Novice Questions on Resizing Die

[Phil3]

I am sure most of what I am puzzled about is elementary to most here, but hopefully that will make it easy to explain.

My understanding is that a conventional resizing die will resize the case and the neck, centering the neck so that the outside is concentric with the case. I also read that Redding Type S dies use neck inserts to resize the neck to a desired diameter, and that these inserts float to center themselves around the neck. If the neck is not centered with the case, how can that be good? What am I missing here? If there is no floating neck insert in a Forster die, and Forster will hone to your neck diameter, that would appear to be the way to go, assuming the neck portion of Forster die is concentric to the case. Don't hit me too hard on the naive question, just a novice trying to make sense of it all.

- Phil

 

[NorCalMikie]

I'am guessing that "all" dies are bored down the "center line" of the die so it would be pretty hard for the neck portion to be off center to one side of the bore? The body of the die that the case fits in is in line with the neck. If one side of the neck wall is thicker then the other side, neck turning would be in order.
Someone correct me if I'am wrong. (been wrong before) ;D

 

[watercam]

The neck bushings are held to center by the walls of the die. They do not float side-to-side to any appreciable amount. The set up is to tighten the retaining nut until it touches the top of the bushing and then back off 1/16 turn or so. Frankly I have screwed up and sized cases with the nut tight onto the bushing with no ill effect. For what it's worth Forster now offers neck bushing dies as well. One normally removes the button from the stem and chooses a bushing that will give about .003" neck tension with rounds that will be cycled through a magazine or .001-.002" for rounds that are single loaded (a la Long Range competition). In the end the brass lasts longer and with repeatable neck tension is more accurate.

All that being said, I've loaded some really accurate rounds with plain jane conventional dies. Technique trumps technology.

 

[Phil3]

The neck bushings are held to center by the walls of the die. They do not float side-to-side to any appreciable amount.

Redding says this about their bushing dies.

"...Concentricity is enhanced by the ability of the bushing to self-center on the neck of the cartridge case...".

To me, that means the bushing does move to side to side, by design. If the outside of the neck is not centered with the centerline of the case, then the Redding die does nothing to correct this to my way of thinking. Someone set me straight if I am wrong.

- Phil

 

[Phil3]

That helps a lot, thanks. So, good to start with used brass, for the purposes of having the outside neck and case made concentric through the pressure of firing. Makes sense. That means the inside neck could be misaligned, due to neck thickness variations. This is where neck turning comes in I presume. Neck turn a new case, fire it, and now the outside will be concentric (as stated earlier), but now the inside will be as well, because of consistent neck wall thickness. I hope this is right.

I understand how the bushings permit exact neck diameter sizing. But, I have also heard they may not neck size all the way down. Why is that, and would that not lead to the formation of a ring (is this the donut?) near the shoulder junction? Not sure why this would be bad.

It appears then that using a bushing for a bigger neck (tighter fit in the chamber) will also at the same time decrease tension on the bullet. A bushing that results in a smaller neck diameter will increase tension. It does not appear one can independently affect tension or neck fitment in the chamber without affecting the other. Correct?

I will be using dies for an AR15 in .223, but also will use the same dies for an accurate bolt action. I recognize the AR needs to have a somewhat looser fit to ensure reliable chambering.

Thanks.

- Phil

 

[Phil3]

No bullet runout would indicate the case, neck, and bullet are all concentric, but as you said, only if brass is high quality. If the neck thickness varies, either the outside neck is concentric and the bullet isn't, or the inside neck (and bullet) is concentric, and the outside case neck isn't. Seems to me that measuring the neck and bullet runout would best assure everything is in order.

From a cutaway of the Redding die, it looks like the bushing sits against a shoulder, thereby limiting how much neck is going to be sized. Is the height of the bushing adjustable? I don't have one of these dies to handle, and can not find instructions anywhere to learn from. Your comments indicate bushing height is adjustable, I just don't see how by looking at pictures.

I see that Redding recommends selecting a bushing size that is slightly under the outside neck diameter of a loaded round. How can that work, if varying brass has different neck thickness? Or does the use of bushing have the prerequisite of using brass that is consistent in neck thickness?

Thank you.

- Phil

 

[Elkbane]

Phil,
You have your thinking reversed about the doughnut. A doughnut sometimes forms on the inside of a case at the neck shoulder junction, usually from forming brass from a different caliber where thicker brass from the shoulder flows into the botton of the neck. WHen you run it into a die, the neck compresses to a fixed consistent OD (along the length of the neck) but the expander button doesn't drive the extra brass thickness to the outside during extraction. You end up with a slight constriction at the neck/shoulder junction.

The Redding bushing type dies do not, as you correctly surmised, size the whole neck down to a crisp shoulder junction. But this is nothing to worry about - unless you are turning the necks. The "swollen" portion of the neck is very small (short), and the extra brass is on the outside of the neck, not the inside. It makes for a kind of the inverse of a doughnut. If you are going to turn necks, you need a F/L die to establish a crisp neck.shoulder junction so you can set the cutter to just bite into the shoulder. IMO, if you turn necks sized with a redding bushing die, you'll cut the neck material immediately adjacent to the shoulder way too thin, as it will have a larger OD and ID than the rest of the neck.

No, the height of the bushing is not adjustable, assuming you intend to F/L size with the dies. You can screw the die out a little and "partial F/L size and just size a portion of the neck, but that can lead to some headspace irregularity.

Regarding bushing size, I've found this to be highly dependent on how sloppy your chamber is cut. I'd order one a thousandth under loaded loaded OD and try it. In other words, it depends on the amount of constriction you have to make between a fired case and a loaded round. Say you want 2 thou neck tension but your fired cases are 6 thou over loaded neck OD. That means you have to constrict 8 thou. You may have to do this in two steps. I've found that changing the neck more than about 5 thou in one step leads to high runout.
Good questions, though. Yes, it helps to have uniform brass......
Elkbane

 

[Phil3]

Thank you. Regarding not being concerned about the neck being concentric with the bullet or case, I take that means some neck runout is OK, as long as bullet and case runout were zero. This would happen if the neck wall thickness varied.

It looks to me that the Redding Competition die is a neck sizer only?

I am not sure I understand this. "...The other concern becomes how much clearance you want between the chamber neck and the loaded round. If you turn a couple thousandths off the neck for a factory or no-turn chamber, you'll need to size the neck down five or six or seven thousandths or more each time. It's hard on the neck and more difficult to keep them concentric...".

Please let me know if I have this right, using simple numbers for clarity. The case is fired, the neck seals itself against a chamber .251" in diameter. The brass springs back .001" to a diameter of .250". The neck is resized to a diameter of .246", thereby providing .004" total clearance with the chamber. I neck turn the brass down .002". Now the brass is .244". Fired again, it comes out of the gun at .250". I resize again to .244", which is a reduction of .006", a fairly large change. It seems the only way to maintain a good fit between the chamber and maintain adequate neck tension is to have brass of sufficient thickness. How does one measure the actual chamber diameter and what is a good clearance value?

Thank you.

- Phil

 

[Elkbane]

Almost. You forgot one thing. If your .246 sized neck has .002 neck tenion, then the OD of the neck is .248 with bullet seated. Which leaves 3 thou chamber clearance.

The way to get these measurements as close as possible is to make a dummy round with the brass and bullets you intend to use, then have the rifle built (chamber neck) for 2-3 thousands clearance over the loaded neck OD (by choosing the correct reamer). If the rifle is already built, that choice is already made for you. That only leaves you with choice of brass, WRT neck wall thickness, to address the gap between fired OD and loaded OD. You use bushing selection to affect neck tension once you've done the best you can with brass selection and the inherent dimensions of the chamber.

With good brass, you probably won't take 2 thou off in turning (unless you need to creat chamber clearance)- just enough to even up the necks.
Elkbane

 

[Phil3]

Becoming clearer now. Thank you for your patience.

Could I not determine the diameter of my chamber be measuring the outside diameter of a fired case, and add about .001" for case springback? Or is this just too inaccurate? Cerrosafe sounds fine, but one rifle is an AR15, and it is hard to get to the chamber. Whatever this dimension is would appear to define what brass and wall thickness I need. When you say .004" for an AR, do you mean total clearance, or .004" per side (.008" total)?

To use the Redding bushing die, I have to determine my preferred neck diameter, which means I have to settle on a brass to use, if used in an AR, needs to be something not too pricey, since ARs can beat up brass.

Any disadvantages of the Redding bushing arrangement?

- Phil

 

[GermanS1]

Phil, this topic has been covered well in this thread, but since photos can help and I needed to cover this for my club members anyway, here you go:

http://riflemansjournal.blogspot.com/2009/10/reloading-neck-tension.html

 

[RJinTexas]

Your going to need more then 0.002 neck tension with your AR loads or some of the bullets will end up being driven back into the case neck by the force of the gas operated bolt cycling process. I believe you'll be better off using a std full length die for your AR loads.

Regards
RJ

 

[Phil3]

With an AR, assuming you're feeding from a magazine, I don't know if you'd really want to go to all this trouble. I'm a big AR fan but with all the bangin' and slammin' around the ammo goes through I don't know when you reach the point of diminishing returns. Other guys like Robert Whitley (rcw3 here I believe) or Larry Medler (anyrange I think) can help you a lot more than I can. They both have websites and seem to be very helpful.

I can say that with Lapua 223 brass at almost $60/100 and Winchester at not much over $20 I'd most likely be using Winchester in an AR.

I know the AR manhandles ammo (will be loading from the mag), and probably will not go to great lengths with that rifle much of the time, but do intend to have a 223 Remington bolt or some other precision bolt, and wanted to learn as much about accurate reloading as possible. After attending some benchrest matches, it is apparent having a great rifle is only half the battle...knowing how to make excellent rounds is the other half, plus wind reading, etc.

I have corresponded with Mr. Whitley before and will ask about how far to go to get best accuracy out of the AR. For his 6mmAR, he does offer Redding dies, FL, and micrometer seater, with an optional bushing die if desired. Didn't know about Larry Medler.

Thank you for your help.

- Phil

 

[Phil3]

Your going to need more then 0.002 neck tension with your AR loads or some of the bullets will end up being driven back into the case neck by the force of the gas operated bolt cycling process. I believe you'll be better off using a std full length die for your AR loads.

Regards
RJ

Yes, I see on www.6mmar.com, that Robert Whitley recommends .004" for the 6mmAR. No way you can have modest tension with all the carrying on that goes on inside an AR from a magazine load.

- Phil