Full vs semi M4 BCG?
What is the difference between a full auto and semi auto bolt carrier group for AR-15/M-16/M-4??
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This pretty much explains it:
http://www.m4carbine.net/showthread.php?t=145340 -
I'm curious too. Because as I read that, I noticed the cutouts on the AR-15's looked like the cut-outs on the M16 and vice-versa.
I was under the understanding that the symetrical cutout in the back was an AR-15 BC and the non-symetrical (cut further back on the bottom) was the M16. Reason being is to allow the hammer more clearance during full auto operation. Whether heavy or light, the BCG speed is adjusted by the buffer spring tension.
Correct me if I'm wrong, but that is the way I thought it was.0 -
Left to right, AR15-AR15-M16.
Sandwarrier has it backwards [;)]
Colt started putting the 16 BCG in the AR as the extra weight helped the function of the gun.0 -
The original design - both full and semiauto - was the one on the right:
As the bolt carrier cycled the forward edge of it's rear portion served to trip the auto sear on their full auto rifles.
To make it more difficult to convert a semiauto rifle to full auto Colt went through several changes of the carrier's rear portion over the years, eventually reaching the point that the entire rear portion was just a semicircle.
The problem was that these modifications greatly lightened the carrier, which led to bolt inertia related functional issues.
Several years ago BATFE backed off of their restrictions against M16 carriers in semiauto rifles and now all Colt Defense rifles leave the factory with the type carrier Eugene Stoner designed the rifle to use.0 -
I had an early M-16 for a year and I never did figure out what the internal difference was when the safety lever was flipped a full 180. Now the M14- there was a trigger system I could understand. 0 -
quote:Originally posted by dcs shooters
Left to right, AR15-AR15-M16.
Sandwarrier has it backwards [;)]
Colt started putting the 16 BCG in the AR as the extra weight helped the function of the gun.
That's interesting...because the one I used to clean, when I was in the service, looked just like the one in the middle[;)]0 -
quote:Originally posted by tjbaron67
What is the difference between a full auto and semi auto bolt carrier group for AR-15/M-16/M-4??
didnt we just do this a week ago?
edit: yup. we did.
http://forums.GunBroker.com/topic.asp?TOPIC_ID=588931&SearchTerms=bolt,carrier0 -
quote:Originally posted by Ray B
I had an early M-16 for a year and I never did figure out what the internal difference was when the safety lever was flipped a full 180.Bushmaster has about the best open source animation to help understand the different operations of these rifles. Among other things, it clearly demonstrates the auto sear/bolt carrier relation I referred to.
http://www.bushmaster.com/anatomy_bushmaster.asp
Lots of good tools with this one.0
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