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Thread: Buffer Spring Question?

  1. #1
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    Buffer Spring Question?

    Does anyone know if the buffer spring has a specified spring weight? Like a 15 lbs spring for example or does the TDP just go by length?
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    "Action Spring" . . . I was about to say the buffer has no spring.

    Anyway, the spring particulars are:

    At a compressed length of 6.90 inches, the spring should develop 5.96 +/-1.0 lbs

    At a compressed length of 2.98 inches, the spring should develop 12.12 +/- 1.0 lbs

    (You can calculate the spring rate from these two points.)

    I never liked terms such as " a 15 pound spring", as it doesn't tell you much, but generally is the load developed at solid height, or the maximum force it can develop. Not very useful. (This would be a 12 pound spring) To confuse things, sometimes the term is used to denote the spring rate, (in which case the action spring would be around 1.5 pounds).

    EDIT: That is for the 10.70 inch long, 38 coil, standard carbine spring.
    Last edited by lysander; 03-19-24 at 20:08.

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    deleted post (it was in error)
    Last edited by lysander; 03-19-24 at 20:09.

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    Thank you for the numbers and the explanation.
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    I was trying to do the same thing figuring out the compressed weight of the standard spring vs a flatwire spring. I wanted to get the same weight out of a cut down flatwire to reduce the closing force but still have the longer lasting of flat wire. I was using a rifle buffer extension and a fish scale to pull the spring compressed but the fish scale was not high enough and my bow scale started to high to measure.

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    Quote Originally Posted by joedirt199 View Post
    I was trying to do the same thing figuring out the compressed weight of the standard spring vs a flatwire spring. I wanted to get the same weight out of a cut down flatwire to reduce the closing force but still have the longer lasting of flat wire. I was using a rifle buffer extension and a fish scale to pull the spring compressed but the fish scale was not high enough and my bow scale started to high to measure.
    Not for nuttin... but why not just buy some extra Colt springs?
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

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    Quote Originally Posted by joedirt199 View Post
    I was trying to do the same thing figuring out the compressed weight of the standard spring vs a flatwire spring. I wanted to get the same weight out of a cut down flatwire to reduce the closing force but still have the longer lasting of flat wire. I was using a rifle buffer extension and a fish scale to pull the spring compressed but the fish scale was not high enough and my bow scale started to high to measure.
    Cutting coils off a spring increases the spring rate.

    The standard carbine spring holds the bolt close with about 6 pounds force, when the bolt is fully to the rear the spring develops about 11.5 pounds.

    If you clip off two coils, the force holding the bold closed drops to around 4 pounds, and the force with the bolt fully to the rear is about 10.2 pounds.

    Your closing force drops a bit, but the force holding the bold closed drops substantially more. It is not something I would not recommend.

    Flat wire springs have a lower spring rate than standard spring, they are just considerably longer, so the develop the same pre-load (~6 lbs). Chopping a flat wire spring off gives you the troubles of the reduced coil standard spring (low holding force), and the disadvantages of the standard length round wire spring (high spring rate). Why would you want to do that?

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    Quote Originally Posted by lysander View Post
    I use this setup and it measured exactly what you said it would in a prior post above, +/- compressed to 3". The length of the cutoff buffer tube measured internally. These pics are about 2 years old from my archives.




    Last edited by the AR-15 Junkie; 03-22-24 at 17:49.

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    A regular uncut receiver extension with buffer installed will measure the other point (6.75").

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