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Thread: Odd jam...Any ideas?

  1. #21
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    Quote Originally Posted by BufordTJustice View Post
    I think this is likely it. I encountered a similar "strange" issue a few months back on a buddy's gun. I had him put some Federal 62gr Fusion soft points in the mag (also a Lancer L5 AWM) so I could see if the nose was impacting the feed ramps at and extreme angle or maybe even the front of the magazine. He was using some shit-brand lower but it was the same issue. I could see the nose of each round was smashed to hell (but ti didn't do anything to the nose of the '193 rounds). Didn't happen with USGI mags with MP followers (Brownells mags).

    Also, the L5 AWM's in my experience, apply more pressure on the bottom of the BCG due to their extra-stout mag spring. This could also exacerbate the issue by artificially slowing the Carrier's final stroke, going into battery due to friction of the round body against the interior of the feed lips. I think IG's rec on the Blue spring and H3 buffer may alleviate any issues that are purely related to the Lancer's XP mag spring.
    The Lancer AWM spring and the PMAG Gen III spring on the mags I gutted look literally interchangeable, right down to their "finish".

  2. #22
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    Quote Originally Posted by MistWolf View Post
    This problem may still be short stroking. The bolt not only needs to come back far enough to clear the rim, it needs travel back enough that the bolt gets a running start before it contacts the new round. If the bolt stops just as it clears the rim, it won't have any momentum to strip the next round. Spring pressure alone may not be enough to reliably feed the next round. It will be worse with aluminum mags, especially with steel cased ammo because aluminum mags have more stiction.

    Of course, as you point out, a weak action spring will also cause this issue along with giving the rifle sharper recoil
    -The action spring is within spec, and will strip a round and chamber it when released nearly touching the rim of the round.
    -I cannot possibly believe that a 10.5" gun running a can and an H2 buffer which will also cycle without the can, could possibly be short-stroking.

  3. #23
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    Quote Originally Posted by WS6 View Post
    The Lancer AWM spring and the PMAG Gen III spring on the mags I gutted look literally interchangeable, right down to their "finish".
    I just did a quick experiment. The Lancer AWM's magazine follower required 3.70lbs of pressure to depress the follower .5". The PMAG gen3 I used to compare required 3.25lbs of pressure to compress the follower the same amount. If you subtract the weight of the PMAG gen3 (.32lbs on my digital scale) and the weight of the Lancer AWM (.27lbs), the difference grows slightly....I measured vertically so the weight of the magazine bodies must be accounted for.

    Lancer= 3.43lbs of pressure to depress the follower .5". PMAG = 2.93lbs to depress follower .5".

    Both magazines have exactly 30 rounds through them and were then put away for storage. The difference is not very big, but it could make a difference I suppose. The Gen3 PMAG has a stronger spring than the MOE/RevM.

    EDIT: The springs may very well BE identical...but differences in body geometry and internal space could also be a factor...potentially adding some pre-load to the follower via the spring if the same spring is compressed to a higher static percentage.
    Last edited by BufordTJustice; 08-19-13 at 11:59.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

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  4. #24
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    Quote Originally Posted by BufordTJustice View Post
    I just did a quick experiment. The Lancer AWM's magazine follower required 3.70lbs of pressure to depress the follower .5". The PMAG gen3 I used to compare required 3.25lbs of pressure to compress the follower the same amount. If you subtract the weight of the PMAG gen3 (.32lbs on my digital scale) and the weight of the Lancer AWM (.27lbs), the difference grows slightly....I measured vertically so the weight of the magazine bodies must be accounted for.

    Lancer= 3.43lbs of pressure to depress the follower .5". PMAG = 2.93lbs to depress follower .5".

    Both magazines have exactly 30 rounds through them and were then put away for storage. The difference is not very big, but it could make a difference I suppose. The Gen3 PMAG has a stronger spring than the MOE/RevM.

    EDIT: The springs may very well BE identical...but differences in body geometry and internal space could also be a factor...potentially adding some pre-load to the follower via the spring if the same spring is compressed to a higher static percentage.
    I just don't think that minute difference really matters, and if it did, it would not have showed up half a dozen shots in, but rather on trigger pull #2, or in me not being able to chamber round #1 (or #30, however you want to word it).

  5. #25
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    Quote Originally Posted by WS6 View Post
    I just don't think that minute difference really matters, and if it did, it would not have showed up half a dozen shots in, but rather on trigger pull #2, or in me not being able to chamber round #1 (or #30, however you want to word it).
    I agree the difference is not that big and it might have zero effect on this issue. But the difference in pressure is still almost exactly one half-pound.

    EDIT: Also possibly playing into the freak-incident......the matte finish on the metal feed lips of the AWM could add to the friction on the case as its being fed as opposed to the smooth face of the PMAG's polymer feed lips.
    Last edited by BufordTJustice; 08-19-13 at 12:11.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

  6. #26
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    Quote Originally Posted by BufordTJustice View Post
    I agree the difference is not that big and it might have zero effect on this issue. But the difference in pressure is still almost exactly one half-pound.
    It varies by many many pounds over the course of shooting the entire mag, and malfunctions don't happen all in the first 25% of the mag, IMO/IME. I just don't think it's the issue, here. I think nose-diving is, caused by the lower being funky, and the mag being a bit more sensitive.

  7. #27
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    Quote Originally Posted by WS6 View Post
    It varies by many many pounds over the course of shooting the entire mag, and malfunctions don't happen all in the first 25% of the mag, IMO/IME. I just don't think it's the issue, here. I think nose-diving is, caused by the lower being funky, and the mag being a bit more sensitive.
    Roger that on both counts.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

  8. #28
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    Possibly an out of spec case?

    Keith

  9. #29
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    Quote Originally Posted by Keith E. View Post
    Possibly an out of spec case?

    Keith
    I have had issues on another rifle with this type lower (Gen 2 FFL) and Lancers that could result in this malfunction if the round BARELY made it into the chamber.

    The case ejected and seated in the chamber fine once I cycled it again. I doubt it was out of sped.

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