I have a colt sporter match hbar 16" carbine w/1/9 twist, and I hear alot about the m4 whats the big deal about them, the only difference that I can tell is the barrel has that jog in it for the 203 launcher, and I heard the ramp inside the chamber is different! other than the fact the navy seals carry them what's all the hype about ? also on the discovery channel I heard that the navy seals carry a 727 it looks just like an m4 why do the call it a 727 ? please educate me thanks in advance. [>:/]    

I think you've answered your own question [;D]

havoc,
Proud owner of a KAC SR-15 [b]M4[/b]

A pleasant side effect of those "jogs" in the barrel is that the weight distribution is favorably altered, in my opinion, and the weapon just seems to have an inherently more comfortable balance to it.  

I also have a Colt MT6731 16" HBAR and while I like the gun, it just doesn't seem to fit me like a glove as does my M4gery. There does seem to be intangibles involved, too. Maybe it's just one of those things you have to try before you understand it.

An HBAR barrel is a HEAVY barrel. The M4 barrel is "skinny" under the hand guards and therefore has less mass and weight.

The M4 ramps are not "inside the chamber", but they are cut into the aluminum upper receiver just before the ramps that are cut into the steel barrel.  These ramps supposedly provide greater feeding reliability with fully automatic fire.

The M4 barrel is not 16" like your HBAR.  a true M4 barrel is 14.5" and is illegal to own by a civilian unless the rifle is registered with the BATF as a class III machinegun or a pistol/short-barreled-rifle.  Civilians with 14.5" barrels on non Class III or SRB guns must have a permanently attached muzzle device that extends the barrel length to 16"

The M4 also a has larger and more "blocky" looking handguard with 2 layers of aluminum heat shielding instead of 1 layer like skinny AR15 "shorty" handguards. (See the handguards on the rifle that is in the logo at the top of this web page.)  M4 handguards are much better looking in my opinion.  They also help protect you from a hot barrel after full-auto fire.

I've seen a picture of an M4 rear sight that was calibrated for 300 to 600 meters instead of 300 to 800 meters like the M16A2.  The web page where I saw this picture is down right now, but I think the link was [url]http://m4carbine.homestead.com/[/url]

True M4 carbines are obviously fully automatic as well.

The best Post-1994 M4 civilian look alike rifle is the AR15.com limited edition group purchase rifle, in my humble opinion.

Take a look at this and tell me if you think it doesn't look bitchin':

[img]http://albums.photopoint.com/j/View?u=966303&a=7081245&p=49650138&Sequence=0[/img]

I agree. Those skinny handguards do heat up very quickly even if you are shooting somewhat quickly in semi.  I have not yet tried the larger M4 handguards, but to me seems like a worthwhile equipment.

I'll be trying the larger handguards just as soon as my AR15.com LEGP rifle comes in!

One thing i still haven´t grasped is, why does the new RO921HB barrels have to have those cuts there. An M203 went nicely on to my BM M4 Carbine. Is it just with newer M203s?.

Thanks for the barrel pix Boland.  Is that M4 yours?

other than the fact it looks cool what would you use a grenade launcher for :/ and Iwant one of those barrels is that a colt thing or what ?

socum heavy barrel that is

Whadya mean what would you use the grenade launcher for?? Anyway, Boland pretty much hit it on the head. Also, the M4HB is designed to help prevent cook-offs from long bouts of automatic fire... You can start to expect cook-offs in the neighborhood of 421 rounds of sustained full-auto [;)]

I learned to never start a topic with "What's the big deal...". Glad to see they're going easy on ya.

Thanks for the answer Boland. My M4 is the light profile. Now that i think about it, the M203 was tight to go on it. Should have thought better.
I purchased my Bushmaster M4A3(exactly like a M4A1  except it is semi only) with a reasonable price and here in Finland there is a shortage of M4s, by any manufacturer. So i have gotten pretty good offers on it, but im not going to sell it.