then turn.

I need to buy the stuff to neck turn for sure!

The bushing die will get rid of "flyers" for the most part. Neck turning depends on how much you need to size. When the bushing has to size down a fired case more than about .008" , you run into problems. Then you need to size using 2 different bushing, in steps.

 

[flashhole]

I have not experienced a donut and it does not make sense to me that using a bushing die will bring a donut into being. I've been cautioned about donuts when re-forming brass where the parent case is larger than the re-form. The two re-forms that I do are 30-06 to 25-06 and 223 to 221 Fireball. In both cases the neck gets thicker but I only have to neck turn for the Fireball because my 25-06 has a generous neck. In the case of the Fireball I use an inside neck reamer at the same time I outside neck turn. Mine is the K&M system.

 

[JDGray]

Are we shooting factory barrels here, or benchrest customs? I have no problem obtaining .5moa groups with factory barrels, using Lee FLS dies. Someday I'll have a custom, and will have to employ all these advanced methods, but for now I'm pretty happy with the simplicity of FLS

 

[R.W.Dale]

Case forming aside I always undestood the doughnut phenomena as a brass flow issue from the shoulder into the base of the neck. A die without a mandrel doesn't iron this ring back out as one with a mandrel would.

I dunnow it's all theory to me at this point as I never have shot a lot of high intensity overbore cartridges. It did seem as though on the handloading specific boards the 243 guys were battling with the issue the most

Are we shooting factory barrels here, or benchrest customs?

Custom, 30" McGowan chambered for 308win screwed onto a savage right bolt left port target action. For me for this rig .5moa won't be but about 1/2 way to where I want to be.

 

[243winxb]

krochus, i am not sizing in the "donut" area of the neck as i only size 1/2 of the front part of the neck. I would guess this to be true >

the doughnut phenomena as a brass flow issue from the shoulder into the base of the neck. A die without a mandrel doesn't iron this ring back out as one with a mandrel would.

I have measured the thinning of the neck wall when using standard dies with an expander. This really depends on the die set, and the orginal neck wall thickness. It will not happen 100% of the time, if at all. The donut is only a problem if the bullets base come incontact with said donut. JDGray, i am shooting factory, Rem 40x & Rem 600, now. Had many other 243win before.

 

[MCMXI]

Case forming aside I always undestood the doughnut phenomena as a brass flow issue from the shoulder into the base of the neck. A die without a mandrel doesn't iron this ring back out as one with a mandrel would.

Here are some photos for demonstration purposes only. Normally, I would bump the shoulder back with a body die and trim the case to length, prime and add powder. The following photos show a fired and cleaned case, a neck-sized case using a 0.337" TiN bushing, the case after the R.W. Hart expansion plug has been run through the neck, and a seated A-MAX bullet. You can see a slight "donut" at the base of the case neck and you can also see that I neck size about 80% of the neck. This has given me the best results. The A-MAX bullet in question does extend down below the neck so I could run the neck-sizing die down to the bottom of the neck but the "donut" phenomena was worse when doing that and it left a noticeable ring even after the bullet was seated. If you look closely at the last photo, you'll see that the case neck is basically straight once the bullet is seated.

Case fired (three times) and cleaned:

Neck-sized with a 0.337" TiN bushing:

Neck expanded with a R.W. Hart expansion plug:

178gr A-MAX seated to touch the lands:

Outside of case neck is very, very close to being straight:

 

[MCMXI]

1858 - post the target pic again. I always like to see how fellow shooters are doing. I wish we had a 300 yard range here in NY.

Here is the target in question shot using ammunition assembled as described in post #7. The shot in the 10-ring on the far right of the 15-shot group took the group from 1.693" to 2.555" i.e. it added close to 1" to the group. I'd happily have another right next to it rather than the left most shot in the 9-ring since in this GAME, small groups don't mean anything if you don't hit what you're aiming at.

 

[918v]

I like option number four.

 

[Walkalong]

I may be incorrect but doesn't the use of a bushing type setup with no mandrel have a tendency to start to raise a dreaded "doughnut" at the neck shoulder juncture?

Donuts can be caused when turning necks, but not from neck sizing unturned brass with bushing dies.

That is not a "donut" in 1858's pics. That is just where the neck wasn't sized. (Partial neck sizing) Nice looking round though.

I loaded some Hornady 178 Gr A-max's for my sons FIL, but I just FL sized the cases. He could never benefit from any small gains in loading any other way.

He likes them though. The second load I tried got thumbs up from him, so all is good.

 

[flashhole]

OK, great pics but now I'm confused. Your donut was brought about via the process steps you used to process your brass and is exactly what I was describing in post #10. Partial neck sizing will allow the brass to fit snugly in the chamber. For whatever reason, I've always been under the impression the donut, at least the undesirable type, is on the interior of the case neck, not the exterior. An inside neck reamer will not affect what you have done with your brass at all but the inside neck reamer is what is prescribed to get rid of the donut.

 

[flashhole]

Walkalong - is your assertion a donut brought about by neck turning is the undesirable type because it is remnant brass from the turning process? I'm not challenging what you said, I'm just trying to be clear on the issue.

 

[Walkalong]

I am saying that is not a "donut". Donuts are a side effect of neck turning. They do not always show up. It depends on if the necks were turned down far enough into the shoulder.