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Thread: BCM 14.5 Mid Length T&E/Range Report

  1. #161
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    Quote Originally Posted by markm View Post
    The H3 buffer is crazy. Like I wrote back on page 1 or whatever.... H3 plus hornady steel cased feels like a rimfire conversion.

    I'm still sticking with the H2 to give a margin for error.
    I guess that's my main question as well. For those of us w/ BCM 16" middy's, can we run an H3 also? I know an H2 will work (it's what I use currently)...but I'm envious of what you're getting with the H3. The guns hots like a damn ray-gun...it just doesn't hardly move!

    I'd think that, if the gas ports were the same, the 16" should run an H3 as well, since it has more dwell time.

    What say you, Mark?

  2. #162
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    What I don't get is how a heavier buffer actually feels softer, you would think that a heavier mass would have more inertia and actually have more recoil, this is why the 3-gunners run light weight carriers and carbine buffers....

    I guess the heavier buffer slows down the BCG so it never gets up to the speed of a BCG with a carbine buffer and the balance of speed vs mass for the mid-length gas system means longer dwell time so smaller port size required to run the action, slow it down with a heavier buffer even more....

    Weird, less mass in the moving parts means less felt recoil, yet we add a heavier buffer (more mass) and the rifle recoils less....

    Cameron

  3. #163
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    Quote Originally Posted by Cameron View Post
    What I don't get is how a heavier buffer actually feels softer, you would think that a heavier mass would have more inertia and actually have more recoil, this is why the 3-gunners run light weight carriers and carbine buffers....

    I guess the heavier buffer slows down the BCG so it never gets up to the speed of a BCG with a carbine buffer and the balance of speed vs mass for the mid-length gas system means longer dwell time so smaller port size required to run the action, slow it down with a heavier buffer even more....

    Weird, less mass in the moving parts means less felt recoil, yet we add a heavier buffer (more mass) and the rifle recoils less....

    Cameron
    Cam,

    I was thinking about this exact thing last night. I think it all comes down to reducing the speed and force of the impact of the buffer/BCG on the rear of the receiver extension during recoil. I think that the lighter BCG/buffer setups (like JP's) have so little mass, that the buffer spring begins to arrest the BCG and substantially slow it before it impacts the receiver extension (like it's running out on springs). I'm thinking that the heavier setups like we're using take advantage of the added mass to counteract the gas delivered to the system, and also reduce the speed with which the BCG impacts the rear of the RE tube. This is all conjecture at this point, since I do not own a lightweight setup.

    However, a background in speaker design gives me a little insight. Subwoofer drivers fall into two categories: Heavy-coned mass controlled rivers, and lightweight-coned 'SPL' drivers (heat controlled). The heavy coned drivers use increased cone mass to regulate the limits of their excursion.....but the SPL drivers use a stronger magnet and more voice-coil windings to establish more control over the lighter driver.

    it seems this would be analogous to the heavy BCG-buffer, light spring/ light BCG-buffer, heavy spring debate. Maybe. And maybe I'm just talkin' out of my a$$.

    I'm trying to wrap my noodle around this stuff.

    Any experts out there? GotM4...Rob_s.....KevinB.....Iraqgunz......ANYBODY?

    If 87 is listening, this might be a good idea for another vi.....
    Last edited by BufordTJustice; 08-15-10 at 16:42.

  4. #164
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    It's basic inertia - you have a set amount of gas (force) coming into the system based up on your setup (carbine, middy, rifle, etc.). The gas exerts it's force onto the BCG and transfers into the buffer. Since an object that is at rest will stay at rest unless an unbalanced force acts upon it, this force moves both the BCG and the buffer only once it has overcome the system's inertia.

    The more mass, the more force that is exerted to overcome inertia. Since the amount of force available is finite and already determined you should have the following outcomes: If you have a light buffer, less force is exerted overcoming inertia and more force is put into the actual movement of the BCG and buffer. If you have a heavier buffer, more force is used to overcome inertia and not as much is available to move the BCG and buffer - thus slower movement with less impact on the rear of the receiver extension. All of this assumes that the spring is the same. If you change the resistance of the spring, you are simply changing that part of the equation - however if you test a light buffer and heavy buffer with each spring setup, you should notice that the same holds true in either case.

    This is why you have the potential to run into reliability problems with heavier buffers... if you slow the system down too much you can cause it to not function as intended...
    Last edited by CaptainDooley; 08-15-10 at 23:44.
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  5. #165
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    Any know what the gas port size is?

    Are they "larger" or "smaller"?

    Tried several searches with no real answer. Trying to find out their recipe.

  6. #166
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    Quote Originally Posted by BufordTJustice View Post
    I'd think that, if the gas ports were the same, the 16" should run an H3 as well, since it has more dwell time.

    What say you, Mark?
    I would guess that the gas ports are the same. There's a guy in Cameron's thread who has been running an H3 in his 16" for a long time with no problems.

    Quote Originally Posted by Cameron View Post
    Weird, less mass in the moving parts means less felt recoil, yet we add a heavier buffer (more mass) and the rifle recoils less....
    Yep. Running the H3 with mild ammo is like having someone manually cycle the action where there's no rearward slam of the buffer.
    Last edited by markm; 08-16-10 at 18:55.

  7. #167
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    I asked about the heavier/lighter buffer and got a lot of great responses in this thread:

    Reciprocating mass and the recoil impulse

  8. #168
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    video of me shooting at CFDCC yeterday

    Three and four round "bursts" are very easy with this gun. I was able to put 3-4 rounds per target in the time most other shooters were putting 2 rounds per target.

  9. #169
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    Rob... I had no idea you were in Florida. I missed the shoot yesterday. Now I really hate that I missed it. Good to see another M4Cer

  10. #170
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    Quote Originally Posted by toekneeg View Post
    Rob... I had no idea you were in Florida. I missed the shoot yesterday. Now I really hate that I missed it. Good to see another M4Cer
    Yup, 3 hours each way.

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