Need AR15 Help!


October 3, 2008, 09:24 PM
I am building an AR15. Just started really; I have my lower and a flat top upper and that's it so far. I've been shopping around a lot and I know that I want a 16" barrel probably a standard heavy barrel (don't have any burning desire for a M4 contour barrel because I don't forsee the need for a grenade launcher but I'm not rabidly against it either) with gas block front sight, free float handguards, red-dot type optic, flip-up sights (they will probably have to wait), and probably a six-position stock.

I am relatively unfamiliar with the finer points of the AR as I have never been a huge fan of the weapon. I need to know the difference between an M4 extension and a Standard extension in reference to the barrel.

The other issue I have is the length of the gas system. I understand the difference between the carbine and mid-length systems and that the mid-length would produce less wear. But when I am looking at barrels online I don't see where it is specified carbine, mid or rifle length. Surely there must be a difference in were the hole is drilled if you can have either carbine or midlength in a 16" barrel. Or am I mistaken and is midlength not available in a 16" barrel.

Please help, O Great AR Gurus out there. (And remember, I'm a cop so I'm broke; $1500 weapon systems don't do me any good)

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October 3, 2008, 10:36 PM
if you already have your upper, then it either has two little indentions (feed ramps) next to where the barrel extension sits or it doesn't. if it does, they're called m4 feed ramps and you should ge t a barrel that has them. if it doesn't, then get a barrel with "rifle" feed ramps. (aka standard)

the barrels online should say what type of feed ramp they have and they should definitely say what type of gas. if they fail to mention, i would assume it's rifle ramps and carbine length gas. i would verify verbally before purchasing.

the difference is the angle. m4 ramps cut into the receiver. rifle don't.

you can get good barrels all over the place. denny's barrels from globaltactical are great. noveske sells great barrels. you can buy colt and others on arfcom's EE. cmmg is ok.

if you have a choice, given your 16" requirement, get mid-length gas and m4 feedramps. don't lose any sleep over it if you can't.

what you should get:
chamber: 5.56 or wylde
gas block: depends on what you want
handguards: YHM on a budget, Larue if you want quality
optic: aimpoint micro T1
stock: magpul CTR
BCG: bravocompany's

sounds like you may also need
charging handle
FCG (i.e. trigger/hammer/disconnector)
lower parts kit
gas tube
receiver extension (aka buffer tube)
some flavor of flash suppressor

(edit: btw, i answered the question you asked. my real opinion though is that you should try to sell your upper and lower to someone else and just buy a CD M4-LE. Save up a couple more bucks and put the optic on it. tell your friends/family you want a CTR and magazines for christmas)

October 3, 2008, 10:47 PM
Thank you very much. I have M4 feed ramps and I wanted to get midlength gas system but was unsure if I could get it with a 16" barrel. I am definitely going with the 5.56 chamber (don't think I can afford the Wylde). The grips, lower parts, etc. I pretty well have picked out, but I was unsure about the carbine-midlength question and I had not heard the feed ramps referred to as extensions. I really appreciate your advice and I will have to look into the specific parts you recommend.

October 3, 2008, 10:51 PM
On the barrel extension, you can have M4 cuts if you don't have the grooves on your receiver, the problem comes when you have M4 cuts on the receiver and not on the extension. I bought an upper from that had a M4 receiver with a standard barrel extension and it would jam with one of the older mags I had, most likely because it sat a bit lower than new mags.

The mid-length gas system is for 16" barrels. You aren't going for the M4gery look so I'd say that a mid-length is probably the best way to go.

October 3, 2008, 11:05 PM
I'll have to inspect my upper when it arrives. Hopefully in a day or so. I bought a YHM flat top upper. If you don't mind I would like to send you a message later when about these things when I actually have my upper in hand.

October 3, 2008, 11:05 PM
tarvis is right. it is certainly possible to assemble a gun with m4 ramps in the extension and not on the receiver or vice versa. i would attempt to avoid that.

happy to help. msg all you want

October 3, 2008, 11:42 PM
do M4 feed ramps do any significant good for midlength or full-length systems? I know that they are a very smart choice for carbine lengths due to the more 'aggressive' action and feeding, but what about for longer systems?

October 4, 2008, 12:08 AM
M4 ramps help feed the rd into the chamber. Does it really help? Some say yes, some say no. But IMO they certainly couldn't hurt.

Lose the heavy barrel. It's not needed.

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