AR Build info/help...

[Tgoody14]

I have been reading up on all the forums (ar-15, m4carbine, chatterbox, and here...) for about a week straight trying to get ready for my 1st build. Figured I keep my questions for you guys (my local forum)

Little background:
1st Ar was an Olympic Arms - Sold
2nd BushMaster Carbon15 - Feed Problems/Sold
3rd Colt 6920 - Current Rifle and I also carry one of these on duty. I have my personal 6920 rigged up for long range/coyote rifle and it drives tacks at 200 yards.

What I'm looking to do is to build a 14'5 barrel, low profile gas block, with a Colt lower (YES, I drink the juice... Haha) This will be my close range/on the 4wheeler/ridin the farm rifle

So my questions are:

1) If I can't find a complete Colt lower, what other brands are compatible on kits for a stripped Colt lower? Am I right in thinking that as long as it is "Mil Spec" it will work? Or are some "Mil Spec" not really Mil Spec...

2) Also, is this the same for the Upper (mil spec)? What brands for an upper and barrel will be compatible with my Colt lower?

3) If you have some useful links that you think I could benefit from reading please post em up

4) If you have a Colt Lower or know where I might find one, please post as well!

Thanks in Advance guys!

 

[jtw2]

essentially anything that has a description of "large pin" should work. You can also get some small to large pin adaptors and then anything will work. I've gone that route but honestly it's a pain in the ass to take it down.

 

[Shorts]

OP, GandRTactical has complete lowers, both BCM and Colt. You can pick up uppers from Grant as well. Or order a complete upper from BCM. Both the best options IMO if you want guaranteed milspec without a second thought. You said you drank the koolaid and if you've been reading M4C then you have already heard the things I mentioned.

 

[Tgoody14]

jtw2 - thanks for the info

OP, GandRTactical has complete lowers, both BCM and Colt. You can pick up uppers from Grant as well. Or order a complete upper from BCM. Both the best options IMO if you want guaranteed milspec without a second thought. You said you drank the koolaid and if you've been reading M4C then you have already heard the things I mentioned.

Yea GnR is out of stock on everything. I almost sent them an email just to see what kind of time frame Id be looking at for a Colt complete lower. BCM is probably my first option for the upper as well.

I just want to make sure and stay away from whatever brands you guys know that I'll run into problems so I don't waste any money.

Thanks for info

 

[Shorts]

No way, I just looked doing a little dreaming/shopping. Could have sworn there were still lowers there. I was looking at stripped lowers. Maybe that's why I'm thinking they were in stock.

Oh here's one:
Colt Magpul Lower
Colt 6920MP Magpul Lower at G and R Tactical


The BCM is a good deal and a solid choice. I've grabbed one of these and would recommend, (not purchased from G&R though):
BCM Lower at G and R Tactical


I've seen this LMT lower recommended before but can't vouch for it personally:
Rainier Arms™ | Browse | Receivers - Lowers | LMT Defender 2000 Lower


I'll keep my eye out and post it up. Send Grant an email, I'm sure he knows what's coming in and can at least forecast for you.

 

[Tgoody14]

No way, I just looked doing a little dreaming/shopping. Could have sworn there were still lowers there. I was looking at stripped lowers. Maybe that's why I'm thinking they were in stock.

Oh here's one:
Colt Magpul Lower
Colt 6920MP Magpul Lower at G and R Tactical


The BCM is a good deal and a solid choice. I've grabbed one of these and would recommend, (not purchased from G&R though):
BCM Lower at G and R Tactical


I've seen this LMT lower recommended before but can't vouch for it personally:
Rainier Arms™ | Browse | Receivers - Lowers | LMT Defender 2000 Lower


I'll keep my eye out and post it up. Send Grant an email, I'm sure he knows what's coming in and can at least forecast for you.

Yea I saw that one, but I'm not really a big fan of Magpul stuff.

I actually just ran across a complete Colt lower that just got thrown up on M4C an hour ago! Talk about timing!!!! Prolly going to pick it up and go from there. Just need an upper, barrel, and rails now!

Are there any restrictions on barrel length? Is 14'5 as short as I can go without a stamp? Saw a real nice 12.5" barrel with 10" rails, looked sharp! Exactly where I'm wanting to go with this build...

 

[Shorts]

That is good timing (and how I came upon the BCM lower one Saturday morning)

Yup, a 14.5" is the shortest you can go without going the NFA route. You will need the muzzle device pinned and welded. IMO you don't gain much in that configuration over a 16". Instead I feel some "modularability" is lost because the pinned MD limits the work you can do to the upper. Likely you've already considered this and I respect your decision to go with it. Also on the 14.5" double check the length of the MD that it is long enough to bring the OAL over 16".

I'd like to get to get a 11.5" length. I hear you on the SBRs with full rails looking good. They have good proportions

 

[M. Sage]

That is good timing (and how I came upon the BCM lower one Saturday morning)

Yup, a 14.5" is the shortest you can go without going the NFA route. You will need the muzzle device pinned and welded. IMO you don't gain much in that configuration over a 16". Instead I feel some "modularability" is lost because the pinned MD limits the work you can do to the upper. Likely you've already considered this and I respect your decision to go with it. Also on the 14.5" double check the length of the MD that it is long enough to bring the OAL over 16".

I'd like to get to get a 11.5" length. I hear you on the SBRs with full rails looking good. They have good proportions

And for the ATF's sake, make sure the muzzle device is pinned and welded BEFORE you take possession. As far as the feds are concerned, a complete AR rifle and a <16" barreled upper in your possession equals an SBR. I know it's stupid, but it's how federal LE works (stupidly).

 

[Tgoody14]

I still can't decide whether I want to go 14.5 or 16. Any real deal breakers between these 2 lengths!? (Besides the pinned flash hider)

I know for sure I want to go with at least 12" rails, maybe longer if I go 16 on the barrel. I want to keep this as lightweight as possible. Like I said in my 1st post, I already have a heavy long range set up so this will be more for mobility/close range! I shoot 64 grain ammo if that matters.

Any info is appreciated. Thanks!

 

[Big Phil]

For rails the keymod is the new "hot" thing, I have a Noveske NSR, however I just got my Centurion CMR and I am very impressed. The CMR has holes that are already tapped for their screws and accesories. Supposedly the new BCM keymod rail is lighter than the Noveske. Which weighs 11 ounces for a 14 inch rail.

As far as the quality of forged uppers/lowers what you're really paying for is how well a particular company mills and anodizes the receiver.

The reason is, there are only 17ish (can't remember the exact number) that actually forge the uppers/lowers. From there they are sent as nothing more than a paperweight to all the different companies, big and small. Some companies have rejects, often called 2nds, that aren't up to snuff in appearance but are perfectly functional. Some companies like Noveske will reject uppers that you have to look hard to find an imperfection, whereas another company would not reject it.

In general most forged uppers and lowers are the same, however companies like BCM, Daniel Defense, Colt and Noveske have made a name for themselves by only accepting the very best uppers and lowers.

Billet is a whole other story, but the cost/benefit ratio really isn't that big a deal for me. I haven't found billet receivers to be any more accurate or functional than forged. The cost is generally much higher but you can get more of a "custom looking" AR that way.

Just as an FYI, Colt trigger pins are .169 inches while most other companies use .154 in. pins, as far as I know. This won't affect you as it pertains to quality, only the choice of a few (not many) aftermarket triggers. That is if you're into that kind of thing.

As far as barrel length, I prefer 14.5, no scientific data just preference. It just feels right.

Hope that helps.

 

[grumper]

Colt 6920s were switched to standard sized trigger and hammer pins some time in 2009.

I've read while they were making the switch they had some leftover guns with large pins and others standard sized in the same batches. Anything new you buy will have the regular pins though.

 

[Tgoody14]

Phil - great write up and info. I'll look into those rails

Grumper - I have the complete 6720 lower, not sure which year yet

I think I've decided to go with a 16" lightweight mid length barrel then 13-15" rails. Mainly since this will be my first build I'd hate to limit myself with a pinned flash hider. I want to be able to swap things in/out until I figure out what I like best

I really like the look of this set up... 16" barrel with 15" rail

This is the complete set up I'm working towards...
16" barrel, 15" rail, going FDE minus upper and lower receiver

Any opinions on lightweight mid length uppers/barrels?

 

[Big Phil]

Mid length with a VLTOR A5 buffer system.

 

[Shorts]

I see no reason not to go 16" LW. BCM's profile of LW barrels is the lightest I can find specs for. Colt are light as well. When you look at specs of barrels that are "LW" ask to see the profile measurements. There is not a standard profile spec'd for LW and every manf is a little different. It can mean the difference of up to 4oz, but more realistically ~2oz between LW barrels. I haven't been able to find profile specs for any other brands so if anyone here has them, please post them up.

BCM LW 16"

Adco'd WW to LW spec'd

WW M4 profile

 

[Tgoody14]

Wow! You guys are great! Lots of good info here!
Thanks Shorts!
Next question, with me wanting to be able to go with extended rails...

Should I go with a lw barrel and:
1 - shave the FSP down
2 - swap it out with a low profile gas block
Or just purchase a lw barrel with a lpgb
Any advantages or disadvantages?

I still haven't completely ruled out the 14.5 with 13" rails! They sure look niiiiiice... If I did go that route still with a pinned flash hider and a lpgb, would I still be able to swap out different rails whenever the time comes or once that flash hider is pinned am I stuck with what I got???

Thanks again for all the help! I like picking your brains!

 

[Big Phil]

A shaved front sight post is thought to be more solidly attached via roll pins. I generally use a low profile gas block.
The only "problem" with a shaved front sight base is the time it takes to shave it down but it can easily done with a Dremel.
I've only seen one rail that doesn't work with some lopro gas blocks and that's the Centurion CMR. But 5 minutes with a Dremel will fix that.

 

[Tgoody14]

Good to know Phil! Thanks! And that 14.5 you put up in the classifieds awhile back is SHARP!!

You got me wanting to go back to the 14.5

It's all just a vicious cycle haha

I found a 14.5" with a pinned FH that I like on another forum, but I didn't like the rails and didn't know if I'd be able to swap them out if I picked that one up...

If I got the 16 and had to shave it down that would not be a problem! The ole lady just got me a gift card to Home Depot for Christmas..

 

[M. Sage]

FWIW, I've never had a problem with set screw gas blocks. I just changed from adjustable back to a regular low profile and the screws had tightened themselves down through heat expansion/contraction to the point I was worried I'd have to drill them out. IMO the only real good argument for pins is to keep Joe from doing stupid things with his issue weapon.

There might be a way to get raw numbers from this, but I don't know. At any rate, it might be a helpful resource for you. AR-15 Weight Calculator

 

[Big Phil]

I love the 14.5 by it's usually a one and done kind of thing. To swap rails you need to be able to get the barrel nut off to do that you need to get the gas block, tube and muzzle device off.

I say usually because I talked to a guy who said he had done it before. I have no first hand experience.

My advice is, if you think you might want to try different rails or muzzle devices in the future just get a 16". Also go ahead and invest in a vice and the receiver blocks now it will make life WAY easier for future builds.

 

[Tgoody14]

Once again I want to thank everyone for the abundance of information! Much appreciated! After spending MANY hours researching pros/cons, reviews, prices differences, etc...

I decided on a 14.5". I actually found a complete upper exactly to how I would have set it up if I would have gone part by part. Although I feel as if I cheated the whole "build" process by getting a complete upper and lower, it was still a great learning experience.

I also decided that it was so much fun learning/reading about the entire process of everything involved that I have come to the realization that there's no need in letting all this info go to waste haha. I'm going to build another AR, but from complete scratch this time and not already assembled uppers/lowers. May even go with a 20" ss barrel on the next one.

I'll get some pis put up for this current set up as they arrive.

Thanks again!