A question about the 6x6.8 SPC

hcb

New member
Hey, All. I have a 6.5 Grendel I've used for years for hunting hogs, coyotes, and bobcats. As I'm running out of bullets (less than 100 left) and as Nosler hasn't made any of those bullets so far this year (per a call to them), I'm looking for an alternative cartridge.

The 6mm ARC has press talking about heavier bullets like 103gr and up, but I want to shoot 90-95gr bullets to achieve higher MV. I read somewhere that the 6x6.8 SPC is better for lighter bullets. I presume the "better" is having greater case water capacity because the shoulder is farther forward. Having the shoulder farther forward would reduce the length (weight) of the bullets which could be seated or some such. More powder, less bullet. Regardless, I want a cartridge for a 6mm projectile for an AR-15 which will allow maximum powder/velocity for 90-95gr bullets. Specifically, I have Hornady 90gr ELD-X and Nosler 95gr BT. Obviously there are safety concerns, I can't just pour gobs of any powder behind the bullet, but first is to find *which* 6mm AR-15 cartridge, then it will be time to look for load data.

I'm having a hard time locating any information to support that the 6x6.8 SPC would be any better for 90-95gr bullets than any other 6mm AR-15 cartridge. I don't think the 6x45 (6x223R) has enough cartridge capacity for powder to push these bullets to the MV I'm looking for (safely...I could pack it full of Titewad...no...just no). For comparison, I push 100gr Nosler BT out of a 16" Grendel barrel at 2,750 FPS.

Thanks for any information.

--HC
 
Have you thought about the 100 gr amax or 95 gr vmax in you Grendel?

Otherwise, the Arc would do fine with 90's, take a hard look at the 87 gr vmax, great bullet imo. That's on the upper end of what would be comfortable in the 6x6.8, most shoot the 58's and 70's out of it.
 
If I was gonna shoot 90's I would probably just stick with the 6.8 spc. As far as dropping down in bore size to the 6x6.8 I would concentrate on 70 ish grain bullets. The 25dti is another option but I'm not sure on 25 cal bullet availability. Barrel length is gonna play into the equation as well.
 
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You can get the 87-90's in the 2850-2950 range in the 6ARC... and that's an 18"barrel. Not sure about the 6x6.8, I don't have experience with that.

I have an ARC and I do love it. My only gripe about it is the fat case head when getting on to a coyote stand. With the case head so fat, the extractor does not easily get over the rim. It cycles flawlessly but I can not pull the charging handle and slowly (quietly) load one into the chamber. Even with the forward assist. The bolt wont seat over the rim. I have to pull the handle and let er drop. The action on an AR15 is about 117 db. My .223 ar easily will load a round when slowly closing the bolt.

Not a huge con, but I'd prefer if weren't that way. I guess you running a Grendel already you probably notice this too... or is it just my rifle?
 
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Originally Posted By: Kpuck08You can get the 87-90's in the 2850-2950 range in the 6ARC... and that's an 18"barrel. Not sure about the 6x6.8, I don't have experience with that.

I have an ARC and I do love it. My only gripe about it is the fat case head when getting on to a coyote stand. With the case head so fat, the extractor does not easily get over the rim. It cycles flawlessly but I can not pull the charging handle and slowly (quietly) load one into the chamber. Even with the forward assist. The bolt wont seat over the rim. I have to pull the handle and let er drop. The action on an AR15 is about 117 db. My .223 ar easily will load a round when slowly closing the bolt.

Not a huge con, but I'd prefer if weren't that way. I guess you running a Grendel already you probably notice this too... or is it just my rifle?

Probably your extractor, you might try very slightly beveling the corners, and polish the front beveled part, I think it's called "dehorning" the extractor.
 
I took it to my gunsmith, he did just that and it didn’t seem to make much of a difference at all. I noticed the extractor doesn’t have as much range of motion as my .223 bolt. So I just chalked it up to the fat case head. Maybe I should just try a new bolt all together… I hear it’s a good idea to have a spare with these Arc’s.

I looked at the 6x6.8 quite a bit before I got the Arc… factory ammo is a nice option to have. I built this just for coyotes and had the 87 Vmax in mind. The broken bolt with higher pressures worried me a bit but I had a few cold ones on my birthday and Midway USA had 10% off for a b day purchase… saw a Proof carbon fiber 6arc and just decided to send it. I’m happy with it but I do think the 6x6.8 might be better for the 70-90 gr class.
 
Out of curiosity do you have the bumper on the extractor spring on your bolt? If so try it without it. I run over a dozen Grendel/6.8 variants and none of them use it. That's the first thing I remove on a new bolt. If you go to ARFCOM you can find polishing pics for the Grendel bolt done bt a guy named Big Bore.

Greg
 
Originally Posted By: 204 ARHave you thought about the 100 gr amax or 95 gr vmax in you Grendel?

Otherwise, the Arc would do fine with 90's, take a hard look at the 87 gr vmax, great bullet imo. That's on the upper end of what would be comfortable in the 6x6.8, most shoot the 58's and 70's out of it.

My apologies for not replying sooner to all: re-opening Edge didn't refresh the page so I thought I had no responses.

No, I had not considered the Amax. To be honest, I didn't know they made those (100gr 6.5 Amax). I will check the cost and availability of them.

Maybe I'm drinking too much of the Hornady Kool-Aid but I thought they promoted the Vmax as more of a varmint bullet which, in practical application, I would expect to have a thinner jacket and, presumably, reduced penetration. I bounced a 2,750 FPS 100 GR ELD off the cartilage cape on a hog a few years ago and that experience is stuck in my head. That keeps "penetration" in my head. It knocked him unconscious for about a minute or 2 while I was patting myself on the back for the hit and thanking God for the answer to prayer that one showed up to test out my new Grendel. While I was walking over to take a pic he jumped up and started to run off. He didn't survive the next shot...but...penetration. It had a very nice, white hiway where the bullet skinned his cape across his neck/shoulder area.

I'll see what I can find for load data for the 6x6.8 for the 90gr bullets. I have some 90gr ELD-X already.

I broke out my 6mm Predator barrel in the last few days. I shot some test loads about 4 years ago when I got it and put it up when I found a load that worked well in my Grendel. I'll make a reply to my post regarding what I found.

Thank you for your reply.

--HC
 
Originally Posted By: varminter .223If I was gonna shoot 90's I would probably just stick with the 6.8 spc. As far as dropping down in bore size to the 6x6.8 I would concentrate on 70 ish grain bullets. The 25dti is another option but I'm not sure on 25 cal bullet availability. Barrel length is gonna play into the equation as well.

A quick check of the Nosler and Hornady sites only reveals a 100gr from Hornady in a solid copper and Nosler in a an Accubond, for the 6.8 caliber. I've tried solid copper bullets in a 224 Valkyrie hunting pigs and...no. Nope. High velocity around 3k FPS and close range and just poked holes in them and not terribly lethal. And the Accubond is a bit pricey at an MSRP of $1+ each.

I'll look at the 25 cal stuff, but I like the 6mm caliber because of the wide range of bullets manufactured and their availability.

Thank you for your reply.

--HC
 
Originally Posted By: Kpuck08You can get the 87-90's in the 2850-2950 range in the 6ARC... and that's an 18"barrel. Not sure about the 6x6.8, I don't have experience with that.

I have an ARC and I do love it. My only gripe about it is the fat case head when getting on to a coyote stand. With the case head so fat, the extractor does not easily get over the rim. It cycles flawlessly but I can not pull the charging handle and slowly (quietly) load one into the chamber. Even with the forward assist. The bolt wont seat over the rim. I have to pull the handle and let er drop. The action on an AR15 is about 117 db. My .223 ar easily will load a round when slowly closing the bolt.

Not a huge con, but I'd prefer if weren't that way. I guess you running a Grendel already you probably notice this too... or is it just my rifle?

I don't know about the 6mm projectiles but the larger diameter stuff like the 308 doesn't change much in MV from 18 to 16 or 20. The smaller stuff like 224 seems to vary more. Obviously, I'd expect the 6mm/243 to change more like the 224. 2,850 dropping 100 FPS in those 2 inches would be perfect (I want a pony, too). I did ballistics calcs on the 6.5 100gr Nosler BT at 2,750 FPS versus the 6mm 90gr ELD-X at the same MV and it's almost identical up to 400 yards with the slightly higher BC of the ELD-X. I don't shoot past 300 often and 400 is a hail Mary for me with thermal. Okay, all my shooting is hail Mary's...fine.
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I have a 6mm ARC reamer but not the time to cut a barrel with it. I'd buy a barrel just to play with it if Ballistics Advantage made one with the heavy flutes.

I did not have a problem soft-closing my bolt that I noticed on my old upper. I bought some fancy, low-weight receivers (upper and lower) and the upper doesn't have the FA to save weight so I always let it fall hard and have for 3+ years I've run this rig. But, after a few times in the past when I thought the bolt was fully locked and it clicked instead of a bang...I'm a fan of the full blow always. I, too, have done the soft close when in close proximity of whatever I was hunting and it's handy...but it lead to a few clicks...and startled, running prey.

Thanks for your reply.
 
Originally Posted By: DiRTY DOGBrass quality and availability should be a consideration.

I agree and those are good points. Thank you.

--HC
 
Originally Posted By: Kpuck08I took it to my gunsmith, he did just that and it didn’t seem to make much of a difference at all. I noticed the extractor doesn’t have as much range of motion as my .223 bolt. So I just chalked it up to the fat case head. Maybe I should just try a new bolt all together… I hear it’s a good idea to have a spare with these Arc’s.

I looked at the 6x6.8 quite a bit before I got the Arc… factory ammo is a nice option to have. I built this just for coyotes and had the 87 Vmax in mind. The broken bolt with higher pressures worried me a bit but I had a few cold ones on my birthday and Midway USA had 10% off for a b day purchase… saw a Proof carbon fiber 6arc and just decided to send it. I’m happy with it but I do think the 6x6.8 might be better for the 70-90 gr class.

I use the JP bolts which many swear by. I'm a hunter, not a real gun nut and I don't take great care of my stuff: I hunt, shoot some, put it back in the back seat until next time. When it starts to feel gritty, I clean it by taking it apart and hosing it down with brake parts cleaner, oiling it, and then I put it back together. The point here is my rifle is not a safe queen at all. I'm also pushing 100gr bullets at 2,750 FPS which I think is a bit hot. I don't count rounds, either, but I think I got about 1,500 rounds out of my first bolt before I knocked a lug off it. Maybe more. Yes, a spare bolt is light and easy to carry, carry one. But, factory ammo or "not-aggressive" loads and better care and I believe you'll be good for a very long time if not indefinitely.

--HC
 
I love the 6.8 SPC II using 120 SST and 90 GD's.

In short, I agree with most of what has already been said.

 
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I have 2 Grendel's,1 6ARC, 1 6.8 SPC and 1 6x6.8. Honestly the Grendel's and ARC stay in the safe. I broke 2 lugs trying to get more speed in the grendel so it makes me nervous hunting with them. I get on average 100 fps faster in a 6x6.8 up to about 95 gr. That's the heaviest I've shot with it. Not all bullets are that much faster but that's about what it averaged out of 20" tubes. They are loaded kind of hot though.
If it were me I would throw together a 6.8 SPC to hunt hogs but I do know you have more options in 6 mm.
 
I pulled the rubber o-ring off the extractor spring last week... it will now easily lock the lugs when slowly closing the bolt. Still need the forward assist, but just an easy push. Cycled just fine on the 6 shots I sent at a running dog the other day... dogs is still running!
 
Originally Posted By: Kpuck08I pulled the rubber o-ring off the extractor spring last week... it will now easily lock the lugs when slowly closing the bolt. Still need the forward assist, but just an easy push. Cycled just fine on the 6 shots I sent at a running dog the other day... dogs is still running!

The first thing I do with a new bolt is throw out that o-ring. Also polishing the extractor is a plus if you have a few minutes to invest. Much smoother running IMHO. The later us really helpful on Grendel based cartridges.

Greg
 
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If I was gonna shoot 90's I would probably just stick with the 6.8 spc. As far as dropping down in bore size to the 6x6.8 I would concentrate on 70 ish grain bullets. The 25dti is another option but I'm not sure on 25 cal bullet availability. Barrel length is gonna play into the equation as well.
Trouble is there are only 2 90 gr bullets to choose from. Neither are ever available and aren’t great varmint bullets at 6.8 velocities.
The 6.8 is a nice hog round with the 120SST.
The 6.8 spc II is gonna die in my opinion because nobody stepped up and designed bullets for it.
Im likely to replace mine with a 6 arc for coyotes and hogs.
 
Not to hijack your thread but who is building quality 6x6.8 or 6 WOA barrels? I'm in the market but I'm striking out so far on who can build one.
 
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