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Old 09-28-2012, 05:22 AM   #1
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Default Dwell time.

I want to buy a full auto BCG for my LMT CQB MRP. The BCM one looks good except the logo in there (if it really is on the item and not just in the ad photo?) detracts a bit from my gun being all original.

LMT is unfortunately out of stock. I want a whole ass'y so I have the original semi auto BCG as a spare.

Here's the thing though. In the blurb about it it says it.... Our enhanced carriers incorporate a longer dwell time allowing barrel pressure to be greatly reduced and promoting easier extraction

My question is, does this mean the weapon with a full auto BCG will not be able to fire "as fast as you can pull the trigger" ......as fast as a semi-auto BCG will allow the weapon to fire..."as fast as you can pull the trigger?"

I am assuming dwell time is the time it takes the bolt to cycle....to extract and load a new round?

In other words....a semi auto BCG in a full auto M4 would then, in return, give a faster cyclic rate at full auto.....no? Can you even fit one to a full auto weapon?

But going back to the full auto on a semi auto CA compliant weapon...... would this be noticeable doing double taps, or such an infinitesimal difference as to not be an issue even in the slightest? I can't imagine it would, but I am just curious.

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Old 09-28-2012, 05:31 AM   #2
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Originally Posted by Fumbles View Post
I want to buy a full auto BCG for my LMT CQB MRP. The BCM one looks good except the logo in there (if it really is on the item and not just in the ad photo?) detracts a bit from my gun being all original.

LMT is unfortunately out of stock. I want a whole ass'y so I have the original semi auto BCG as a spare.

Here's the thing though. In the blurb about it it says it.... Our enhanced carriers incorporate a longer dwell time allowing barrel pressure to be greatly reduced and promoting easier extraction

My question is, does this mean the weapon with a full auto BCG will not be able to fire "as fast as you can pull the trigger" ......as fast as a semi-auto BCG will allow the weapon to fire..."as fast as you can pull the trigger?"

I am assuming dwell time is the time it takes the bolt to cycle....to extract and load a new round?

In other words....a semi auto BCG in a full auto M4 would then, in return, give a faster cyclic rate at full auto.....no? Can you even fit one to a full auto weapon?

But going back to the full auto on a semi auto CA compliant weapon...... would this be noticeable doing double taps, or such an infinitesimal difference as to not be an issue even in the slightest? I can't imagine it would, but I am just curious.
unless you can pull the trigger substantially faster than about 10.5 times per second (approx cyclic rate of a full auto M16) you wont notice a difference. semi auto guns run better and smoother and more reliably with a full auto carrier. mainly due to the extra mass increasing dwell time and allowing the case to chrink back to more normal dimensions. this allows the bolt to extract the case easier than having to forcefully yank it under pressure and still sticking to the chamber walls.

the bcm bcg is about as good as it gets for a great carrier group. they all have the bcm logo but thats not a bad thing. makes it easier to sell if you ever decide to.
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Old 09-28-2012, 06:54 AM   #3
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The bullet exits the barrel waaaay faster than you can get off a second shot. Dwell time is measured in limi seconds and will not affect how fast you will be able to shoot with a semi auto fire control group. As JonM has mentioned its not anything you should worry about.

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Old 09-28-2012, 06:57 AM   #4
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Thanks. Yeah I see the BCM get's high points, interesting that they themselves speak extremely highly about the LMT full auto BCG and LMT in general.

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Old 09-28-2012, 12:13 PM   #5
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Thanks. Yeah I see the BCM get's high points, interesting that they themselves speak extremely highly about the LMT full auto BCG and LMT in general.
Thats because bravo company is a class act and give credit to good products
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Old 09-28-2012, 02:08 PM   #6
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Thats because bravo company is a class act and give credit to good products
While that may also be true one must not overlook the fact that BCM did, and may still be, purchase several parts from LMT which they used in their rifles. The companies have a history that dates back to when BCM was first started, around 2003.

LMT was founded back in the 80's and was a recognized source for quality components.

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Old 09-28-2012, 02:47 PM   #7
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Dwell time is the time that gas is being vented from the gas port until the bullet exits the muzzle.

The FA carrier really increases the inertia of the bolt so unlocking happens later in the dwell time. Lots of guys who run FA rifles like a heavier carrier and buffer to slow the cyclic rate to make it more controllable. On carbines it improves extraction and decreases stresses in the extractor parts.

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