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1/22/2020 12:12:56 PM
Posted: 9/19/2009 12:26:56 PM EST
I just picked up a RRA mid-length upper at a gun show on the assumption it is 5.56. But the paperwork says 6.8 SPC. WTF???

I have no experience with 6.8 SPC, but I slipped a spent round of 5.56 in the chamber and it fit snug enough I had to push it out with a cleaning rod. There's no way 5.56 brass should chamber snugly in a 6.8 chamber ... right?

Like I said - no snickering allowed. There are no markings on the barrel or upper except the Cerro keyhole, and nothing under the handguards except a funky little punch mark that looks like "MK". Wouldn't a 6.8 upper be marked as such?

Reassure me, lads.

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Link Posted: 9/19/2009 12:31:56 PM EST
Go buy a box of 6.8 and see if it fits
Link Posted: 9/19/2009 12:34:10 PM EST
There should be engraving on the barrel telling you exactly what type of round it was made for...
Link Posted: 9/19/2009 12:34:58 PM EST
Pull the bolt carrier group. Place a cartridge against the bolt. If the 5.56/223 is smaller than the recess in the bolt face... it probably is a 6.8.

Link Posted: 9/19/2009 12:52:49 PM EST
Sounds like someone used the 6.8 lower to build a 5.56 (if that's what it turns out to be).

The lower is logged on the 4473 according to the upper it wears when it is sold. If it was later rebuilt as a 5.56, there would be no record of it.

Link Posted: 9/19/2009 12:58:19 PM EST
check your 5.56 ammo against the boltface. If the boltface is larger than the ammo your in trouble
Link Posted: 9/19/2009 1:02:12 PM EST
Originally Posted By xpired:
There should be engraving on the barrel telling you exactly what type of round it was made for...


Not. Like I said, I even pulled the handguards and it's not marked. But neither was the other RRA I had, and it was a factory rifle.

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Link Posted: 9/19/2009 1:03:09 PM EST
Originally Posted By DasRonin:
Pull the bolt carrier group. Place a cartridge against the bolt. If the 5.56/223 is smaller than the recess in the bolt face... it probably is a 6.8.



Yeah, I did that and it's 5.56 sized. Liek I said, I don't what a 6.8 cartridge even looks like, but I'm sure the dimensions of the case are different.

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Link Posted: 9/19/2009 1:12:09 PM EST
They gave you the wrong paperwork. RRA marks thier 6.8 as 6.8 on the side of the upper. I have thier middy, and it's heavy under the HG's also. A 5.56 would be noticably loose in a 6.8 chamber.
Link Posted: 9/19/2009 1:20:58 PM EST
Originally Posted By TerryC:
Sounds like someone used the 6.8 lower to build a 5.56 (if that's what it turns out to be).

The lower is logged on the 4473 according to the upper it wears when it is sold. If it was later rebuilt as a 5.56, there would be no record of it.



Nah - no hanky-panky going on. These folks are a big dealer and they stock all sorts of lowers and uppers, as well as parts and complete guns. This was just an upper.

I've been able to talk to the dealer at the show and the guy said he just wrote it up wrong. Said if it were 6.8 it would say so prominently on the upper.

Base diameter of the 5.56 is .377", while the 6.8 is .421. I figure a 5.56 case would rattle around in the chamber of a 6.8 - at least enough to allow it to drop out without having to push it out with a cleaning rod.

I guess I'm satisfied.

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Link Posted: 9/19/2009 1:30:31 PM EST
[Last Edit: 9/19/2009 1:32:31 PM EST by MikefromTX]
Originally Posted By Balforin:
They gave you the wrong paperwork. RRA marks thier 6.8 as 6.8 on the side of the upper. I have thier middy, and it's heavy under the HG's also. A 5.56 would be noticably loose in a 6.8 chamber.


Yep, this is apparently what happened. The guy at the show apologized and said he was just too busy and not paying enough attention.

Thanks for the confirmation of the upper markings.

ETA - After trying spent brass in the chamber, I just dropped an unfired round into the chamber and once again had to use the cleaning rod to dislodge it ... and it wasn't even chambered by the bolt - just dropped in. Too tight for a 6.8!

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Link Posted: 9/19/2009 1:44:59 PM EST
Originally Posted By MikefromTX:
Originally Posted By TerryC:
Sounds like someone used the 6.8 lower to build a 5.56 (if that's what it turns out to be).

The lower is logged on the 4473 according to the upper it wears when it is sold. If it was later rebuilt as a 5.56, there would be no record of it.



Nah - no hanky-panky going on. These folks are a big dealer and they stock all sorts of lowers and uppers, as well as parts and complete guns. This was just an upper.

I've been able to talk to the dealer at the show and the guy said he just wrote it up wrong. Said if it were 6.8 it would say so prominently on the upper.

Base diameter of the 5.56 is .377", while the 6.8 is .421. I figure a 5.56 case would rattle around in the chamber of a 6.8 - at least enough to allow it to drop out without having to push it out with a cleaning rod.

I guess I'm satisfied.

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My bad. When you said "gun show" I assumed it was a used AR, a complete rifle. I totally missed the part about it being just an upper.

I guess it's true what they say about when you ASSume...

If it's just the upper then the paperwork snafu is no biggie.

Link Posted: 9/19/2009 2:00:18 PM EST
RRA 6.8 uppers have 6.8 SPC engraved above the ejection port in big bold letters. If it doesn't have this then something is wrong.
Link Posted: 9/19/2009 2:37:28 PM EST
I would think you should be able to tell just from looking at the bore diameter.
Link Posted: 9/19/2009 3:34:40 PM EST
Originally Posted By reelserious:
RRA 6.8 uppers have 6.8 SPC engraved above the ejection port in big bold letters. If it doesn't have this then something is wrong.


LOL. No, something is RIGHT if it's not there, since a 5.56 is what I wanted!

But I appreciate your confirming the markings.

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Link Posted: 9/19/2009 3:40:00 PM EST
Originally Posted By Captains1911:
I would think you should be able to tell just from looking at the bore diameter.


Well, that's actually the first thing I looked at after checking for markings. It LOOKS like .223/5.56 to me, but then, I've never seen a 6.8 before!

I'm not sure I could eyeball the difference between .223 and .276 bore diameters, anyway, especially looking down through an A2 flash hider.

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Link Posted: 9/19/2009 3:59:22 PM EST
Originally Posted By MikefromTX:
Originally Posted By reelserious:
RRA 6.8 uppers have 6.8 SPC engraved above the ejection port in big bold letters. If it doesn't have this then something is wrong.


LOL. No, something is RIGHT if it's not there, since a 5.56 is what I wanted!

But I appreciate your confirming the markings.

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Ah, no LOL 6.8 is what you want.

Link Posted: 9/19/2009 3:59:47 PM EST
Originally Posted By MikefromTX:
Originally Posted By Captains1911:
I would think you should be able to tell just from looking at the bore diameter.


Well, that's actually the first thing I looked at after checking for markings. It LOOKS like .223/5.56 to me, but then, I've never seen a 6.8 before!

I'm not sure I could eyeball the difference between .223 and .276 bore diameters, anyway, especially looking down through an A2 flash hider.

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or try running a 5.56 bore brush thru it and see if it's tight or not.
Link Posted: 9/19/2009 4:54:00 PM EST
Originally Posted By MikefromTX:
Originally Posted By DasRonin:
Pull the bolt carrier group. Place a cartridge against the bolt. If the 5.56/223 is smaller than the recess in the bolt face... it probably is a 6.8.



Yeah, I did that and it's 5.56 sized. Liek I said, I don't what a 6.8 cartridge even looks like, but I'm sure the dimensions of the case are different.

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left 6.8SPC, right .223
Link Posted: 9/20/2009 10:34:15 AM EST
Originally Posted By blindman45:
Originally Posted By MikefromTX:
Originally Posted By DasRonin:
Pull the bolt carrier group. Place a cartridge against the bolt. If the 5.56/223 is smaller than the recess in the bolt face... it probably is a 6.8.



Yeah, I did that and it's 5.56 sized. Liek I said, I don't what a 6.8 cartridge even looks like, but I'm sure the dimensions of the case are different.

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left 6.8SPC, right .223
http://www.chiefaj.com/223_6.8_W_TEXT.jpg


Based on that picture , a 5.56 wouldn't even chamber in a 6.8 rifle, since the case neck is farther forward than a 6.8's.

That being the case, I'm safe, since a 5.56 round seats flush in the chamber.

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Link Posted: 9/20/2009 10:37:37 AM EST
Does this dealer fly a blue banner at the show
Link Posted: 9/20/2009 12:08:20 PM EST
[Last Edit: 9/20/2009 12:09:26 PM EST by MikefromTX]
Originally Posted By sweatpants:
Does this dealer fly a blue banner at the show


Nothing secret about it - it's Texas Star - they also have a company called Lone Star Wholesale. They're usually the very first set of tables at the 11:00 corner of Will Rogers if you consider you enter the hall at 12:00. Stacks of Rock Rivers and cases full of lowers, uppers, parts and accessories. Located in The Colony. Good people.

You'll also find them at Mesquite and Dallas shows and I think they also make the shows in Houston and other places.

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