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9/17/2020 5:59:48 PM
Posted: 1/31/2010 8:07:35 AM EDT
I see uppers described as A2, A3 and A4.  What does that mean?

Is an upper the complete barrel assembly, i.e. the upper half of a gun?  If you buy say a Bushmaster upper can you put that on a Armalite lower?
Link Posted: 1/31/2010 9:25:44 AM EDT
[Last Edit: 1/31/2010 9:26:52 AM EDT by cmcflex]
Originally Posted By klw:
I see uppers described as A2, A3 and A4.  What does that mean?

They correspond to the upper receiver.

A2 is an upper receiver with the fixed carry handle (i.e., you can't take off the carry handle––it's machined with the upper receiver) and the rear sight is adjustable for elevation and windage (A1 uppers are only adjustable for windage).

A3 is a flat-top upper receiver with a removable carry handle.

A4 is a flat-top upper receiver.


Is an upper the complete barrel assembly, i.e. the upper half of a gun?  If you buy say a Bushmaster upper can you put that on a Armalite lower?

Yes.


If I'm wrong, I'm sure someone will come along to correct me.

Edit: grammar.
Link Posted: 1/31/2010 9:25:59 AM EDT
A2 is fixed carry handle with upgraded A2 sights

A3 is a flattop

A4 is used to describe a 20" bbl with flattop upper

Upper can be used to describe a barreled upper, or just the receiver portion
Link Posted: 1/31/2010 4:33:38 PM EDT
Thank you.
Link Posted: 1/31/2010 6:14:10 PM EDT
Most are:

A2 - Fixed carry handle

A3 - Flat Top

A4 - Flat top with removable carry handle
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