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Thread: How reliable are Low Mass BCGs

  1. #31
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    Quote Originally Posted by MistWolf View Post
    To make a gas driven rifle work properly, there are three things that need to be balanced out-
    -Mass of the reciprocating parts
    -Control of the gas flow including mass, velocity and pressure
    -Spring compression rate and rate of relaxation

    Change any one of these and the others will need to be adjusted to match.

    Let's clear up a few misconceptions. First, the only reason a change in the mass of the reciprocating parts will change how much free recoil the firearm generates is because it changes the mass of the whole firearm, not because the mass of the reciprocating parts was changed.

    Firing the same ammo at the same velocity, a firearm with greater mass has less free recoil than one with less mass. It doesn't matter where that mass is. If you were to lighten the carrier by 4 oz but added 4 oz to the barrel, the rifle will still generate the same free recoil because it still weighs the same. If you just add 4 oz to the barrel, the rifle has more mass and thus less free recoil. Will that recoil feel the same as would if those 4 ozs were added to the carrier instead? Probably not because a heavier carrier moving back and forth in the upper will feel differently than a lighter one.

    badazz posted inaccurate information about springs. Will a spring relax faster when pushing less mass than it would pushing more mass? Definitely maybe. A spring pushing a good amount of mass will relax at a slower rate, but even when pushing no mass, it has a finite rate at which it relaxes. The more you lighten the load on the spring, the less gain in velocity. It's the law of diminishing returns.

    In an AR, the spring pushes the BCG back into battery with energy that has been stored into it from the momentum of the BCG opening. The gas gets everything moving but after a short distance the gas is cut off and from there, the whole shebang is just coasting. Less mass in the BCG/buffer, the less momentum it has to compress the spring, the less momentum it has to compress the spring, the less energy the spring has stored. It's possible that the spring will not have enough speed or stored energy for reliable function.

    A heavier reciprocating mass does not mean the rifle will have softer recoil. In fact, the greater the reciprocating mass, the more likely it will cause the muzzle to move off target while in motion. If the BCG/buffer were to account for 20% of the whole mass of the rifle, it will move the rifle around more than if it were only 10%. The trade off is that the lighter BCG/buffer has to move faster to load the rifle with the same energy- or use a stiffer spring. Note that a stiffer spring isn't always a faster spring.

    A lighter BCG/buffer isn't more likely to bounce than a heavier one. There's more to it than velocity. What causes bounce is the carrier hitting the barrel extension in such a way that energy is reflection cause the two parts to bounce away from each other, like striking a hardened steel surface with a steel hammer. There's bounce. But strike that same hardened surface with a deadblow hammer designed to spread out the energy, it won't bounce at all, even if the deadblow weighed the same and strikes with the same velocity.

    The JP low mass carrier can be made to run with the same reliability as a standard full auto carrier but the rest of the system has to be tuned to make it happen. 3 gun guys don't tune their rifles that way. They tune their rifles to run at the very edge of reliability with a certain ammo for the softest recoil and least movement of the muzzle from target. When everything is in balance, a "race gun" will work every time. But that balance is delicate and easily upset.

    Bottom line is the rifle gas system with a 20 inch barrel, rifle spring and rifle buffer or A5 buffer is the most reliable and forgiving set up for an AR firing the 5.56x45. Everything else trades reliability for some other advantage such as a shorter package
    Very well said. Which is why I would only use a Lo Mos BCG along with a Syrac Adjustable gas block.
    Last edited by ryu_sekai; 08-30-13 at 21:30.

  2. #32
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    I'm not crazy about 'adjustable anything' (sights excepted) on a gun I'll trust to save my derriere; screws come loose or out of adjustment.
    Moon

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    Lo mass carriers are used for three gun shooters. They are used with large compensators, low weight buffers and adjustable gas blocks. These components are all tuned to reduce muzzle travel for multiple shots on a single target.

    Most competitiors have defense guns and competition guns. Defense guns don't run well in competitions and competition guns are not good for defensive situation (except for their accuracy!). You can own a good defensive gun for around $1000. Competition rifles start at about $2500 unless you build it yourself.

  4. #34
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    Quote Originally Posted by why1504 View Post
    Lo mass carriers are used for three gun shooters. They are used with large compensators, low weight buffers and adjustable gas blocks. These components are all tuned to reduce muzzle travel for multiple shots on a single target.

    Most competitiors have defense guns and competition guns. Defense guns don't run well in competitions and competition guns are not good for defensive situation (except for their accuracy!). You can own a good defensive gun for around $1000. Competition rifles start at about $2500 unless you build it yourself.
    I think most people forget that reliability is one of the most important things when building a 3 gun rifle.

  5. #35
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    Quote Originally Posted by halfmoonclip View Post
    I'm not crazy about 'adjustable anything' (sights excepted) on a gun I'll trust to save my derriere; screws come loose or out of adjustment.
    Moon
    If the screws come loose or fall out the syrac will work like a reg gas block.

  6. #36
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    Quote Originally Posted by ryu_sekai View Post
    I think most people forget that reliability is one of the most important things when building a 3 gun rifle.
    Same thing for the handguns, but I don't think anyone would say that a STI2011 tuned up is as reliable as a Glock or M&P. I think the key is the definition of reliable. Reliable has to be tied to what kind of maintenance cycle you're talking about- and what component fails. I have a buddy who won't clean his 2011 for thousands of rounds until it slows down- but he cleans his mags instantly if they hit the dirt. 2011s guns are reliable, the mags suck.

    I have a JP upper all tuned up. Comp, adj gas, LMOS all with a cryo'd JP SS barrel. Frankly I think it is hard to beat for ease of shooting and staying flat and accuracate. So fun to shot sub MOA targets at 400 yards and watch the splash on steel easily. Simply phenomenal. That said, the comment about the gun 'wiping' the moving parts clean is technically true- but after 400-500 rounds the gun starts to get persnickety. Less than a perfect shoulder mount and you run the risk of short stroking. The gun starts to tell you with things like not locking back on empty mags- so you get some warning signs before you get a true failure.


    The light action guns are very reliable as long as your maintenance cycle is in sync with the guns properties.
    Last edited by FromMyColdDeadHand; 08-30-13 at 23:49.
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  7. #37
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    Quote Originally Posted by ryu_sekai View Post
    I think most people forget that reliability is one of the most important things when building a 3 gun rifle.
    Except that reliability is only applicable under a specific set of conditions on the competition range. You will have time to tune your gun specifically for the load that you will be shooting as well.

    Very different from the "combat reliability" we are talking about in a fighting rifle.

  8. #38
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    Quote Originally Posted by ryu_sekai View Post
    I think most people forget that reliability is one of the most important things when building a 3 gun rifle.
    Glad you brought this up. The tactical crowd seems to think gamers are somehow OK with something that is less then reliable, which is hilarious considering how many rounds a competitive 3 gunners burns compared to durrfensive shooters. Who here spends money on planes tix, rentals and lodging for training with gear that "dosent work"? These guys are doing the same, to make a living, and have match/national titles($$$$$$) on the line. What do you lose at a training course? 10mins off the line to get a new XXXXXX or use the loaner rifle.

  9. #39
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    Quote Originally Posted by vicious_cb View Post
    Except that reliability is only applicable under a specific set of conditions on the competition range. You will have time to tune your gun specifically for the load that you will be shooting as well.

    Very different from the "combat reliability" we are talking about in a fighting rifle.
    Really, there is time before the match starts where people can burn ammo and "tune" ? This conversation is silly seeing as how easy it is to buy a gas block with the wrong sizing and how many member's in spec princess guns wont even run steel case ammo.

    Also, tell me more about the grueling condition inside your house compared to
    in which your serious use, combat fighter rifle thrives in?

  10. #40
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    Quote Originally Posted by theblackknight View Post
    This conversation is silly seeing as how easy it is to buy a gas block with the wrong sizing and how many member's in spec princess guns wont even run steel case ammo.
    This is legit. I agree in that I think members who run 14.5" middies w/ an H3 buffer are basically operating in the same realm as the gamers with their finely-tuned rifles. And, sometimes, "combat" oriented guns designed with the "bleeding edge" in mind aren't initially reliable with *all* types of ammo. The original SR-15s had this problem, and people were complaining that they wouldn't reliably cycle cheap steel-cased ammo. Why people would spent $2K+ on a rifle and then feed it the cheapest ammo you can buy is beyond me, but it was a complaint.

    So, I think you make a valid point here.

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