DIY AR Help

[Pathfinder]

I've looked around and cannot find an answer to this question. 

If you want to build an AR from a lower in other than NATO 5.56mm caliber, can you use a receiver marked 5.56? I am thinking about building a 6.8 and was wondering where to start.

Thanks all.

 

[mnshooter]

The barrel should be marked with the caliber.  It's very hard to find any lowers with a special caliber mark on them.  Most everyone interchanges their upper assemblies in various calibers with whatever lower is handy for their own personal use.
Now if you were going to get in the manufacture and sale of the complete rifle, you would want to find out what keeps the BATF happy.  On second thought, I've never met a BATF agent who I could describe as happy, but they have been polite if not quite to pleasant.  Maybe when they get their new boss he can revive their spirits.  Now, get rid of the unconstitutional '86 ban on automatics, and I'll smile enough for all of them.  Actually, I'll probably need to get my own zip code to handle all the form 1's.

[Bidah]

Pathfinder,

For 6.8 you use a regular 5.56 lower.  You will need 6.8 magazines though.  6.5 Grendel is also on this same lower, as is the .450 Bushmaster, .50 Beowolf, .300 Whisper, and a host of others.

When you move up to .243, .308 and such you need a different lower since the cartridge is longer than the 5.56x45.

-Bidah

[Pathfinder]

It's very hard to find any lowers with a special caliber mark on them.

Well, in my typical ready, shoot aim lifestyle, I already picked up a DPMS lower clearly marked 5.56. That's when I decided maybe to ask someone more knowledgeable.

I had always heard the lower didn't matter, just got a stop when I got the lower last Friday.

Thanks.

 

[DonWorsham]

... I already picked up a DPMS lower clearly marked 5.56.

How is it labeled? My DPMS lower shows:

CAL. 223-5.56 MM
MOD. A-15

[Sponsor]

[Pathfinder]

How is it labeled? My DPMS lower shows:

CAL. 223-5.56 MM
MOD. A-15

Both my DPMS' (one full carbine, one lower) say the same thing as yours.