View Full Version : Building an AR-15 5.56

Fygg Nuuton
December 4, 2010, 01:55 AM
So I plan on buying a stripped lower and adding a part or two with each paycheck. Other than a different chamber, is there any difference between .223 and 5.56 parts I should be made aware of?

December 4, 2010, 02:25 AM
No. the only difference i can think of would be whether one or the other parts you might be combining is Mil-spec or not, but that's gonna be a minimal issue i think anyway.
But i would consider a kit to put your AR together, for instance have you looked at Del-Ton? a kit from them will have everything but the stripped lower. you'll save money in the long run rather than buying one or several parts at a time.

Eli W.

Fygg Nuuton
December 4, 2010, 03:12 AM
See, I thought I'd be saving money buying everything separate. Learn something new every day.

December 4, 2010, 04:59 AM
I have priced it out many ways and I could never come out cheaper building it myself than just buying a complete rifle of the exact same specs.

Fygg Nuuton
December 4, 2010, 05:32 AM
The only affordable AR I've seen in my area is an A2, which isn't what I want. the rest are all fancy like, I just want something rugged in case of the zombie apocalypse, ya know? Chrome, 16" barrel. Possibly not even a floating barrel, since that seems to be for competition shooting, I doubt I really need that. But, that is to be researched.

December 4, 2010, 05:59 AM
Buying the complete upper kits is the way to go. Their was some hot black friday deals, You could Beowulf it... Or 6.5 Gren is a nice round.

December 4, 2010, 08:45 AM
Buying the complete upper kits is the way to go. Their was some hot black friday deals, You could Beowulf it... Or 6.5 Gren is a nice round.

Prices are falling like a rock. I saw Aero Precision forged lowers at $75 yesterday. LPK's for $49. The stores are full of AR's, the warehouses too. I think the prices well continue to drop.

December 4, 2010, 02:45 PM
The difference bwtn the .223 and the 5.56, is you can shoot .223 in the 5.56 gun but really shouldn't shoot 5.56 ammo in a .223 gun. Buy a 5.56 chambered gun.

December 5, 2010, 07:40 AM
Just buy quality parts and you won't have any problems. The barrel actually determines whether or not you can shoot 5.56. If the barrel is spec'd for it, you won't have any problems.

As far as the lower itself is concerned, just buy one from a known manufacturer (and don't cheap out). I think you can get Spike's "blemished" lowers for less than $100. It might be a little scratched up, but it's still a Spike's lower, so it's okay. I also won't waste money on a billet lower because it won't provide any better functionality than a forged lower.

Further, if you're going to buy a part or two each paycheck, do NOT buy a lower-parts kit unless you're willing to settle for the hard parts it comes with (I learned that the hard way, and could have saved myself $40 if I had known ahead of time). You'll likely end up replacing the trigger and the pistol grip at the very least. If you *do* get a LPK, void the one from DPMS, the roll pins are over-sized and difficult to install.

December 5, 2010, 07:53 AM
Sorry, sorta derailing the thread, but I'm baffled. All of my loading manuals regard the 5.56 & 223 Rem as exactly the same cartridge, yet I keep running into this 'chamber difference' thing. For identical cartridges, what is different about a chamber for 5.56 that will work for both but not the reverse?

December 5, 2010, 08:12 AM
Technically, 5.56 has a little higher pressure, and a slightly larger chamber, and a longer leade (freebore). So 223 can fire in a 5.56 chamber, but not the other way. Practically, it often does not matter. However, there are reports of Federal XM193 5.56 ammo showing some pressure signs in 223 chambers, namely, the primers pop out on firing. There is an intermediate chamber, called 223 Wylde, that can shoot both.


December 5, 2010, 10:01 AM
Some nato 5.56 has a longer OAL and needs a longer leade than is spec in a .223 chamber. This would jam the 5.56 bullet into the lands of the .223 and may cause an over pressure.

December 5, 2010, 05:41 PM
Building an AR is ideal for the guy buying parts here and there when getting a paycheck. I wouldn't go with the kit guns, just a quality stripped lower then a quality LPK (at least Stag) and a quality milspec receiver extension/M4 stock kit like BCM sells.

Once the lower is done then it's best to buy a complete upper and a BCM or Spikes 16" midlength is ideal. Then sights, sling and maybe rails (though the MOE or even stock handguards are fine for many applications.) Then optics if you want them. And then the really expensive things - training and ammo!