Can anyone identify & date this BCG? Thanks

[Rex762]

 

[Spas-12 Owner]

Colt half circle BCG. Used in Sear block Colt's of the late 80's and 90's.

 

[Rex762]

Thank you for this! In theory, they should all function the same?

 

[Spas-12 Owner]

Thank you for this! In theory, they should all function the same?

The half circle BCG are the only ones that work in a sear blocked AR.

The M16 BCG are heavier and tend to work better on a over gas gun or just in general as most manufacturers today use a M16 BCG.

I only see AR-15 bolts on older (pre 2005 ish, after Colt ATF letter ) .

The legality of an M16 part in your AR- the short version. > Legal Section > AR15.COM

In order to condense the infamous thread, still tacked, regarding this issue down to the bare bones of the law and letters, I have created this post. Before you read this, please understand that I, a

www.ar15.com

Problems have been linked for years to the lessened weight of the semi auto bolt carrier and the shape of the rear most portion of all 4 types of semi-auto carriers that have been designed over the years. Tests even proved that although one might not realize it, the rear of the bolt carrier in the half-circle design, actually flexes and vibrates during firing. This, along with the carriers weighing less than was intended in original design has been found to be responsible for a lot of malfuctions and excessive parts wear due to the bolt carrier actually sliding and grinding against the upper receiver and receiver extension when the flexing and vibration occurs.

 

[Rex762]

Thanks for the information. My lower does not have sear block Thinking about using a different BCG, good idea?

 

[Spas-12 Owner]

Thanks for the information. My lower does not have sear block Thinking about using a different BCG, good idea?

I would use a different BCG personally, but if it works for you, run it!