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Thread: Reciprocating mass and the recoil impulse

  1. #11
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    Thanks very much, guys. All very helpful (and fascinating) information.

  2. #12
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    I'd call it sticky material. It's the best explanation I've seen of a very interesting topic.
    "Men speak of natural rights, but I challenge any one to show where in nature any rights existed or were recognized until there was established for their declaration and protection a duly promulgated body of corresponding laws." --Calvin Coolidge

  3. #13
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    Quote Originally Posted by OutlawDon View Post
    I'm curious too.

    Someone needs to do some scientific testing on the same day with the same gun and switch between a heavy BCG/buffer setup vs a light BCG/buffer setup.
    You shouldn't really need to do that. This is something that can be answered definitively on a piece of paper without ever touching a firearm.

  4. #14
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    Quote Originally Posted by OutlawDon View Post
    Someone needs to do some scientific testing on the same day with the same gun and switch between a heavy BCG/buffer setup vs a light BCG/buffer setup.
    +1

    And I'd like to see it complicated further by using lighter and heavier bullets, i.e. 55gr M193 vs 75gr TAP.

    Doing calculations on paper is a good start, but IMHO real world testing is really necessary to understand how these things change "felt" recoil.

    Bimmer

  5. #15
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    So why don't you buy both carriers, load your own bullets, and do it yourself?

    Sheesh.

  6. #16
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    I don't see these as contradictory. I have not been in school for 20 years or more but the heavier buffer changes the length of time that the force of the recoil is felt over which reduces the feeling of recoil. The impulse is longer


    the lighter mass is a lighter recoil to start with though it may be moving slightly faster.

    Someone tosses a big boulder at your shoulder vs a small pebble. You feel the boulder more. But if someone hucks a small pebble at your shoulder versus pushing your shoulder slowly with a large boulder, you may feel the pebble more painfully.
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  7. #17
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    No, the principles aren't contradictory once they've been more thoroughly explained. But when people were just referring to them absent of context, it certainly seemed contradictory to me. In keeping with your analogy, I might be confused if a bunch of people said, "getting hit with pebbles hurts a lot less than getting hit with boulders," while others said the exact opposite.

    Factoring intensity over time into the equation brings the context I needed to understand why people could claim "less felt recoil" on both ends on the spectrum. I wouldn't have been confused in the beginning if people said, "I like to slow down the recoil impulse and spread it over time" or "I like to get the recoil cycle over with as quickly as possible so there is less time to disrupt my sight alignment." But the absolute statements of "heavy = less felt recoil" and "light = less felt recoil" are what made me scratch my head.

    I'm not saying the confusion is anyone's fault but my own - just explaining why I originally thought it was contradictory.

  8. #18
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    Quote Originally Posted by Byron View Post
    No, the principles aren't contradictory once they've been more thoroughly explained. But when people were just referring to them absent of context, it certainly seemed contradictory to me. In keeping with your analogy, I might be confused if a bunch of people said, "getting hit with pebbles hurts a lot less than getting hit with boulders," while others said the exact opposite.

    Factoring intensity over time into the equation brings the context I needed to understand why people could claim "less felt recoil" on both ends on the spectrum. I wouldn't have been confused in the beginning if people said, "I like to slow down the recoil impulse and spread it over time" or "I like to get the recoil cycle over with as quickly as possible so there is less time to disrupt my sight alignment." But the absolute statements of "heavy = less felt recoil" and "light = less felt recoil" are what made me scratch my head.

    I'm not saying the confusion is anyone's fault but my own - just explaining why I originally thought it was contradictory.
    There is much more to it than simply the immediate effect of greater reciprocating mass.

    There is what happens to the expanding gas, when it meets greater than normal resistance, there is the noted slower acceleration of the buffer, there is it's noted increase in inertia, there is the recoil spring's ability to convert the extra mechanical energy into heat energy, and importantly, there is the volume of space occupied within the buffer by it's weights, as well as air pressure within the receiver extension.

    The result will be quite different when these variables change even a small amount.

    What may seem obvious can be quite incorrect if the system is set up a certain way.

    Energy is used to accelerate that mass. The same energy you will find at the end, when it reaches the extent of it's travel. This is because you are acting on the increased mass with the same amount of force you used with the lower mass. It's not like hurling a brick versus a pebble, where you must hurl that brick with more force. The force remains the same. The input energy is a constant. Think of it more like using a spring loaded punch to fire a marble into another spring attached to a scale. Swap in a ball bearing, and the added mass is compensated for by a lower velocity.

    It isn't as simple as you might think... And yet it is, when you look at it properly.

    There are other factors, though, that have significant effect. This isn't all there is to it, but it's a lot of it.

  9. #19
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    Quote Originally Posted by kennith13 View Post
    It's not like hurling a brick versus a pebble, where you must hurl that brick with more force. The force remains the same. The input energy is a constant.
    Don't worry: that analogy didn't confuse me. I got what e-guns was saying regarding different expressions of energy: a slow, heavy push vs a fast, sharp blow. I understood that he meant the same input energy being expressed in different ways - the way that Robb above talked about different handgun rounds and their respective recoil profiles.

  10. #20
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    I am new to the the AR platform. So please excuse if my question has been answered.

    I have a 16" upper w midlength gas system. I built the lower. Bought the CTR w milspec buffer tube, H2 buffer, and complete upper.

    A few Q's:

    i.) What do I need to do to lessen the muzzle rise and recoil such to get back on target quicker?
    ii.) How do I id the buffer spring, as I am not sure what type it is?
    iii.) Is the H2 buffer too heavy or too light?

    thx in advance.

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