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How to jam an AR-15 in one easy step

Discussion in 'Handloading and Reloading' started by strat81, Mar 10, 2008.

  1. strat81

    strat81 Well-Known Member

    Make sure your Lee Crimp Die is adjusted for a HEAVY crimp. This will bulge the shoulder and when you go to chamber the round, you'll get a nice ol' jam. Nothing like slamming your rifle against the bench to fix it. LOL :banghead::cuss::fire:

    How does this happen since it isn't the crimp itself that causes the problem? Well, look at how a Lee rifle crimp die works. As you raise the ram, the cartridge enters the "jaws" of the die and the ram itself presses on the bottom of the die. The bottom of the die then compresses those jaws. Since I was crimping heavily, the case was held stationary by the jaws while the ram kept pushing up on the base, resulting in the bulge at the shoulder.

    Since the shoulder was bulged, it was bigger than the front portion of the chamber and attempting to load the round wedged it in there darn good.

    I'll still be using my crimp die, but I have backed off the tension.

    Moral of the story: don't crimp too heavy and inspect your rounds carefully!

    On the plus side, informal accuracy tests showed that my reloads (24.5gr H335, 55gr FMJBT, 2.240 OAL) were more accurate than the cheap Remington UMC 55gr FMJ stuff from Walmart and some old boxes of PMP 55gr FMJ.
  2. LexDiamonds

    LexDiamonds Well-Known Member

    Hmmmm. It sounds like your sizing die might not be adjusted to fully size the neck. This could happen in either a full length die or a neck only die. Unless it gets sized down to very near where the shoulder starts, it could create a bulge. Having used the factory crimp die extensively, it sounds odd to imagine applying enough crimp to create a chambering issue. You would have deformed the bullet and then some by that point.
  3. jmorris

    jmorris Well-Known Member

    Thats why they make case gauges.
  4. strat81

    strat81 Well-Known Member

    That was my first thought. When I discovered the problem, I mic'd the brass at every step and at multiple points. Depending on how much pressure I applied while crimping, that is what flared the shoulder. After FL sizing, the brass was all very uniform. A few dummy rounds that I made without crimping slid into the chamber just fine. Not all of the rounds I had crimped were bad since I had varied the pressure on the handle while crimping.

    The way I had the die set up, I was essentially holding the case in place by the mouth using the crimp "jaws" and then pushing up on the case using the ram.

    After pulling the deformed rounds down, I didn't notice any significant damage to the pulled bullets since I was crimping to the cannelure.

    Just glad I figured out what was going on.
  5. kelbro

    kelbro Well-Known Member

    A light crimp is all that is needed.
  6. rcmodel

    rcmodel Member in memoriam

    I have done the same thing when crimping un-trimmed .223 in the regular seating/crimping die.

    I wouldn't have thought it possible with the Lee FCD.

    That must have been some heavy-duty crimping!

    Well, That right there might be your problem!

    Any die works best if you adjust them so the ram always bottoms out at full stroke.

    If it doesn't, all kinds of bad things can happen!

  7. ftierson

    ftierson Member.

    There may have been another problem with the Lee FCD...

    Often, after trimming the cartridge case and deburring the mouth, there's still somewhat of a burr left...

    When you go to use the FCD and you're lowering the press handle to raise the ram, this burr can sometimes catch on the bottom of the neck 'hole' in the collet instead of going all the way up. If it goes all the way up, no problem... The case is held securely in the collet with no pressuire on the shoulder (assuming that the case has been FL resized correctly, of course), and the 'petals' of the collet can squeeze the case mouth from the sides and crimp the bullet in place. However, if the mouth of the case catches on the bottom of the neck 'hole' in the crimping insert, the neck will be pushed down into the case, certainly expanding the shoulder somewhat.

    I ran into this problem after crimping a few thousand rounds of 7.62x51mm NATO with the FCD. It took me a few minutes to figure out what was happening, because the problem would only occur once in a while. Since you tend to crimp fast once you get your cadence established, the problem occurs before you notice it.

    Now, I make sure that the crimping insert is clean and that it moves freely in the die body. I also wiggle the cartridge a little as I'm raising it into the neck portion of the collet. This tends to let any burr slide past the catch point and on up into the neck. I also watch the bullet/neck as it rises in the collet, making sure that it's all the way up before the crimping begins...

    Since adopting this method, I've never pushed the neck back again...

    Good luck in fixing your problem. First, as mentioned above, make sure that the case is FL sized correctly. Then check for neck hangups in the FCD collet as I mentioned...


    ADKWOODSMAN Well-Known Member

    Back, too many years to remember, that how my first .270 Winchester round came out of a regular crimping die. It wouldn't chamber. After looking at it and running it around in my hands, I realized that the shoulder was bigger around than the rest of the case. It was an easy fix to back off the seating die. Since that day, I never crimped a rifle round.
  9. nicholst55

    nicholst55 Well-Known Member

    Crimp? I've never crimped one single round of ammo that I've fired in an AR-15. The government doesn't crimp 5.56 ammo either; there's simply no need to. The same goes for the M1 Garand and M1A or (M14).

    I'm sorry, but the Lee Factory Crimp die, IMHO, is a solution in search of a problem, at least for 99% of rifle cartridges.
  10. ny32182

    ny32182 Well-Known Member

    All the milspec 5.56 I've ever seen has been crimped...
  11. ny32182

    ny32182 Well-Known Member

    That said, I had a very similar jam in an AR15 when shooting my first batch of .223 reloads, and the problem turned out to be not enough sizing going on. I did apply a light crimp to those loads, but that wasn't it. I checked some resized brass in the cartridge gauge, and every one of them was over max.

    Have you checked your resized brass or finished rounds in a gauge? I got the LE Wilson go/no go gauge for about 20 bucks, and it serves my purpose fine so far.
  12. amlevin

    amlevin Well-Known Member

    I "gauge" all my .223 rounds and have had this happen a couple of times anyway. In my case it was caused by some long cases.

    Mine got so tightly jammed I had to pry the bolt carrier back through the ejection port using a screwdriver.

    All cases get trimmed now as necessary before loading.

    nicholst55-- Not only have I seen a lot of crimped M-193 and M-855 ammo, most of it also has a sealer that acts like a "glue" to keep the bullet from moving. Most of the 30-06 and .308 milsurp I have "pulled down" has all had the same or similar sealer. The bullets may not be crimped but for all practical purposes they are glued in place.
  13. flynlr

    flynlr Well-Known Member

    every gov 5.56 round from win or LC I have ever seen had a crimp on it
  14. Doug b

    Doug b Well-Known Member

    Collet dies

    strat81 Compound linkage and collet style dies don't mix well at all.
  15. Uncle Chan

    Uncle Chan Well-Known Member

    Same problem here. Just back the FCD out and put a LIGHT crimp on it and you'll be fine. I've done the same thing several times. I pull the bullet. Pop out the primer. Resize the brass. Reload it again. Now the crimp is so light that it is practically non-existent.

  16. David Wile

    David Wile Well-Known Member

    Hey folks,

    I think nicholst55 makes an interesting and largely valid point when he suggests the Lee Factory Crimp die "is a solution in search of a problem, at least for 99% of rifle cartridges." I don't use hot loads, so none of my bullets move because of recoil. If my full length sizing is good enough to keep the bullets from moving under recoil, I don't see the need for crimping.

    Best wishes,
    Dave Wile
  17. rodregier

    rodregier Well-Known Member

    Projectiles can also be pushed into the case body by feed ramps in a semi-auto, not just recoil. That will really run up the pressures :-(
  18. David Wile

    David Wile Well-Known Member

    Hey Rodregier,

    While I have only ever used jacketed bullets for my AR-15, I have never crimped my loads, and I have never had any bullets pushed into the case body after being chambered. This can be easily checked by loading a mag in the rifle, shooting a round, pulling the mag, removing the chambered round and inspecting overall length. Like I said before, I do full length resize all my auto loading cases, and that may be a factor.

    As to other auto loaders, I have several rifles in 7.62X39 (AR-15, several Russian SKS, and a Ruger Mini 30), and I use both cast and jacketed bullets in all. Again, I full length resize, load bullets without crimp, and I have never had a problem with bullets moving under recoil or from the feeding process.

    Best wishes,
    Dave Wile

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