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need help with 223 loading problem

Discussion in 'Handloading and Reloading' started by cemjr, Oct 7, 2011.

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  1. cemjr

    cemjr Member

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    I need help solving a problem. The problem is my rounds getting .004" longer after chambering in my AR. I'm using once fired FC brass, all preped , cleaned and full length sized. The bullet is a 69gr sierra MK HPBT. The first test loads with no crimp "grew" .007 , so I started adding taper crimp, even with significant crimp, they get .004 longer when the bolt drops:banghead: I don't have a problem with them getting shorter under recoil forces. I disassembled a crimped round and measured how much crimp, .004 . I done alot of reading already from multiple referance matl., no answer yet:mad:
     
  2. rcmodel

    rcmodel Member in memoriam

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    Check your expander plug.
    Sounds like maybe not enough case neck tension.

    The expander should measure at least .002"-.003" under bullet dia.

    Also check for sizing lube being left inside the case necks.

    Recoil forces does not shorten light recoiling rounds in the magazine.
    Feeding and banging into feed ramps and barrel extensions might.

    At any rate, check the expander, clean the case necks dry of lube,
    and crimp to the back edge of the bullet cannulure, not the front edge.

    If the rear of the bullet cannulure is already in contact with the crimp,
    they can't hardly grow anymore on you just from chambering force inertia.

    rc
     
  3. 243winxb

    243winxb Member

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    Neck Tension from Sierra

    http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm Neck Tension

    When we stop to consider the vigorous (read, downright violent) chambering cycle a loaded round endures in a Service Rifle, it becomes pretty clear it suffers abuse that would never happen in a bolt-action. This is simply the nature of the beast. It needs to be dealt with since there is no way around it.

    There are two distinctly different forces that need to be considered: those that force the bullet deeper into the case, and those that pull it out of the case. When the round is stripped from the magazine and launched up the feed ramp, any resistance encountered by the bullet risks having it set back deeper into the case. Due to the abrupt stop the cartridge makes when the shoulder slams to a halt against the chamber, inertia dictates that the bullet will continue to move forward. This is exactly the same principle a kinetic bullet puller operates on, and it works within a chamber as well. Some years ago, we decided to examine this phenomenon more closely. During tests here at Sierra’s range, we chambered a variety of factory Match ammunition in an AR-15 rifle. This ammunition was from one of the most popular brands in use today, loaded with Sierra’s 69 grain MatchKing bullet. To conduct the test, we chambered individual rounds by inserting them into the magazines and manually releasing the bolt. We then repeated the tests by loading two rounds into the magazine, chambering and firing the first, and then extracting and measuring the second round. This eliminated any potential variation caused by the difference between a bolt that had been released from an open position (first round in the magazine) and those subsequent rounds that were chambered by the normal semi-automatic operation of the rifle. Measuring the rounds before chambering and then re-measuring after they were carefully extracted resulted in an average increase of three thousandths (0.003") of forward bullet movement. Some individual rounds showed up to seven thousandths (0.007") movement. Please bear in mind that these results were with factory ammunition, normally having a higher bullet pull than handloaded ammunition.

    To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension. The first option, crimping, brings up some other issues that can be troublesome. In general, crimping degrades accuracy. Most match bullets are not cannelured (which also seriously damages accuracy potential), a requirement for correct application of most crimps. Still, there are taper crimp dies available from most of the major manufacturers. Lee offers their “Factory Crimp” die as an alternative, which seems to be one of the better options for those bullets without a cannelure. That having been said, crimping is still, at best, an occasionally necessary evil. Avoid it if at all possible.

    The other—and in our opinion, better—option is increased neck tension. This, in turn, leaves us with two more options depending on what type of equipment you’re using. The object of either is simply a tighter grip on the bullet. Using conventional sizing dies, (i.e., those utilizing an expander ball) this is accomplished by reducing the diameter of the ball itself. This can be done by chucking the expander/decapping rod into a drill and turning it down slightly with fine emery cloth or a stone. The goal here is to decrease the diameter two or three thousandths (0.002" to 0.003") under bullet diameter. This is a trial and error process, and must be done slowly. The end result is an expander ball that opens the case neck up somewhat less than the as-issued item. This, in turn, increases the grip of the case neck on the seated bullet.

    A better alternative to achieve the same effect is the use of a bushing die, such as those from Redding Reloading. This is by far the best solution, not just for Service Rifles, but for a broad range of reloading applications. The basis for this system is a fairly conventional sizing die, at least where the body and shoulder of the case is concerned. In the neck area, however, the die is fitted with a removable bushing. Available in .001" increments (as measured at the inside diameter of the bushing), they can be matched with a specific batch of brass to provide optimum neck tension. This tension can be increased or decreased by simply moving up or down in bushing size. The one drawback to this system, if it can be called a drawback, is the absolute necessity of sorting cases and loading them in batches. This, of course, is how virtually all loading should be done anyway.
     
  4. cemjr

    cemjr Member

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    243winxb, I got that exterior ballistics saved to my favorites alread. rc , these bulltes don't have a cannulure but I'll try checking the lube in the neck thing. I was carefull not to use too much lube and I had the cases on there sides when I sprayed them. I'll measure the ball too.
     
  5. cemjr

    cemjr Member

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    ball measures .223, bullet .224, bingo :banghead: so how sucessful has anyone been with the hone stone method:confused:
     
  6. cfullgraf

    cfullgraf Member

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    Should be no problem using a stone as long as the expander is steel. A bit more difficult if you have one of Redding's carbide expanders.

    I would prefer to use emory cloth polishing with 400 grit or finer at the end. But a stone would work as well.
     
  7. cemjr

    cemjr Member

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    the reason I thought stone is, the expander is more barrel shaped and a stone would retain the flatness of the diameter.
     
  8. cfullgraf

    cfullgraf Member

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    Wrap the emory cloth around something flat.

    But a stone will work as well. The prime objective is to go slow so that you don't remove to much.
     
  9. zeke

    zeke Member

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    Anymore, i don't use use the expanding plug at all and use a redding comp seater.
     
  10. FROGO207

    FROGO207 Member

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    Yep use a stone or emery cloth on a small piece of bar stock or such. Make sure you move it up and down on the expander button to remove the material evenly on the outside radius. Do measure often as it is hard to put back once the steel is removed.:D I do this on most of my dies before using them the first time now.
     
  11. beatledog7

    beatledog7 Member

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    How do you know if the neck tension is too great? Using a neck sizing die with .223 can result in an inner neck diameter that's so small you can barely get the bullet started. Is that what we're after?
     
  12. cemjr

    cemjr Member

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    I don't think reducing the id of the case neck by .002 will interfere with getting the bullet started because I'm using hpbt bullets
     
    Last edited: Oct 8, 2011
  13. W.E.G.

    W.E.G. Member

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    How about this for an answer: So what?

    When you chamber a round, you intend to shoot it, right?
    So, drop the hammer on it, and collect your brass.

    ...or you can jack it out of the chamber and measure it with a caliper.

    Tell me how this 0.004" bullet jump is an issue.
     
  14. cemjr

    cemjr Member

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    I don't know that is is an issue. I did measure the bullet after chambering that's how I know it's getting longer. I also fired a dozen to test the powder charge and they all went bang.
     
  15. rcmodel

    rcmodel Member in memoriam

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    But, you said in your first post you were crimping them??

    Crimping a bullet without a cannulure can actually make a bullet looser, not tighter.

    The reason is, the soft lead core compresses under "the crimp with no place to go", and stays compressed, while the harder jacket springs back a little.

    rc
     
  16. 243winxb

    243winxb Member

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    Thinning of Case Necks.

    The case neck wall thickness has a lot to do with neck tension. Undersize or thin necks will not let the full length die size the neck down far enough. If this is happening, the size/diameter of the expander will not matter. Its possible for standard dies to over work the brass, thinning the necks. Having only seen it 1 time, but it can happen when new brass is running at maximum neck wall thickness. Do a test. FL size without the expander, measure. Fl size with the expander,measure. The outside diameter should have increased, gotten larger using the expander. After the bullet is seated, measure the neck again, the diameter should be about .002" larger after bullet seating. Military 5.56 ammo requires a bullet pull of 35 to 45 lbs.
     
  17. cemjr

    cemjr Member

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    "To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension. The first option, crimping, brings up some other issues that can be troublesome. In general, crimping degrades accuracy. Most match bullets are not cannelured (which also seriously damages accuracy potential), a requirement for correct application of most crimps. Still, there are taper crimp dies available from most of the major manufacturers. Lee offers their “Factory Crimp” die as an alternative, which seems to be one of the better options for those bullets without a cannelure."

    As I said in my OP, with no crimp the cartridge got .007 longer, the taper crimp reduced that amount by .003. The bullets are Match Kings.

    No luck trying to reduce the size of the expander ball, must be hardened steel or carbide. I'll call Dillon monday to see if they have smaller sizes
     
  18. cfullgraf

    cfullgraf Member

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    Yes, Dillon expander buttons are carbide.
     
  19. jelenko

    jelenko Member

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    win243xb,

    Nice to see some actual data!

    But, what difference does 3/1000 to 7/1000 make when feeding from a mag? The bullet is already several hundreths from the lands.

    Thanks

    PS. Just read WEG's comments. Guess I completely agree with WEG.
     
  20. cemjr

    cemjr Member

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    Well, I not certain is does make a differance, "the round getting longer that is" but I think consistency from one round to the next "might" sufer
     
  21. 243winxb

    243winxb Member

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    Bullet Movement on Chambering.

    Bullet movement shows there is a condition that needs to be addressed. What if the next round has even less neck tension? Lets say the base of the bullet is no longer in contact with the case mouth. The rifling has not stoped the bullets forward movement (very long throat). On firing, no pressure will be produced to burn the powder correctly. Gas will be vented back past the neck that did not expand. There will be a puff/cloud of dark smoke coming from the action. The bullet may or many not clear the barrel. Lets say the bullet is lodged in the barrel. The case did not eject on firing. The shooter works the action, chambering another round. Using the forward assist, forces the round into the chamber. Pulls the trigger-KABOOM Could this happen? Yes or No ? :D
     
  22. snuffy

    snuffy Member

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    SO WHAT? Geeze, neck tension is the basis of consistent powder burning. Without good neck tension, you get poor ignition consistency. Ever hear of a hangfire? The old click----bang? Caused by the primer firing, driving the bullet out of the case BEFORE the powder has a chance to get burning. Then the bullet runs into the throat/leade, stops, THEN the powder gets burning. It can cause excess pressure in an otherwise normal load.

    cemjr, do you have any diamond hones? Diamond will cut carbide quite well, but slowly. You can get cheap ones at harbor freight.
     
  23. cemjr

    cemjr Member

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    243winxb. snuffy, thanks for your input, I'll get this thing figured out before I proceed, that's for sure. Here,s another wrinkel for concideration, after chambering and ejecting the round for measurment, I noticed the firing pin had left a mark on the primer. The primers are seated correctly. Could my buffer spring be closing the bolt with a little too much force, just a thought.
     
  24. cfullgraf

    cfullgraf Member

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    This is a normal occurrence with semi-auto military style rifles with floating firing pins.

    It is one of the reasons that it is so important to seat primers properly for semi-auto rifles.

    Some primers are less sensitive being made similar to military spec primers. CCI #34 and #41 are two examples. Some folks prefer to use them, which is fine. Many have not had problems with regular commercial primers if the primers are seated correctly.

    Also, the floating firing pin is the reason many recommend only chambering a round from the magazine, as opposed to dropping a round in the chamber and letting the bolt snap close on the round. Stripping the round from the magazine slows the bold down just a bit.

    This is difficult or cumbersome when single loading an AR though. The AR is a bit more forgiving in this respect, but it is more important to load from the magazine with an M1 or M1A.
     
  25. Montana Griz

    Montana Griz Member

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    re the 5.56x45/some handloading questions.

    After a 10 year "hiatus'" from handloading I am getting back into it....among many reasons,..one being I have put together an AR 15 in the last few weeks and look forward to having "some fun with it". Being in my 80th year, I'll be doin' a lot of target shooting & also get rid of some "pests" that are around the place--(ground squirrels, skunks, magpies etc.) Livin' out in boonies as I do, I have a 100 yd range set up.......(previously loaded for: .243; 22/250; .30/06; .338 & .375 H&H in my big game huntin' days.).

    The LMT UPPER has a Med/Hvy 20 inch Stainless barrel stamped: "NATO 5.56x45 1/8 S.S". equipped with a 12" Midwest Industries Quad Rail F.F. Forearm. & topped with a 4.5 - 14 x 40 medium quality scope.......LOWER is by CMMG with a R.R. 2 stage trigger and a Magpul ACS Stock.

    I have various bullets weights left over from when I was loading for the 22/250 (including about 1000 Remington 55gr FMJ (w/ a "concave" base AND a cannelure). I don't think they are mfg any more.) They "mike out" at: .2245 with my "MITUTOYO" "4-place" micrometer ( .0000 ).....The other bullets I have (Sierra & Hornaday) all mike-out at .2240 ----except the Hornaday 75gr A-MAX that are at .2242.

    Here is my concern ( and thus some questions):

    My brand new : LEE "Pacesetter" 3 Die Set has an "expander" that reads exactly at: .2232.............thus a difference of: .0013 for the 55gr Rem FMJ.
    With "proper case preparation" this should give adequate neck tension...I think.

    For the 75gr A-Max BT difference is exactly : .0010.....maybe, maybe not enough neck tension...
    (I know I can't load these to fit in the mazagine, so I'm going to load them out to be about .015 "off from the lands" and shoot them "single-shot style'...

    ........(NOTE: I am aware of the lomger "leade & throat (freebore)" in the 5.56x45 vs the Rem .223.
    ......i.e.: 5.56 having--.1620 leade & .0560 freebore--vs .0850 leade & .0680 freebore for the Rem .223 (Source: "Gunsmithing the AR by Pat Sweeney & SAAMI Data)

    But for the other 55gr Horn & Sierra the difference is just .0008.......thus most likely this will be insufficient tension..

    Soooooooooooo, what if I properly and carefully use the "Taper Crimp Die" that comes with the Lee "Pacesetter" 3 Die set on those bullets that may not have sufficient "neck-tension" with the .0008 difference. Thus the taper crimp giving "adequate and consistant" "bullet-release"??

    I am completely open to ALL comments, suggestions and "tips".

    Thanks.

    Edit: The 1000 Rem bullets are:...55gr HP with a "concave base & a cannelure".
     
    Last edited: Oct 9, 2011
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