6mm SPC??? Is it worthwhile?

[mleeber]

I have a few LWRC Six-8 SPC matched upper/lower receivers and I am trying to figure out what to do with them. I have tried 224V and 6ARC but the LWRC/Magpul magazines dont like the the ARC or Valkyrie rounds, the mags get fat and will not easily go in or out of the magwell. So now I am looking at using the 6.8 for a wildcat. And yes, I have spent weeks redesigning followers and that did not help, the 6.8 SPC is a tapered case and the other are not so it would take a complete mag redesign I suspect.

My real question is: Is the 6 SPC as inherintly accurate as the 6ARC and 6 Dasher? Is brass available or do I have to use 6.8 SPC brass? And who makes a good barrel in 6 SPC? I will be shooting this at long distances in DMR matches and such.

Thank you!

 

[Shurefire]

As far as the mags go, there are plenty of options for 6.8spc, so no need to redesign the mags.

 

[mleeber]

The mags in an LWRC are custom jobbers done for them by Magpul. They are fatter and a little longer which is why I used the LWRC for 224V and 6ARC to get the mag capacity and a little bit more OAL. The LWRC Six-8 lower is not a milspec lower.

 

[Clancy]

I shot a 6 WOA, which is about as close as you can get, for 8 seasons in a bolt gun. It shot very well with 65 and 70 grain bullets, and of there were better brass available, I’d do it again- but there’s not.

I think Lapua will make 6 ARC in the future, so you’ve got that to look forward to.

 

[Fast14riot]

240 Tomahawk, 6WOA, 6GPC are all variants on the same theme. However, going to 6.5mm on the 6.8spc case has proven to be much less hassle and more accurate. I'm slowly working on a 30cal version, for a rimless 30-30 BR cartridge. Case capacity is just about perfect for a 300 yard gun. Only problem is bolt face diameter. Either need to open up a 223 or find a gun sold as a 224 Valkyrie.

 

[Fast14riot]

I shot a 6 WOA, which is about as close as you can get, for 8 seasons in a bolt gun. It shot very well with 65 and 70 grain bullets, and of there were better brass available, I’d do it again- but there’s not.

I think Lapua will make 6 ARC in the future, so you’ve got that to look forward to.

If you can get S&B 6,8 spc brass (notice the comma) or Hornady 6,8 spc brass made by S&B (again, notice the comma) those are the best quality 6.8 cases out there. I've shot the 6.8spcII for over 10 years in silhouette and steel matches, using lathe turned solids, to speer gold dots. I know the cartridge and case well.

 

[Knotwild]

Dedicated Technologies (D-Tech) has been chambering it for years. 30 degree shoulder. He says 3K with 85gr.

6 DTI

 

[SteveOak]

Is the 6mm SPC a 6mm BR deriviative?

 

[CJ6]

Different size case (smaller diameter). 6.8 spc

 

[Knotwild]

Is the 6mm SPC a 6mm BR deriviative?

No. It's the Remington 6.8 SPC necked to 6mm. The DTI blows the shoulder forward to 30 degrees. The case is rumored to be based on the 30 Remington. In the case of the 6.8 SPC, it was created to address weakening the bolt face in AR's when the bolt face is opened up for cases using larger diameter bases. The 30 Remington has a case head that is 0.421 in diameter vs. 0.473 for the 6mm BR, and 0.376 for .223/5.56.

I don't own one, but i gathered all this because I was considering a DTI 6mm once.

 

[Fast14riot]

6.8spc is based on the parent case of 30 Remington. It was developed specifically for performance in short (carbine length) barrels with effective terminal performance. The case head size of 0.421 worked out to create a stronger bolt than Grendel/PPC/X39 .440". In the early days of the Grendel, there were blown apart bolts, then the Grendel 2 chamber and bolt design came about to fix it, but the 6.8 as designed also had it problems.

As developed, it was great, but Remington when submitting the print to SAAMI got the cone angle incorrect at the end of the chamber and had a much shorter freebore. This is what lead to the 6.8spcII. Pressure issues were common with the spc chamber, which also explains why you can run quite a bit hotter in a spcII chamber than an original SAAMI chamber. I'm not aware of any manufacturer producing a SAAMI spec chamber for an AR15 barrel currently.

However, there have been some very accurate chamberings on this case. Bullets from 100-120 grains in calibers 6.5 or larger seem to be the real accurate ones. 6mm in various chambers has been so-so, haven't seen anything really precise yet.

 

[SteveOak]

I appreciate the replies but the question was rhetorical.

 

[30378]

I have a 6mm SPC in a gas gun with a 20" bbl. It does it's best with IMR8208. Shoots about 3/4MOA with 95gr Nosler Ballistic Tips at 2800fps. Don't think I would build another as I also have a 6mm Grendel (not an ARC) with a Saturn bbl that is unbelievably accurate for a gas gun.

 

[danny]

I have a few LWRC Six-8 SPC matched upper/lower receivers and I am trying to figure out what to do with them. I have tried 224V and 6ARC but the LWRC/Magpul magazines dont like the the ARC or Valkyrie rounds, the mags get fat and will not easily go in or out of the magwell. So now I am looking at using the 6.8 for a wildcat. And yes, I have spent weeks redesigning followers and that did not help, the 6.8 SPC is a tapered case and the other are not so it would take a complete mag redesign I suspect.

My real question is: Is the 6 SPC as inherintly accurate as the 6ARC and 6 Dasher? Is brass available or do I have to use 6.8 SPC brass? And who makes a good barrel in 6 SPC? I will be shooting this at long distances in DMR matches and such.

Thank you!

I think that you are .5 too low. It is a known fact from the fanboys that you have to dump everything and be into 6.5.

Danny

 

[usmc 0311 rvn 67-68]

I have a 6SPC and a 6SPC Imp in a howa Mini and 1500. The mini with a 25" barrel will push a 75 grain V-max to 3200 fps and is quite accurate at that velocity. The Imp. likes Sierra 80 gr. Blitz @ around 3050 fps. Both have 1 in 8 twist Kreiger barrels.

 

[Panzer22]

if you have the SIx8 receivers why not a 6 Hagar?

 

[Fast14riot]

if you have the SIx8 receivers why not a 6 Hagar?

Haven't looked in a long time, is Hagar brass available these days?

 

[Panzer22]

it comes up occasionally. I neck it to 22 for a 220 Thunderbolt. I wanted to build a 220 on the Six8 set up years ago. Best I can remember, it would have been a great fit.

 

[VA_XTC_Shooter]

240 Tomahawk, 6WOA, 6GPC are all variants on the same theme. However, going to 6.5mm on the 6.8spc case has proven to be much less hassle and more accurate. I'm slowly working on a 30cal version, for a rimless 30-30 BR cartridge. Case capacity is just about perfect for a 300 yard gun. Only problem is bolt face diameter. Either need to open up a 223 or find a gun sold as a 224 Valkyrie.

Can you share more about the 6.5 necked down 6.8? Same shoulder angle? What bullets can you run mag length? I like the 240 Tomahawk for being able to run 105s mag length if desired, but am thinking a 6.5 would be a better option.

 

[Fast14riot]

Can you share more about the 6.5 necked down 6.8? Same shoulder angle? What bullets can you run mag length? I like the 240 Tomahawk for being able to run 105s mag length if desired, but am thinking a 6.5 would be a better option.

Yep, pretty much just a bushing change. Ballistically it mirrors the Grendel, so unless you can do it yourself and already have brass/bolt it may not be financially viable.