Can you guys tell me the difference between an A4 and A3 reciever?  Without the cary handle installed, the A4 looks similar to the A3.

Thanks

An M16A3 is the full auto version of an M16A2.  There is no A3 upper, many people call an A4 upper an A3 but they are wrong.  An A4 upper is a flat top upper without M4 cuts.

 

What are M4 cuts?

The receiver on the left is an A2/A4 upper, the one on the right is an M4 upper, notice the extended feed ramps, those are the M4 cuts.
Edited to fix spelling





ETA:  Above is based on military standards.  Many manufacturers may make uppers that they call A3 and A4.  You will have to ask the specific manufacturer about their uppers.

 





 

Thanks.  That is really helpful.

You're welcome, glad that I could help.



 

if A4 is a flat top without M4 cuts. would it still be called an A4 if it did have the M4 cuts? or is that what people call an A3?

If the flat top has M4 cuts then it's a M4 upper.  Most places sells the uppers as "flat tops" and most of the time they have M4 cuts.  There are still some hold outs that sell them minus the m4 cuts but it's more common these days to have them than not.

"A3" is an old misnomer.  

When Colt originally developed the flattop upper and the M16A2E4 was being tested, they assumed that it would eventually be designated the "M16A3."  

They were incorrect, as the M16A2E3 became type classified as the M16A3 - which was a stock M16A2 except with a full auto fire control group instead of a burst group.  Unfortunately, some magazines, SOF in particular had showed the new flattop model and called it the "M16A3" creating the association with the "A3" and flattop upper receiver.

The flattop version of the M16A2, the M16A2E4 was type classified M16A4.  

Thus, an A4 upper receiver is one that is correct for an M16A4 - flattop without extended carbine feedramp cuts in the upper receiver.  An M4 upper receiver is one that would belong on an M4 Carbine - i.e. with extended carbine feedramps.  The A3 upper continues to be the M16A2 upper - no feedramps, fixed carry handle with elevation adjustments.  

There is some evidence that M16A3s are being retrofitted in the service with M16A4 (flattop) upper receivers, and that some Sabre Defence M16A3s were issued with A4 uppers, however, they are just that - M16A3s with A4 uppers.    

~Augee

can't answer a question any better then that,,,  thanks