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Thread: Usgi mag issues

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  1. #11
    Join Date
    29th August 2017
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    Quote Originally Posted by douglas34474 View Post
    First off, springs don't "get weak." Springs fail by breaking. When was the last time you changed the valve springs in your cars engine? Gun springs are no different. Springs a routinely formed "long" and compress on the first use. They take a "set" but this is under 1.0% of the springs working length.
    Actually, springs can weaken with repetitive flexing. It depends on how close they are strained to their limits of elasticity.

    Many springs do retain their spring rate over long periods of time with repetitive flexing. The springs in weight scales are a good example. But like engine valve springs, these springs start out with an uncompressed free length that is only marginally longer than their compressed length. So they operate well within their limits of elasticity.

    Recoil and magazine springs start out with a free length that is much larger than their compressed length. So they operate much closer to their elastic limits. With lots and lots of use, these springs will noticeably weaken.

    Quote Originally Posted by douglas34474 View Post
    As to the differing spring length and number of coils, measure the diameter of the spring's wire. You can get the same spring rate with fewer coils of a heaver wire.
    Spring rate is directly related to the coil wire cross sectional area, but it is inversely related to the number of coils; more coils, lower spring rate.

    To maintain the same spring rate with heavier wire, you would need more coils.

    -

  2. #12
    Join Date
    28th December 2007
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    Although the springs work close to their elastic limit, there is little chance that they will be worked beyond that elastic limit. The compression is limited by the either the magazine or the slide/frame. If springs got weaker with use, Hookes Law would not hold true. There is no time element to the law. W1 = L1, W2 = L2, etc. W = weight or force applied to the spring, L - stretch or compression of the spring. This holds true until the spring breaks.

    You may be right on the spring rate. It's been a while. However, the story is still the same as to the different number of coils and wire diameter.

  3. #13
    Join Date
    29th August 2017
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    And yet, recoil and magazine springs do suffer a reduction in free length with use. Indeed this is used as an indication that the spring needs to be replaced.

    This would only happen if the spring was strained beyond it's elastic limit, or suffered some type of fatigue.

    Perhaps the spring rate of the shortened spring is the same. I suspect the spring rate doesn't fall in proportion to the length reduction, and may very well be similar to that of the new spring. But even so, if the free length is shorter, then the compressed tension will be less.

    So even if the spring rate has not decreased, the operating tension may very well have.

    (edited)

    -
    Last edited by megafiddle; 19th August 2018 at 22:36.


  4. #14
    Join Date
    11th August 2018
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    The mag I threw one of the Wolff extra power springs, an extra from one of my 10mm mags, worked fine in the Vietnam era mag. That mag is working great now. I had less failures this time with the problematic mags in general as well.

    I put 200 rounds of steel case (I don’t usually use steel case but it’s what I had on hand at the moment) through the Rand and one of my builds with two failure to return to battery. Both failures were still with the mags I’ve got marked with nail polish on the floor plates. Mags that have been working well still are.

    I took pictures but am having issues uploading them. Flickr made me create a yahoo email apparently and I have no clue on the email.

    I am pasting a link to a photo that is identical to my malfunctions. It isn’t hanging up on the frame feed ramp.

    http://cdn0.thetruthaboutguns.com/wp...batteryjam.jpg

    On a separate note,

    Sometimes the followers get jammed in the bottom of the mag if I use a bit too much force loading the 7th round. Some of the ww2 ones do this as well. If I smack it hard against my hand the follower frees up.

  5. #15
    Join Date
    3rd February 2007
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    Make sure the steel cases have the standard sized extractor groove cut in them. If they do not, and many don’t, never use them again. Extractor abuse and damage will ensue.

    In other words if the back of the case has an extractor groove cut in in like a 30-06 or 270 case, stop using them.

  6. #16
    Join Date
    11th August 2018
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    Why would they use 30-06 extractor grooves? That doesn’t really make sense. I assume just for cost savings?

    I’ll just stick with brass for the most part. I assume aluminum is fine in ww2 1911s? I know my USP 40 is highly advised against aluminum and a few guys have had major issues with the USP line and aluminum, but when I still had glocks I usually used aluminum, and often use it in 1911s as well.

    Did the ww2 steel case 45 ball ammo have a 30-06 extractor groove? I’ve read Jeff cooper had issues with the issue 45 ammo, and lubed the cases to avoid extractor damage.

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