Re: AR 15 A4 vs AR 15 A3 UPPERS
Ok, well... where to start.
First off, a bit of .mil info:
The M16A1 had a simple rear sight called "field sights". The M16A2 had adjustable target like rear sight(among other improvements and changes). The M16A2 was also 3 round burst instead of full auto. Some parts of the military,(more specifically the Navy, wanted a full auto M16A2) so the M16A3 was made. The M16A3 being a full auto A2. Later the M16A4 was adopted, which is an A2 with a flat top railed upper.
Now on to commercial sales. Civilian manufactures made A1 and A2 uppers. When the flat tops came out, instead of calling them A4 uppers, many dealers and manufactures called them A3 uppers.
Now it gets more complicated. The .mil decided on steeper feedramps on the M4 to help feeding with old worn out mags. These steeper feedramps require a deeper cut in the barrel extension and the upper. These are often called "M4 Feedramps"
A barrel with M4 feedramps will work fine in a upper w/o M4 feedramps. However an M4 feedramp cut upper may have issues with a barrel w/o M4 feedramps.
Recall that civilian manufactures were calling their flat top uppers A3 uppers. Now some of these companies as they started offering flat top uppers with M4 feedramps started to call these others uppers A4 uppers.
Awesome naming conventions right?
So whats the difference between an A3 and an A4 upper?
Well that depends on the company and what they mean when that individual company names their product.
And yes, after all that I still haven't answered your question. HA!