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Discussion Starter #1
Just curious... is the Colt LE6940 lower compatible with other manufacturers complete uppers? I am reading comments here and there about "proprietary" aspects of the Colts so I am interested in how this impacts using uppers from other makers.
 

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Daggone......I was just thinking about this...
What about bolt carrier groups? Are they interchangeable across the majority of ARs? Lets say Armalite into a Colt, Busmaster, DD?

I know my Armalite bolt face is different from other bolt faces in that it has an asymetical lug pattern to reduce rotational torque. However, that wouldn't matter in a swap.

Could I just swap out a BCG with my buddies and go on shooting?
 

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Discussion Starter #5
Daggone......I was just thinking about this...
What about bolt carrier groups? Are they interchangeable across the majority of ARs? Lets say Armalite into a Colt, Busmaster, DD?

I know my Armalite bolt face is different from other bolt faces in that it has an asymetical lug pattern to reduce rotational torque. However, that wouldn't matter in a swap.

Could I just swap out a BCG with my buddies and go on shooting?
Good question... hoping we can get a few more detailed chime ins for a complete and full understanding of the cross compatability contraints or lack there of.
 

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Unless you're talking about piston BCG's, and assuming they are all in spec, you can swap BCG's to your little heart's content.
 

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Great! That would make sense considering the large number of after market parts available and things like .22 conversion kits being standardized.

Since the AR was the first successful gun design made with numerically controlled machines in small factories by skilled machinists, anything other than standardization would have been an "odd man out" situation (Remember the Sony Beta-Max? Great performance, bad marketing.)

AR manufacturing is characterized by a large number of smaller manufacturers using CDC machines to produce high quality, high tolerance parts and guns.

It's the "unseen hand of the free market" in action.

Maybe that's why the Administration would ban them!
 

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Unless you're talking about piston BCG's, and assuming they are all in spec, you can swap BCG's to your little heart's content.
Good to know! Thanks!

Is it true that I can not upgrade the trigger on the Colt with another manufactures?
 

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Mil spec should be mil spec and parts interchangable. Besides establishing minimum quality standards for gvt. purchases, they are made so they can be interchanged within the same specification. That would definitely include any 5.56 mil spec bolt group.

Newer Colts use the small pins for the Trigger groups, no?
 

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Good to know! Thanks!

Is it true that I can not upgrade the trigger on the Colt with another manufactures?

There are aftermarket triggers for both the older Colt .170" pins and the newer ones all use the standard .154" pins that are the same as the rest.
 

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Mil spec should be mil spec and parts interchangable. Besides establishing minimum quality standards for gvt. purchases, they are made so they can be interchanged within the same specification. That would definitely include any 5.56 mil spec bolt group.

Newer Colts use the small pins for the Trigger groups, no?

Si! Es verdad!
 

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With regard to BCG interchangeability on Colts - Some older civilian model Colt ARs have a sear block in the lower that prevents you from using an M16 Bolt Carrier with those lowers. Even some "standard" AR15 Bolt carriers may not work with a Colt lower that has the sear block. The sear block Colts originally came with a special half moon bolt carrier.

The sear blocks were found mostly in older Colt sporter and competition models and not on any LE/Govt Carbines AFAIK. No modern Colt ARs, LE or civilian, have sear blocks.
 

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I think I know why, but why?

Can a new bolt be reliably used in a used carrier?
If the parts are new, you can usually use any bolt with any barrel, although I would check the headspacing unless both parts were from top manufacturers like Colt, BCM, Daniels, or LMT.

Once the parts have been used, they start wearing together. I would never shoot a used bolt or barrel with different parts without checking the headspace first.
 
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