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Posted: 7/18/2008 10:39:46 AM EDT
Can I use anything other than .223 to complete another build with this lower? ie..7.62x39 or ? Please elaborate a little...


Link Posted: 7/18/2008 1:48:19 PM EDT
Your upper and choice of cal is not limited by the lower. You can build or buy an upper in 7.62x39 or .50 Beowulf, or .458 SOCOM, etc and mate it to the lower with no issues.

With the exception of some 9mm set ups, the lowers are the same reagrdless of the upper. The trigger/hammer set up is all the same except some 9mm set ups.

Many folks have one lower and switch out various cal uppers at will with no modifications to the lower.
Link Posted: 7/20/2008 8:46:59 PM EDT
Ok, cool, then I was a little confused...I thought that I would not be able to build a 308 using the lower that I have...I thought that it would not work...

Still not sure what I want to do with this one...I have a 16" AR now, so I am really leaning towards something with a 20 or 24" barrel, for some reach out and touch someone shots!

Any Suggestions?? Anyone...

Link Posted: 7/21/2008 8:39:41 AM EDT
You can not do a .308 using a 5.56 lower, however most of the other caliber choices can be used with your existing lower.
Link Posted: 7/21/2008 8:50:16 AM EDT
5.56mm overall length is 2.250" and 7.62mm overall length is 2.810" so the 2 receivers have different sized magwells. If you want to build an AR in whichever caliber you have to check to see if the caliber you want will fit within the magwell size between the 2 receivers.
Link Posted: 7/21/2008 9:24:33 AM EDT
So is there a list of builds I can do with this lower? ie different calibers?

I thought about the 308 after I posed, as I didn't think the mag would fit..

Again, I am new to this, so I am learning what I can and can't do...

Thanks for the replies...
Link Posted: 7/21/2008 10:20:20 AM EDT
5.56x45mm (AR-15 receiver)
Basically any cartridge either based off the 5.56mm, or within its cartridge overall length of 2.250". Apart from the barrel being chambered for a different round, the only other parts that may be different would be the bolt and or extractor, depending on the case head diameter . Some cartridges that come to mind are the .17 rem, .204 ruger, .223 rem, 6.5 grendel, 6.8 spc, the .300/221 variants, the .450 bushmaster, .458 socom, .50 beowulf and others. The one thing they all have in common is that their maximum cartridge overall length (COL) is no larger than 2.250".
7.62x51mm (AR-10™ and similar sized receivers)
This receiver has a magwell which accomodates cartridges with a COL of 2.81". The boltface is for the .308 headstamp and basically you can chamber for just about any cartridge based off the .308 win case or falls within the length constraints of the magwell. Some alternate choices are .243 winchester, 7mm-08, .260 remington, .338 federal, as well as some of the .325 WSM wildcats. I think the .284 winchester would be an interesting choice, with bullet choices ranging from 100gr-175gr and velocities ranging from 2900-3400fps at the muzzle for the 100gr bullets and velocities of 2100-2600fps at the muzzle with the 175gr bullets.
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