A2, A3, A4, M4????

I feel like a real novice not knowing this, but could someone please tell me the difference between the various rifle designations, A2, A3, A4, and M4? As always, any insight you guys can offer me is greatly appreciated.

Captain,
Great question. Having a pretty good idea, but not knowing the specifics, I did some fascinating web research. This is what I came up with. The fully automatic M16 was the initial version first adopted in 1964 by the USAF. This version did not have a forward assist and no elevation adjustment of the rear sight. It is the version that utilized a triangular forearm. The U.S. Army began to distribute this rifle to it’s forces in Vietnam early 1965. The US Marine Corps adopted the rifle also. It was standardized as the M16A1 in 1967 with a few modifications. First, and in my opinion the most important, it was issued with a fricken cleaning kit. The second, A1 incorporated the forward assist. This version remained the primary infantry rifle of the US military from 1967 until the 1980s. Then it was supplemented by the M16A2. This version had improved adjusable elevation sight system and three round burst capability. During the early 1980s a standardized cartridge was adopted. The 5.56 mm NATO. The M16A3 again had a fully-automatic capability and a flat top without a carry handle, issued primarily within the United States Navy. The M16A2, in turn, is currently being supplemented by the M16A4, which also had the flattop receiver and this was the platform eventually developed into the M4 Carbine with the Picatinny rail System.

The A1, A2, A3, and A4 all stand for the generational configurations of the M16 Rifle. A simplistic description of each version:
-A1 Upper has the non removable carry handle and rear sight. Short butt stock
-A2 Upper also has the non removable carry handle but the rear sight has an added elevation adjustment knob. Longer butt stock and a four position telescopic or collapsible stock.
-A3 Upper is the Flat top uppers
-M4 with a flattop upper, carbine gas system, fatter hand guard and variations included additional weapon systems such as a grenade launcher and shotgun attachments. I ask to be corrected if I have made a mistake, however this is my understanding of this firearm and it’s variations.

"When you're determined to survive, you leave nothing to chance."

That's excellent info guys. I recently bought a Rock River LAR-15 in 5.56 off a buddy of mine (at a great price,) and wasn't sure which one it was. Mine has a fixed carry handle, adjustable rear stock, and fully adjustable rear site, so I'm assuming it's an A2.

Captain Brad,
That would be my assumption. Congratulations on your latest acquisition.
I'm glad it went to a good home.

"When you're determined to survive, you leave nothing to chance."

Thanks Chain and Fred...I don't think I'll be getting rid of mine any time soon. Do either of you know what the L in LAR-15 stands for?
I'm definitely not worried about getting my money out of it. It came with a scope, case, 2-40 round and 2-30 round mags, and 700 rounds of ammo. I gave 900 for it.

Right place right time.

actually Smith the M16 is part of the AR15 design just a new word the Marine Corp renamed and change some things in the late 1970's.

A good man does nothing in battle of the enemy. so create sin and be ready for the next attack.

So, would I consider mine as a AR15,A3 if I were trying to help identify the design of my rifle to someone?