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No Stretch Sizing Die?

Discussion in 'Handloading and Reloading' started by LubeckTech, Mar 19, 2008.

  1. LubeckTech

    LubeckTech Well-Known Member

    A few weeks ago on TV I saw a demonstration of a sizing die for bottleneck rifle cases that doesn't stretch the case so you don't have to trim cases but I don't remember who makes it or what it is called. Does anyone know about these??
  2. Jim M

    Jim M Active Member

    RBCS X-Die

    That would be the RCBS X-Die. You do have to trim the cases the first time. After that, you just lube the cases and size normally in the X-Die.

    It does cut down on trimming after the first time, and from my limited use of the dies, I seem to get about twice the number of reloads from each case using the X-Die.
  3. ranger335v

    ranger335v Well-Known Member

    Don't think X dies stop stretching, as such, they just push the growth in neck length back into the case, thus displacing the neck brass that shows up with stretching. Still have to watch for web thinning and possible case seperation.
  4. Jim M

    Jim M Active Member

    The RCBS X-Die actually pushes both the case shoulder and the case mouth back down. The case growth that usually causes cases to fail is in the web. That is the weakest part of the case, especially after the first firing. The X-Die pushes the whole top half of the case back down toward the base by whatever amount the case has stretched. Since the web is the weakest part, the brass is extruded back into that area, strengthening the web where it was previsouly stretched.

    That can't go on forever, because I believe the case is weakened a bit each time it is fired. However, the X-Dies seem to give me about twice as many loadings of each case before I have to discard it because of case stretching.

    Cases obviously won't last forever. Webs still stretch a bit, even with the X-Die, and case mouths still split. However, I now use the X-Die on several calibers, and I think they are worthwhile.

    Jim M
  5. Grizzly Adams

    Grizzly Adams Well-Known Member

    Why spend the money on new more expense sizing dies when neck sizing does the same thing?
  6. dmickey

    dmickey Well-Known Member

    Plus the RCBS X-die is only available in certain calibers. They don't have one for .22 BR, 6mm BR and 6mm/250 like I shoot (among others.)
  7. Car Knocker

    Car Knocker Well-Known Member

    Well, necksizing-only may cause problems when reloading for semi-autos.
  8. ranger335v

    ranger335v Well-Known Member

    "The X-Die pushes the whole top half of the case back down toward the base by whatever amount the case has stretched."

    Jim, that's interesting but I don't think it's possible. That requires that pushing back on the neck would have the brass to then expand and flow back into the shoulder and then flow back to and down the body until it reached the web area. I believe the forces involved would be limited to pushing the neck into the shoulder and the brass would stop moving there.
  9. moosehunt

    moosehunt Well-Known Member

    ranger335v is much closer. The stretching doesn't take place in the sizing. The stretching takes place during the firing, and stretching can't be undone. The case stretches in two planes-longitudinal (diameter) and horizontal (length). In sizing, we are returning the diameter to original. The brass has to go somewhere when squeezed back down in diameter, and it can only go where there is a release, i.e. toward the neck. Thus, the case lengthens additionally, but this is not stretching, and we have not removed the stretch that occurred, only relocated the brass to the only place it can go, the free end (neck). One approach is to trim this excess length. The other, the X die simply folds the extended neck down into the shoulder. The brass is not, cannot be "compacted". In using an X die, the loss of brass in the web area occurs at the same rate as any other method of sizing; indeed, it needs to be understood that it is not the sizing that effects the web, but the stretching that took place in firing. There is no gain in this aspect by using an X die. The X die is conducive to simplified loading, but is NOT conducive to accurate loading. It actually increases work fatigue (hardening) to the shoulder area. If one must FL size, i.e. for a semi-auto, then he should perhaps accept trimming as a necessary evil. The longest case life will result from taking once fired brass (from your gun), trimming, then using only neck sizing as long as possible (usually 5-7 loadings), then anneal the necks, FL size, trim the necks, and begin the neck sizing sequence again. Normally, it will not be necessary to trim cases between the FL sizings, only when you perform the anneal/FL step. Using this approach, the eventual demise of the case will be at the web. You will not have split necks and you will maintain rather consistant neck tension. Obviously then, one must pay particular attention to the web area for eventual exhaustion, as the neck will normally not fail. An X die will lead to failure in the neck/shoulder region in due time. If you anneal this area periodically, you will prolong case life, but then you will need to trim. The X die is OK if case life and accuracy are not of great concern. It is OK if it satisfies you, but it is not really a good approach if you are concerned with accuracy. Since semi-autos, in general, aren't known for accuracy, it probably isn't a bad combination, but case life will not be maximized, by a good bit. While the X die basically "works", it is a shortcut that you pay for, pretty significantly in my opinion. But as stated, it may well be justifyable in a semi-auto. I'm not opposed to the X die, though it's not for me, but I think it is important for a guy to know what it does and doesn't do and how.
  10. Jim M

    Jim M Active Member

    Most cartridges don’t fit exactly in the chamber. Before firing, there will be a few thousandths of an inch of space, either between the shoulder of the case and the shoulder of the chamber, or between the base of the cartridge and the bolt of the gun. Usually, when the firing pin strikes the primer, that forces the cartridge fully forward so that the shoulder of the cartridge is firmly against the shoulder of the chamber. When the powder ignites and the pressure builds up, the powder gas expands the case against the chamber walls. The expanded case will stick to the chamber walls, while the case head will be free to move back a few thousandths of an inch until it is firmly against the bolt. That differential movement of the cartridge head away from the body of the cartridge is what causes the stretching of the cartridge case. That stretching occurs just above the head of the case, in the thin area commonly known as the web.

    One thing that happens when a case is full-length sized is that the case neck and the body of the case are reduced to their former diameters to restore the case to the diameter it had before firing. That works the same in an X-Die as in a standard sizing die. Full length sizing dies (and X-Dies) will also restore the cartridge length, as measured from the base of the case to the shoulder of the case, to its original length to facilitate easier chambering of the loaded round. Neck sizing dies, of course, only restore the original diameter of the neck, and do not size the body of the case or push the shoulder back to compensate for any case stretch that occurred on firing.

    In restoring the original length of a cartridge case, as measured from the base to the shoulder of the case, the standard resizing die will operate on the easiest part of the case to modify. The web is larger in diameter and will resist any compression of the brass at that point, so the full-length sizing die will usually push the shoulder back by whatever amount the case has stretched in firing. The dimension from the base to the shoulder of the case will be correct, and any excess brass will result in a longer neck. That neck is usually shortened by trimming to return the case to the proper “trim-to” length.

    The X-Die has a mandrel which, in operation (after the first trimming of the cases), will bear firmly against the case mouth when the case is inserted all the way into the X-Die sizing die. This mandrel prevents the X-Die from pushing the shoulder back to restore the original base-to-shoulder dimension. Instead, the mandrel bears down on the case at the mouth, while the shoulder of the X-Die is bearing down on the shoulder of the case. Meanwhile, the body of the case is firmly supported by the body of the sizing die. The result is that the entire body of the case – neck, shoulder and body of the case, all the way down to the web – is pushed down toward the head of the case. The excess length, which on firing has gone to stretch the case at the web, is now taken up by the extrusion of the brass back into the web area, shortening the case to its original length and somewhat thickening the web where it was previously thinned on firing.

    The net effect of using the X-Die is that the brass is extruded back into the web area, exactly from where it came to stretch the case in the first place. There is no great movement of brass from the neck to the shoulder to the body of the case. Rather, the length of the case is simply restored by compressing the top part of the case (everything above the web) AS A UNIT back down toward the case head, and the excess brass extrudes back where it came from – the web.

    I don’t work for RCBS. I don’t have any interest in the sale of RCBS dies. I’m just a shooter who has been reloading rifle cases for more than 40 years, and I’m trying to pass along some information that I thought might be responsive to the question posted by the original member on this thread.

    I have used conventional dies, neck sizing dies, and RCBS X-Dies. I think there is a place for all of them. I don’t mind passing along my observations to other members who might be interested. My advice is probably worth exactly what you paid for it here. If you find it useful, use it.

    Jim M
  11. Idano

    Idano Well-Known Member

    Great write up Jim. I have been a firm believer of the RCBS X-Die technology.
  12. rbernie

    rbernie Well-Known Member

    Test this hypothesis, and measure your cases before and after sizing. What you'll find is that very little growth occurs as a function of sizing. Ergo, almost all case growth occurs during firing.

    Also bear in mind that the case isn't actually resized completely to its original diameter when resized; the base and web are normally left untouched.
  13. ranger335v

    ranger335v Well-Known Member

  14. ranger335v

    ranger335v Well-Known Member

    Jim, not trying to make an issue of this but I started reloading in '65 and have not only done it, I've studied it from a mechanical engineering point of view. There is no physical way that pushing back on the mouth of a rifle case can restore or re-thicken the stretch-thinned brass above the web. The pushing back effect will simply stop at the neck to shoulder juncton.
  15. Jim M

    Jim M Active Member

    ranger, that's an interesting coincidence. We started reloading the same year, 1965.

    I used conventional sizing dies for most of those years. I also use neck size dies for a couple of calibers, and for others, I simply back the sizing die out one turn and use that to neck size. Neck sizing only works if your gun has a tight lock-up and the loads are fairly mild. That's no criticism of neck sizing, only an observation that it doesn't work all of the time. I realize that you know that, but I am only mentioning it for the newer reloaders.

    As for the X Dies:

    The neck is not pushed back into the shoulder junction. The top part of the case looks (and measures) the same after sizing, as far as length goes. The diameter is reduced. The "pushing back effect" DOES NOT stop at the neck to shoulder junction. The case length difference is at the web.

    With full power loads, particularly those fired in semi-automatic rifles, my brass usually fails first at the web. I get the characteristic bright ring around the case at the web, and with a bent wire probe (a reformed spring hook) slid along the inside of the case at the web, I can feel the thin area of the web at the same point on the case as the bright ring appears on the outside of the case. That's time to discard the case, because I know I will get case separations if I continue to reload those cases, even after conventional resizing and trimming to length.

    Using the X Die, I can generally reload the case about twice as many times as with the conventional sizing die. They still thin at the web, but just not as fast. In fact, case mouth splits become a factor when the brass has been fired enough. With conventional sizing dies, I toss the cases because of thin webs and incipient case separations (and actual case separations if I load them one or two more times) long before the case neck splits show up.

    One of my M1As seems to have a "springy" action, although the headspace measures within specs. Cases fired in that rifle will develop the bright ring at the web after only two or three reloads with conventional dies. With the X Die, I get about twice as many reloads before I toss the brass. I have had enough complete case separations with that rifle using conventional sizing dies (also RCBS) to know not to continue to use stretched brass. But again, with the X Die, I get double the case life.

    I can see the difference in the bright ring at the web using the X Die. I can also feel the difference on the inside with the spring hook. I have cut stretched cases lengthwise and noted the differences on the inside of the cases that have the bright ring.

    My personal experience has been that the X Die extends case life. The difference is at the web. There is no difference at the neck to shoulder junction, and the neck is not pushed back into the shoulder.

    I will continue to use the X Dies for those calibers for which I have the dies. Maybe others will have different experiences, but I recommend the dies.

    As I said before, I don't work for RCBS, and I have no financial interest in the company (other than that I have bought a hell of a lot of their dies over the years). I wouldn't try to talk anyone else into using the X Dies.

    I do recommend them. After that, each reloader has to make his own decisions.

    Thanks for your courteous replies.

    Jim M
  16. stubbicatt

    stubbicatt Well-Known Member

    I don't know how it works, but I KNOW the X Die works. It helps if you use good case lube and lube the insides of the case necks to keep the expander ball from torquing the necks on its way out.
  17. ranger335v

    ranger335v Well-Known Member

    Hey Jim, so you and I started in different places together! Great, keep it up. How did we ever survive reloading back in those distant and "primitive" days?

    We had no confusing (and usually irrelivant) OAL figgers in our manuals, no internet to ask for spoon feeding on the "best" caliber-powder-tumbling media-bullet-dies/press-etc, no viberating case tumblers, no electric gismos to dispense and weigh powder. Few if any us had micrometers or dial calipers, there were no affordable chronographs with direct speed read-outs, no store bought gadgets to find the origin of the chamber rifling, etc., all things today's loaders seem to think are mandatory for safe reloading! In those days, each of us simply had to experiment, think and observe for ourselves what worked best in our rigs! ;)
  18. moosehunt

    moosehunt Well-Known Member

    Boy, I sure second what ranger just said! I guess some would call us "old timers". I reckon I precede you guys by about 3-4 years, which means nothing. Jim, as ranger says, it is not possible to "unstretch" the stretching in the web by forcing the metal back to greater thickness. The X die cannot repair the damage done at the web-to-body juncture during firing. This has been corroborrated by RCBS. May I refer you to "Understanding Case Deformation" by M. L. McPherson, Varmint Hunter Magazine, Jan. 2002, Issue #41, pp 92-95. It is a very good piece of material.
  19. Jim M

    Jim M Active Member

    Interesting discussion. I’ve learned a lot.

    I agree with ranger335v that, as he said in post #3, the X dies don’t stop case stretching. We still have to watch for web thinning and case separation. We seem to either disagree or be stating differently where the growth in case length is going when we size in an X Die.

    I also agree with moosehunt (and rbernie) that the stretching doesn't take place in the sizing; it takes place during the firing. SOME of the stretching does seem to be undone by sizing in the X Die. I don’t believe that the X Die “simply folds the extended neck down into the shoulder”, as moosehunt contends in post #9. The mandrel in the X Die prevents the neck from lengthening, and the shoulder of the X Die prevents the neck from being “folded” down into the shoulder. Thus, the brass displaced to cause the case to stretch at the web has to go to the only place left, back to the web. I certainly recognize that both ranger335v and moosehunt disagree with that conclusion.

    moosehunt also has great advice on reloading with neck sizing only as long as possible. (See post #9.) I use a similar procedure when loading milder loads for bolt action rifles. Unfortunately, with full power loads in bolt action rifles, particularly when the reloads are to be used for hunting, or with autoloaders, I don’t get the required 100% smooth and fast functioning with neck sized ammunition.

    I don’t see any evidence of work hardening in the shoulder area of any brass when loaded with the X Dies. That brass usually fails because of web stretching and thinning (although after more reloads than with conventional sizing dies) or from case neck splits. Again, moosehunt is correct that annealing the brass will prevent most of the case neck splits. I still get split necks occasionally, and I just attribute it to the fact that I was too lazy to anneal the necks in that lot of brass. Usually, though, the webs fail before the case necks, even with the X Die.

    I don’t accept neck length trimming as a necessary evil. The X Die eliminates that, even with full length sizing on every reloading.

    moosehunt, that article that you cited sounds very interesting and on point. I don’t have a copy and don’t have access toVarmint Hunter Magazine. Is that article, by any chance, available on the Internet?

    Although the X Die increases the life of the brass enough to be worthwhile to me, it still won’t last forever. Several other members who have posted on this thread also have good luck with the X Die. I think we have done the best we can to get the information out there, and now each reloader has to make his own decision whether or not to use the X Dies.

    Jim M
  20. moosehunt

    moosehunt Well-Known Member

    Jim, the only way I know to get you the article is if you want to forward your address to me, I'll copy it and send it to you. It may be available on the internet, don't know. You might try www.varminthunter.org They have writers that produce researched articles that go into the depths of reloading and shooting that will blow a science oriented persons mind. On some of their articles, they get DEEP! And it is research backed.

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