Ok, I am pretty retarded when it comes to ARs, I know just enough to get me in trouble and that's about it.  I bought a new Bushmaster probably going on 5 years ago.  I have put maybe...at most... pushing it... 1000 rounds through it.  Well I recently dug it out, blew off the dust and ordered a Leo Mark AR scope for it.  So it kinda got the bug going again so I decided to come check out the site.  I have bee lurking for a couple of weeks now (posting here and there in the scope forum) .  Anyway,  holy cow why is there so many manufacturers now?  Seems like everybody and their neighbor is either making full AR15s or parts for them.  I am so confused who is good, who is crap and so on and so forth.  I thought when I bought my Bushmaster they were right there at the top of the quality and demand list, now it seems like they are kinda low on the list.  And who the heck is manufacturing the M16 for our boys now.  I always thought it was Colt, but now It seems like there are all kinds manufacturing for the government, or maybe colt hasn't done it in a long time.  It also seems like when ever I see pictures of our Military boys with their M16, they always seem to have some sweet scope, or sight, or some other sweet set up.  ( im not complaining, i think it is awesome, what ever it takes to save our guys and put a bullet where it is supposed to go.)  So how does that work, do our men get issued a gun and then they can customize it to however they want, or do they get stuck with what they get handed.  I am just curious how that whole system works.  Do they keep the same gun the whole time they are in the military? Can they take any kind of souvenir with them when they go home.  Like a scope mount or hand guard or anything that was kinda their signature to their gun?  I am just curious and am sick of keeping my wife up tonight from not being able to sleep.

I'm not military, so I'll leave those questions to those more qualified than me.  However, I understand FN is now making the M16.  Colt is still making the M4 though.

BM is still GTG but smaller companies like BCM, Daniel Defense and Spikes have raised the bar of expectations, quality control and thus quality.

You might skip a line between your questions so people can answer them more conscisely.

currently most M16's are FN and for the time being all M4's are Colts but they just lost their contract.
the military is cunducting new weapon trials and so far the FN M4 with a gas piston looks like the winner unless the SCAR gets it

If your Bushmaster performs to your satisfaction than your GTG.  Colt and FN are the current manufacters of the M16 for the Armed Services.  Generally a service member will not keep the same weapon during their time in service unless they are only in one unit and for a short time.  Weapons are assigned to the unit and when you move you get a different weapon assigned.  War soveniors are a touchy subject and changes depending on who is on duty at customs, regs for OIF/OEF.  You can NOT take weapon parts off your weapon for personnal use but not to say that it hasn't happened.  Majority of the troops get issued the optics that they carry now days.  Some still purchase their own and if their commanders allow it, they get to carry it.

CD

Iraq 91,03,04,05,06,08,09
Afghanistan 09,10

as others have said-m16a4's- like current in the Marines- FN's
M4's- Colt
M16A2's- can be newer FN, slightly older colt, or in many cases old A1 lowers with new A2 uppers attached- could be colt ,fn,balimoy,h+r,hydramatic.
as far as issue gear, yes you pretty much get stuck with what they hand you, although RHIP exists and higher ranks usually get a better choice.
A variety of optics are issued (acog/eotech/aimpoint) and some troops do add personal optics as well. Some units do not mind if you add personal stuff to rifles but others are pretty strict about it.

Ok, another question.   What is the difference between the M16 and the M4?
I guess I always thought the M16 was a family of guns, while the M4 was more of a model.  Like, the M4 was a short 16" or less M16/AR15.

Also FN is an acronym for?

Actually the family of guns is the AR-15 ("AR" for Armalite, the original manufacturers).  The M16 is the original design, 20" barrel, rifle length gas system, fixed A1/A2 stock, and rifle length receiver extension and buffer/spring.  The M4 is the newer version with the 14.5" barrel, carbine length gas system, collapsible stock, and carbine length extension and buffer/spring .  There are variations of each (i.e. M16A1, M16A2, M16A3, M16A4, M4A1, M4A2, etc.), with the differences being things like stock length, handguard shape, fixed carry handle vs. flat-top upper, and full-auto vs. burst FCG.

The M16 is a 20" bbl, 1:12 twist, semi & full auto, fixed sights, no foward assist, triangluar handguards
XM16E1/M16A1-20" bbl, 1:12 twist, semi & full auto, fixed sights (hence refered to as A1 sights), foward assist, triangluar handguards
M16A2-20" bbl, 1:7 twist, semi & 3rd burst, adj sights (hence refered as A2), foward assist, round handguards
M16A3-20" bbl, 1:7 twist, semi & auto, adj sights (A2), foward assist, round handguards
M16A4-20" bbl, 1:7 twist, semi & 3rd burst, detachable carrying handle with A2 sights, foward assist, round handguards
M4 Carbine- 14.5" bbl, 1:7 twist, semi & 3rd burst, detachable carrying handle with A2 sights, foward assist, collaspable stock, round handguards
M4A1 Carbine- 14.5" bbl, 1:7 twist, semi & auto, detachable carrying handle with A2 sights, foward assist, collaspable stock, round handguards

FN stands for Fabrique Nationale de Herstal  which has a plant in the US known as FNH USA.

CD