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9/28/2008 6:50:23 AM EDT
I cant find this anywhere so if i missed it im sorry, but will all AR  lowers accept any caliber?IE .223 or 6.8spc,.308?
It seems the the upper is where the diffrence is. I am just starting to venture into the "black rifle" world, and want to build my own, i think i have settled on the 6.8 spc.

9/28/2008 6:52:16 AM EDT
[#1]
regular lowers will handle 223, 6.6, and pistol calibers. It will take a larger lower to handle the 308  and 308-based calibers.
9/28/2008 6:53:34 AM EDT
[#2]
so if i want a 6.8 it will need to be specific to 6.8?
9/28/2008 6:57:00 AM EDT
[#3]
Only if you want it marked 6.8, but a 5.56 standard lower will work just fine with 6.8 uppers and magazines, the only difference is the markings.
9/28/2008 6:59:26 AM EDT
[#4]
thanks, then i can go with the stag 6.8spc lower i was looking at. youu guys are awesome.
9/28/2008 7:26:36 AM EDT
[#5]
It is based on what will fit in the magwell/magazine size.  308 length will not fit.  6.8, 6.5G, 300 whisper etc, are designed to be no longer than 5.56 length, thus will feed thru mags in the magwell.  

Without the magwell constraint, 50 bmg is fired from AR15 based receivers as the lower is used as just a trigger group and mount for the grip.
9/28/2008 8:11:54 AM EDT
[#6]
You need an AR-10 for the .308

There is a list of calibers that will work in the AR-15 here:

www.ar15.com/forums/topic.html?b=3&f=118&t=306487
9/28/2008 10:12:08 AM EDT
[#7]
i just randomly through the .308 cal. , mainly i am intrested if the 6.8spc and the .223 were the same lowers. Which they seem to be. I can have one lower with two uppers and change as my mood fits. The 6.8spc is billed as 80%of the stopping power of the .308. Which is what drew my intrest. I have shot a lot of .223. and really like it but want to be able to reach out to 400-500yrds also.
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