Alright, I know this has been addressed about 450 times on this site, but I'm gonna ask again, cause I'm a jackass...  I'm interested in a 16" CAR kit from JT, but they offer the chrome lined barrel in M4 only (I know this is gonna change soon, so not the biggest concern).  What are the differences and Pros/Cons of each.  I like the way the M4's are ramped.  What else is different.  Thanks for answering this AGAIN.

Upper receiver style, barrel profile, handguard diameter.

What's different on the reciever (guessing M4 is an A3 style stock?), Barrel difference?  Is the M4 larger or smaller than standard CAR?  I'm pretty sure the M4 handguards are a little bigger around and a little shorter,right?  So again, I'm gonna guess the bigger handguards would dissipate heat better, the slimmer barrel would not(?) hold up as well, and the receiver depends on what you like.???  Just trying to decide whether to go with the M4gery or wait till they offer a 16" chrome CAR.  The M4 is a little more expensive and I was wondering what benefits the M4 has over the standard CAR.  Thanks for the response....

Let me see if I can help you. The terms “CAR” and “M4” have taken on a life of their own.

Years ago CAR was used to describe any Carbine AR-15 / M16. This includes the 11.5 inch XM177 type barrels all the way out to the light weight 16 inch barreled “Carbine” AR /  M16. I do not know the year that Colt started using the term “CAR” as a marketing tool but that is where it originated and how the term was / is used.

This is about as close as it comes to a CAR.
[img]http://www.colt.com/law/images/ar15a2.jpg[/img]

Then came along the Abu Dhabi (sp?) “Carbine” project in the 80’s. This rifle became the M4. The M4 came from the US Army as it is fourth “Carbine” the Army has adopted. The only “real” M4’s are made by Colt. They have the following characteristics:
1. 14.5 inch barrel, 1/7 twist, extended feed ramps on the barrel extension, barrel profile similar to that of the M16A2 with the addition of a turned down portion nearly half way between the front of the front sight tower and the flash hider (this was done to accommodate an M203 40mm grenade launcher)
2. Larger oval shaped front hand guards with double heat shields. These hand guards do not assist is cooling. They were designed with the intent of helping keep the hand guards cooler to the touch under sustained fire.
3. Extended feed ramp cuts in the upper receiver that match up to the extended feed ramps on the M4 barrel extension. Most “real” (Colt) M4 uppers have a 4 or M4 stamped in front of the upper just above the gas tube hole. Colt has made M4 uppers with A1 sights (like the C7 uppers), A2 uppers and A3 or flat top uppers.

Here is a pic of an M4
[img]http://www.colt.com/law/images/m4.jpg[/img]

Now a lot of companies sell barrels and complete uppers that they call “M4”. Usually the only thing that is M4ish about them is the barrel profile. It looks like an M4 barrel but that is about as far as it goes. This is one of several reasons you see such high prices on the Colt M4 uppers, they are the real deal. CMMG has had some M4 uppers made by DPMS that are as close as you can get to the real deal.

Thanks, that helps.  Now, I have seen posts of the feed ramps on this site, does anybody know if JT's M4gerys are ramped, or if they just have the M4 profile...?  Seems to be the only real benefit to me, otherwise I'll wait for the chrome lined 16" reg barrels and just get their standard CAR kit.  Thanks again for the description Lucky.

Drop them a line in the industry section and ask.  I have a Colt AR15A3 that has the same M4 ramps, it isn't a big deal.

I should have mentioned that starting a few years back Colt has put the M4 feed ramps on all of their carbine uppers and barrels. I have a 16 inch light weight with the M4 barrel extention. When your buying Colt uppers you need to specify carbine or rifle because of this issue.

J&T's do not have the M4 feedramps.  At least mine wasn't, things may have changed by now.  Nor was the barrel chrome-lined; its "chrome moly" metal.   Make sure you know exactly what you get when they say, "Its a chrome Wilson match grade barrel."   And don't get confused too that [url]www.wilsonarms.com[/url] is not the same as [url]www.wilsoncombat.com[/url] .

All the barrel had M4-ish was the front step down cut.  Underneath the handguards, it was normal Hbar profile.  Here's a pic of my actual barrel next to a real Colt, with its factory side sling swivel attachment:
[img]http://www.boomspeed.com/kisara/KisarasMockM4.jpg[/img]

Don't get me wrong, the J&T was a very accurate upper, I loved it, but eventually sold it.  Their quality and service was great, and the price was fantastic.  Buy what you can afford, but just make sure you know what you are getting.   Do your research.