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6.8SPC Upper


Zak Smith

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The Fedex man just dropped off my 6.8SPC upper. MSTN built this for

me and Wes has been great.

Modified Bolt:

117_1732_img.jpg [ link to larger image ]

117_1736_img.jpg [ link to larger image ]

Troy sights:

117_1742_img.jpg [ link to larger image ]

It is, really:

117_1746_img.jpg [ link to larger image ]

117_1749_img.jpg [ link to larger image ]

117_1753_img.jpg [ link to larger image ]

Full index: http://apollo.demigod.org/~zak/DigiCam/6.8mm/

Details: 18" stainless barrel, chambered by PRI. OPSINC 4-port brake

K-G coated black. Handguard is PRI. I believe the upper receiver is

LMT. Bolt is custom machined. Bolt carrier is JP.

-z

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Got out today and had time to shoot about 20 rounds. Recoil is comparable to 5.56. The gun ran perfectly. 5.56 mags do not work well, holding only 5-8 rounds. A replacement mag body plan is in the works.

The ammo I have is pre-production, which I bought as a source for once-fired brass. Because of the prototypical nature of that ammo batch, it is not accurate. Handloads using the 110gr VMAX or 115gr Hornady should be sub MOA easy. Powders of comparable speed to 2230 are reputed to work well.

My custom dies should arrive in about 2-3 weeks.

-z

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You said the 5.56 mags only hold 5-8? Do they single stack in the mag? They don't look much larger in dia. than the 223.

I haven't been following the rifle major threads so if its been covered forgive me,

does it make major?

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No, they do not go single stack. The 6.8 rounds are wider towards the shoulder than the 5.56 rounds. 5.56 mags have deeper ribs on the forward end, and I think this conflicts with the wider shoulder. After about 6-8 rounds, it gets hard to seat the next on in the mag.

Yes, 115gr bullets make major (320PF) , but barely. 120gr bullets with a short ogive would be easier to make major with.

-z

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Get thee to a chronograph and report post haste.

Try Thermolds. They are supposed to work better for larger rounds.

Even if 6.8 does make new Major, nobody is going to use with only 8 round mag capacity. It'll take a long time for any special military magazines to trickle down to us peons.

How about 7.62x39 mags?

Edited by Erik Warren
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No-go on the Thermolds. I tried Orlites, USGI 30's, and Colt 20's.

Even if 6.8 does make new Major, nobody is going to use with only 8 round mag capacity. It'll take a long time for any special military magazines to trickle down to us peons.

Cynical grouchiness aside...

PRI will be releasing replacement mag bodies for 5.56 that just happen to work very well holding 28 rounds of 6.8. http://www.ar15.com/forums/topic.html?b=3&...t=184872&page=1

Just like you buy mag conversion kits from Armalite for your AR10, or replacement mag bodies for your S_I, so will this deal work.

Enjoy.

-z

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EricW,

The stock is the Magpul M93A made by Magpul http://www.magpul.com It's a telescoping stock that is rock-solid and has better features than the regular CAR-type telestocks. It can be had special-order in a post-ban compliant version - you pick what length you want it fixed at.

Rich, the owner of Magpul, is just down the highway from me. He builds good stuff and is a good guy to do business with.

-z

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For those who want to know, Model 1 Sales (love em or hate em) has compete 6.8 uppers for $440 including bolt for a 20" 1-9.5, they also have 24" SS bull barrels for $265 with the gas block.

I was told they have all the parts ready they are only waiting for commercially available ammo to release them, should be Early next month.

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  • 2 weeks later...
Hey Zak, what do those Troy sights and that handguard run? What gas block are you running underneath?

The Troy sights are $120m each for front and rear. The rear only has the large aperture. The handguard is the GenIII from PRI, which goes for around $320. The gas block is a stainless low-profile from PRI, about $50. Looks just like this but in ss:

FHWFO-mk12m1c.JPG

Do you have to remove it to attach pieces of rail, or are the holes threaded so you can just bolt stuff on there when you feel like it?

The holes are not threaded. They use a "backer" similar to how the JP rails connect to the JP handguard. The ones in front are possible to remove and replace without removing the tube, the rear ones probably not. The barrel nut does not have to be removed to remove the tube - it connects just like an Armalite float tube.

-z

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  • 1 month later...

6.8SPC FAQ: http://apollo.demigod.org/~zak/firearms/6.8SPC/faq.php

The upper runs fine. I've got a set of dies form the Hornady custom shop, and about 400 rounds, so I'm experimenting with load data at this time.

The "new" manufacture Remington ammo is supposedly quite accurate - 8" @ 600 yards. I only have some of the old preproduction stuff (not accurate due to powder contamination) and my handloads. N135 is real accurate, but not fast.

-z

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Dude,

You rule on response time!

When you get the load worked out, you'll have to let us know how the gun runs under rapid fire conditions (i.e. 3-Gun type scenario).

Any trouble making major PF? What's your barrel twist?

Oh, do you have a website for MSTN or PRI?

Thanks,

Rich

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