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timothyj999 05-22-2013 12:19 AM

Lower receiver for .223, 6.5, 6.8, 7.62
I have a couple of spare lower receivers and would like to mate one with an upper assembly of a different caliber. Can anyone tell me which other calibers will work with a standard .223 receiver? I know .308 is out, but how about 6.5, 6.8 Rem, or 7.62 x 39? Thanks all.

Sniper03 05-22-2013 12:28 AM

The other calibers you have mentioned beside the 308 which will not work on the Standard AR-15 Lower. I know the 6.8, 7.62 X39 and the 6.5 uppers will work fine but will use a different magazines. Also believe it or not, the big 458 SOCOM uses a standard 5.56 magazine and will work fine on the standard lower receiver. As you stated, the 308 and 243 receivers are much larger with larger bolts and carriers as well as other parts. Sounds like you are good to go.


MisterMcCool 05-22-2013 12:42 AM

They even make .50 BMG uppers for the AR-15.

AgentTikki 05-22-2013 03:30 AM

The numbers are not enough.

6.5 grendel will work
6.5 creedmore will not

7.62x51 will not
7.62x35 will

Do you reload?

timothyj999 05-22-2013 12:21 PM

Thanks everyone for your quick responses. I'm leaning toward 6.5 Grendel

timothyj999 05-22-2013 12:24 PM


Originally Posted by timothyj999
Thanks everyone for your quick responses. I'm leaning toward 6.5 Grendel

Sorry, hit send by mistake.

I'm leaning toward 6.5 Grendel because I want something with more punch at long range. Now I just have to find a place that has some in stock!
Thanks again.

AgentTikki 05-22-2013 04:45 PM

Look at for a nice stainless barrel. IIRC they have 24, 20, 18, 16" in 2.64 LBC (6.5 grendel). But honestly I wouldn't even bother with anything shorter than 20" if you are going for 1000 yards.

ARPerformance also makes a 264lbc very nicely priced at $200, ish when they have them in stock. My friend has a 20# 223 wylde spr barrel than he loves!

Les Bauer also makes a 263 lbc barrel.

Hope that helps ya.

msup752 05-23-2013 12:15 PM

The Grendel is an impressive cartridge. I have a lower just begging for a Grendel upper. I just hate the cost and I shoot 300blk so a 308 bolt gun would make stockpiling reloading equipment easier.
It is tempting to build a 1000 yd ar though!

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