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Old February 24, 2018, 05:25 AM   #1
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Lightweight BCG's in an AR / M4 ???

The last time I was messing around with the AR / M4 platform, designs were moving from the carbine-length to mid-length gas systems in order to tap into lower pressures and attain a smoother recoil cycle. Many shooters were also increasing the weight of the buffer from: H, to H2, to H3, for basically the same reason: a smoother recoil cycle. Back then, all of the operating principles made perfect sense.

Now, that I've finally decided to build my own M4 carbine from parts & components, I've discovered that the latest trend is to use a lightweight / low-mass / skeletonized BCG, in order to "reduce recoil". Now, I generally like a lighter weight carbine and that is one of the primary design goals of my build. But, Whiskey Tango Foxtrot, over ???

Do these lightweight BCG's still use a heavyweight buffer and mid-length gas system? Or have new laws of physics been passed while I wasn't paying attention?

Thanx, Dave.
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Old February 24, 2018, 08:01 AM   #2
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I wouldn't recommend a lightened BCG for general use. Do you really need to "reduce recoil"? The only place this is really needed is for those "battle rattle" games where "double taps" @ 20' are the norm. Those guys can afford to beat their rifle to pieces frequently(sort of like a dragster destroying it's motor in one 1/4 mile run).
I have a light weight BCG and it has ONE purpose: to function with a specific ammo in an AR built to function in a narrow niche of performance.
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Old February 24, 2018, 10:26 AM   #3
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Less mass, less felt recoil, quicker recovery time. Generally, not needed. I've never experienced or observed such a narrow niche AR function as to require a light weight bcg. Whatcha got going Mobuck? Using an agb in conjunction with it? 3-gun? Load? Thanks.
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Old February 24, 2018, 10:32 AM   #4
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+1. I wouldn't go with a light bcg either. My thought on it is-- regardless of the gas or pistol system, there is a short time period when the case obturates and kinda needs to stay put until all the gasses get mustered up. I feel the weight of the bcg needs to retard any rearward movement until the gas or pistol begins to employ it's forces in a manner conducive to the way the system was designed. If a lighter bcg is used, then too sudden of an acceleration would just be cause for undue premature wear. Not all brass obturates the same, and keeping the bcg at it's preferred "speed limit" would reduce battering. But again, that's just my thoughts- wish I was better at explaining my thoughts.
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Old February 24, 2018, 12:02 PM   #5
Bartholomew Roberts
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Lighter buffer and BCG means less reciprocating mass to disturb sight picture for follow up shots (also less mass to push the next round into battery).

Heavier buffer and BCG delays the time it takes to unlock and cycle by milliseconds, spreading the recoil impulse out over a longer time.

Just depends on what you are trying to achieve in the overall system. A lightweight BCG and buffer is not great for an SBR with gas port erosion on a heavy firing schedule. On an 18" rifle-length gas competition gun, it may be amazing.
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Old February 24, 2018, 04:10 PM   #6
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"Whatcha got going Mobuck?"

The fallout of a carbine gassed 300AAC set up primarily for super sonic suppressed operation and making it run with lower power ammo w/o the muffler. Easier to swap BCG than to muck up the gas block settings(at least from my perspective anyway).
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Old February 24, 2018, 05:34 PM   #7
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Using an adjustable gas block, and low power spring, in combination with a light weight BCG...

You can tune it to be very mild shooting.

Great for competition and for fun... Not something I would use on any serious use rifle.
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Old February 25, 2018, 08:21 AM   #8
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+1 marine6680
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Old February 25, 2018, 08:42 AM   #9
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Originally Posted by Bartholomew Roberts
Heavier buffer and BCG delays the time it takes to unlock and cycle by milliseconds, spreading the recoil impulse out over a longer time.
This is what I do.

I have a 20 inch rifle with pencil barrel, carbon fiber handguard, and very light stock, but I use a rifle buffer with six steel and one tungsten weight. The bolt still holds open at the end of a magazine unless I am using Wolf steel cased.

The recoil is extra-ordinarily mild.

For the carbine version of that rifle, I use an H3 buffer. If I built it again I would just use a cheap solid 9mm steel buffer. It isn't as gentle as the rifle, but even Wolf steel works in it and it's very comfortable.
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