What is the diffrence between an A3 and A4 upper? Thanks

My AR is an A3 (flattop), and my Hk/FMP is an A4 (folding stock).

Not quite sure what an A4 AR is.

A3 = full auto M16A2
A4 = flat-top M16A2

Just as Mav says.

The M16A2 and M16A3 are identical other than the A2 having BURST and the A3 having AUTO on the selector.  Fixed handles.  No difference whatsoever in the upper, just the lower.

The M16A4 has a detachable handle and the same BURST onthe selector as the A2.

There's only the M4 and M4A1.  Both have detachable handles (other than a few very early M4s) with BURST and AUTO respectively.

Civilian ar15 "nomenclature" is totally inconsistent across brands and not indicative of the rifle's or carbine's configuration.  If you want a flattop receiver specify flattop, not an A-number.

-- Chuck

In terms of the civilion AR-15 not military weapons the A3 and A4 are exactaly the same. Like how bushmaster and DPMS call their flat top an A3 and Rock River arms calls it an A4 but it is all the same upper.

[url=groups.msn.com/TheMarylandAR15ShootersSite/whatisana1a2a3ora4.msnw]What is an A1, A2, A3, or A4?[/url]