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Thread: difference between the bcm 16" mid lenght upper and the 16" mid lenght light weight

  1. #21
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    IMHO - In My Honest (or Humble) Opinion.

    Example of use: IMHO, we should petition Bravo Company to change the description of their 'LIGHT WEIGHT' barrels and upper receiver groups to 'Standard LIGHT WEIGHT.' (Nyuk, nyuk! :winksmiley
    Last edited by hikeeba; 05-13-11 at 09:21. Reason: Example
    One doesn't need to be sick to get better.

  2. #22
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    Quote Originally Posted by NC_DAVE View Post
    than is one really better than other. Or is it just marginal weight differnce?
    If you notice the weight is at the end of the barrel. This matters in that weight further away from the support has a greater effect. Pick up a shovel in the middle of the handle and you can carry it for days and easily raise the blade. Lift it by the end of the handle, opposite the blade, and you will fatigue quickly and have more difficulty lifting the blade.

    Same thing here. Weight saved at the muzzle end of the barrel is more noticeable than weight saved at the balance point. Years ago I learned a direct effect of this kind of weight savings with shotguns. With a +2 extension I found the muzzle-end of the gun too heavy and found that I would swing past my targets. With a +1 just having one less shell (and the associated tube length/weight) at the muzzle end meant the gun was far more "driveable" to me and I could swing from target to target without over-swinging.

    With the AR, you have not only the reduced muzzle weight to give you more control, but after a day full of shooting spent going from low-ready to engaging a target you'll also notice a difference, just like trying to lift that shovel from the handle end.

    For what most people do with their ARs (internet picture-posting and shooting from a bench) the weight savings matters not a whit. However if that were my end use I'd be looking at one of BCM's stainless-barrel uppers to begin with.

  3. #23
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    I have shot two identical guns side by side where one had the BCM 16" LW and the other had the BCM 16" standard. While the difference in how the guns drove from target to target was barely noticeable if at all, my support arm definitely fatigued faster with the standard weight. Considering the lack of a down side in standard vs. LW barrels for semi-auto applications, go for the LW.
    Last edited by calvin118; 05-13-11 at 17:11.

  4. #24
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    All I know is that the M16A1 (which is supposed to have had the same barrel profile that is now being called lightweight) was very handy and quick (even with a 20" barrel). The AR15s that I have handled with medium and Gov't and M4 profile and heaven forbid HBAR, not so much.

  5. #25
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    Hmm, I just ordered a BCM 14.5" standard upper yesterday evening.. after reading this Im thinking I might have wanted the LW version.. ??

    what about accuracy between the two? Not noticeable?? Heats up faster, giving more flyers??

  6. #26
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    Quote Originally Posted by Dirknar View Post
    Hmm, I just ordered a BCM 14.5" standard upper yesterday evening.. after reading this Im thinking I might have wanted the LW version.. ??

    what about accuracy between the two? Not noticeable?? Heats up faster, giving more flyers??
    For the average shooter, one will not see the difference in accuracy between a govt profile and a LW profile barrel now or in May 2011.

  7. #27
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    Quote Originally Posted by rob_s View Post
    If you notice the weight is at the end of the barrel. This matters in that weight further away from the support has a greater effect. Pick up a shovel in the middle of the handle and you can carry it for days and easily raise the blade. Lift it by the end of the handle, opposite the blade, and you will fatigue quickly and have more difficulty lifting the blade.

    Same thing here. Weight saved at the muzzle end of the barrel is more noticeable than weight saved at the balance point.
    Love the shovel analogy.

    While not BCM products, the leveraged weight of different Colt barrel profiles is considerable when in use.

    I started out with M4 barrel profile like the Colt 6920 (6.9lbs+8oz. railed forearm). To shave weight and speed up handling, I tried the monolithic rail 6940 (6.8lbs), which weighed around a half-pound less. The 6940 hardly handles differently, because the weight savings is further back toward the center balance point of the rifle and the barrel profile is still the M4 style. The difference in the weight dispersal is observed when you attempt to the balance the uppers but seems to be much less pronounced when using the complete rifle.

    The light-weight profile 6720 (6.2lbs) is a world of difference due to considerably less mass on the end of the barrel. The 6720 profile handles with less muscling and more fluidity, with less momentum while swinging. Light weight profiles are a force mutiplier.

  8. #28
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    ok, I just want to make sure I'm clear on this. The government and LW profiles have the same profile before the gas block correct? Or is the LW thinner than the government underneath the handguards?

    I was always under the assumption the diameter was the same under the gas tube.
    Last edited by MegademiC; 10-22-12 at 12:34.

  9. #29
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    Quote Originally Posted by ForTehNguyen View Post
    it will also cool down faster. For semi work, no performance differences. The weight difference is noticeable
    This is incorrect: a lighter (smaller diameter) barrel will never cool down faster. Given the same amount of heat input (rounds fired), a heavier profile barrel will always cool down faster.

  10. #30
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    Quote Originally Posted by usdmsw21 View Post
    This is incorrect: a lighter (smaller diameter) barrel will never cool down faster. Given the same amount of heat input (rounds fired), a heavier profile barrel will always cool down faster.
    Check the wiki on thermal mass and specific heat. Assuming the same material used (4150 CMV) then the narrower barrel will reach a higher temperature, but still cool down faster when immersed in any fluid (air).


    The profiles between LW and Gov are identical out to the journal that the gas block or FSB is mounted too. From there forward is the difference, where the LW gets machined to a smaller OD for the next 5.7" or so.
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