Need Info about AR Uppers & Lowers

[XxWINxX94]

Hello everyone,
I'm considering purchasing an AR but I have a few questions that require knowledge beyond mine. I would like to "build" my own AR with all kinds of accessories and customizations to make it unique. I understand that AR uppers and lowers are interchangeble and so are some attachments.

QUESTIONS:

1. If I have a complete .223 lower, could I put a 7.62x39 complete upper on and would it be ready to shoot? I know I would also need a 7.62x39 mag.

2. Are the .308 Uppers/Lowers compatible with a 7.62x39 or .223 or vise-versa?

3. If I build an AR from an upper and lower, could I put on a different rail, foregrip, and stock?

4. Is there any type of advice you would give to me when trying to build an Upper/Lower AR?

I found these on Gunbroker:
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=149460708
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=149282369

 

[Texpatriate]

1. If I have a complete .223 lower, could I put a 7.62x39 complete upper on and would it be ready to shoot? I know I would also need a 7.62x39 mag.

Yes, but you will also have to replace the standard .223 bolt with a 7.62x39 bolt. Probably would be best to have a dedicated 7.62x39 dedicated bolt carrier group for the 7.62x39 upper

2. Are the .308 Uppers/Lowers compatible with a 7.62x39 or .223 or vise-versa?

No, the .308 round is too large to fit in a .223 or 7.62x39 magwell.

3. If I build an AR from an upper and lower, could I put on a different rail, foregrip, and stock?

Yes. Various rail systems require different mounting methods. A Danial Defense Omega rail will simply replace the standard AR Handguards, very easy. The Daniel Defense Lite and M4 rail systems, Larue Tactical rails, and YHM rails will require you to remove the front site base, gas tube, and replace the barrel nut with a proprietary one, very doable with the right tools, but not as simple as the Omega system. Other rail systems such as those made by Troy and Midwest Industries will use the standard barrel nut, but require you to cut of the delta ring with a dremel tool or bolt cutters, kind of in between on the level of difficulty for installation.

Foregrips and stocks are easy to replace. Just make sure you use the right size (commercial diameter vs. mil-spec diameter) stock for your receiver extension.

4. Is there any type of advice you would give to me when trying to build an Upper/Lower AR?

Use good quality parts. All parts are NOT created equal. A Daniel Defense, Colt, LMT, or G&R Tactical parts kits are superior to DPMS or RRA parts kits. Bravo Company USA and G&R Tactical are good places to shop for quality parts.

 

[XxWINxX94]

Thanks for the info!

So using a different caliber lower and upper would require purchase of a bolt of the caliber you want to shoot?

And what if I used a .308 lower? Wouldn't the smaller 7.62x39 round fit in there?

 

[Mags]

And what if I used a .308 lower? Wouldn't the smaller 7.62x39 round fit in there?

No a 308 lower is too long for a shorter upper such as 223,7.62x39 or 6.8 to fit.

 

[iamkris]

Here's the rule you need to remember.

You need an AR15 platform for the following rounds. 204 Ruger, 7.62x39, 6.5 Grendel, 6.8 SPC, .458 SOCOM, 450 Bushmaster, .50 Beowulf

For longer cartridges in the 308 class you need an AR10 platform, such as .243 Win, 308 Win, 260 Rem, 6.5 Creedmore, 7mm-08, 338 Federal.

There are a couple of specialty manufacturers making larger platforms (Cobb used to do it at least - don't know if they still do) for 30-06-class cartridges.