6.8 SPC - owners / users chime in

DJL2

Hurricane 6
Oct 16, 2013
86
37
18
Center of the Military Universe
#51
The margin for error is just smaller for the "big bolt" version of the -15. It's a system designed around a certain caliber, bolt, bolt face, bolt lugs, etc. There was a safety factor in that design that has proven generally adequate for the 5.56. It is usually adequate for the 6.8 and 6.5 - however, when you build a rifle from parts, there is always a risk of tolerance stacking. The original design is relatively forgiving of this, the 6.8/6.5 much less so. Of course, plenty of guys building 5.56 -15s have had no end of troubles trying to do a budget mix-n-match build.

The whole system can be ammo sensitive as well, something that AGBs can help with. Examples:
My issue M4 back in 2005-2007 - ran A-OK w/ M855, did not run acceptably with UK SS109. M16A4s ran the UK SS109 just fine.

My current 6.8 SPC - runs so well you could hold out your hand and catch brass without moving it IF you feed it full power loads; feed it under powered / light loaded budget ammo and you'll be running the bolt by hand at least a few times a magazine.

My current 6.5 G - over gassed to the point that it doesn't just run, it beats the case mouth in on ejection; feed it WPA and be prepared to cycle by hand.

My 5.56 SBR - full power ammo is one setting on the AGB, cheap/light ammo (e.g. UMC - I generally regard this as garbage, but will shoot it if someone else is buying it) needs a different port setting. My DDM4V1 will run garbage ammo or great ammo, doesn't care. Gas port size and dwell time are a couple of concepts to acquaint yourself with.

I said no dissertation...I'm trying...
 
#56
My father and I have done the 6.8 SPC dance a few times now. Getting a quality barrel (e.g. correct gas port size, accurate) is important. Getting the action spring and buffer matched to manage how it runs, super important. Basic stuff, I know - but, getting it wrong will abuse brass and your rifle. My Dad is running JP bolts and a coated carrier at this point, having broken several. His range bag includes spare bolts, extractors, and other small arms repair parts. He's not a "match" grade shooter, but he does put a lot of rounds down range banging steel and bagging an occasional piggy.

My 6.8 is relatively new - haven't finished gathering chrono data. Mostly got it to help work up loads for my Dad, honestly (don't need to be match accurate, just safe). I have a 16 inch Bison barrel on it, mostly for reasons of economy. I've been meaning to get it dialed in for the 120 grain SST...I just shot part of a box a couple weeks back with an SD of 6 fps and want to know what it will do. I threw on old school Trijicon Accupoint on it (the 1.25-4x variety), but need a better mount. The 120 clocked around 2450 fps for me. Of course, I could always just load 90 grain and go ham ;-).
Your dad has broken several JP bolts? I've been on 68 forums since June 2007 and there have only been 3-4 reported broken bolts in all of that time and 2 were due to overcharges, pistol powder in one of them.
 

Primus

Gunny Sergeant
Feb 13, 2017
835
331
63
Vancouver, WA
#57
Not inside 300 yds where most game is shot. Hornady 6.8 ammo starts off 100fps faster than the Grendel out of the same length barrel. 400Bc VS 464 BC isn't that big of a difference. If I was shooting paper I may go with a Grendel but if hunting the 6.8 performs better.
And u can load one or the other hotter. Look at muzzle energy to get a better comparison. See which one bleeds energy faster.
 
#58
What does 6.8 offer over 6.5g? Waiting......
Better terminal performance at ranges game is shot at. Bigger bullet going faster =better terminal performance. Do you Grendel guys really shoot deer at 500yds with a Grendel? What velocity is your bullet going at 500yds? Does your bullet expand at 500 yds ? Yeah I have heard that LRRPFFFT guy yak about better SDs...What is the SD of a 6.5 one instant after it contacts anything? Can't answer that can you? So does SD really mean it penetrates better? NOPE.
 
#59
And u can load one or the other hotter. Look at muzzle energy to get a better comparison. See which one bleeds energy faster.
Yeah I can load a 6.8 a lot faster than a Grendel. I made an offer on AR15.com years ago to the guys that run the Grendel forum. If you want to race I'll race. Bring the baddest Grendel you can find and I'll bring a 6.8 and I'll smoke that Grendel. Use the same weight bullet and the same length barrel. Back in 2008 when we were pushing the 6.8 for military adoption we were shooting 115gr bullets at 2800fps out of a 16" barrel. Try that with a Grendel and let me know if you want to race. Let me know what town you live in and I'll find a customer that will meet you at the range.
 
#61
You seem to emotionally invested to have an intelligent conversation about it.

6.5G won...by a mile and for good reason.
Seems you are the one that can't answer the questions. Any time you want to race just let me know. I sell both 6.8 and Grendel barrels and can use either. For hunting I'll use the 6.8 because I have seen the difference starting around 2005.
This is what happens when you try to push a Grendel...notice the cases and how they look like a belted magnum? Almost ruptured the cases. grendel belted.jpg
 
#62
Difference between 6.8 and Grendel cases. Notice how much case capacity that 123gr bullet takes out of the Grendel case? Look low inside the Grendel case in the lower corners. See how thin the case walls are? That is why Grendel cases can't handle pressure well. On top of that Bill Alexander decided to use a .136 recess bolt face. That pulls the case .012" further out of the chamber making .012" more unsupported by the chamber walls. The thin walls of the case can not handle 52000psi UNLESS it is supported by the chamber. 6.8 vs 6.5.jpg The photo of the Grendel cases in the post above is the result of thin unsupported case walls and 58000psi. The 6.8 can handle 60,000psi easy without swelling or breaking bolts.
 
#65
What is your financial stake in the 6.8? LOL I can show u pictures of all flavors of broken bolts, short of KAC E3.
Honestly it's just you Grendel guys jumpming into every 6.8 thread on the internet. You guys have been doing it since 2006 starting with John Hanka, owner of the Grendel forum and his right hand man Bill Waites. Everyone deserves to hear the other side and the truth instead of just opinions from a bunch of fanboys. Now show us some photos of broken 6.8 bolts.
 
#67
What is your financial stake in the 6.8? LOL I can show u pictures of all flavors of broken bolts, short of KAC E3.
Read this long pile of Horseshit written by LRRPFFFT(the super mod of the Grendel forum)- If you can't see the lies in this I'll bet you're a democrat.
"
burninglegs
01-03-2017, 12:43 PM
Here is a history lesson from "LRRPF52" who is a member at AR15.com and 6.5 Grendel.com forums.


The 6.8 and 6.5 Grendel entered the market at the same time.

One was falsely advertised as Special Forces' new cartridge, soon to replace 5.56, right as the gears of the industry were firing up to answer demand for the GWOT, new DHS contracts, and a lot of activity in the defense and firearms world. That advertising caught on, and a lot of people were sucked into it before knowing anything really about the 6.8 SPC.

6.8 was banned from use many years ago, with threats of Court Martial if anyone was caught with it after the ban. The very few people that were testing them on a limited basis, even on deployment, were ordered to turn in their uppers, mags, and ammo, and if a single 6.8 SPC component was discovered in anyone's possession, they would be prosecuted to the fullest extent under UCMJ.

Word is that several people advocating it ticked off the wrong people too many times, several uppers blew up, and when JSOC tested it, they determined it to be unsafe for use. There were guys involved with it that literally had to be escorted off of Fort Bragg after being told to go away by several units within the Special Operations community.

On the civilian side, the proponents managed to make an impression with the DOJ head ballistics lab, who said as long as he worked there, he would never sign off on 6.8 for domestic LE use, since deception was used to represent the terminal performance of the cartridge by substituting varmint projectiles for Open-Tipped Match, in an attempt to dovetail that over to the military side for the sign-off on OTM use by JAG. As soon as they were rejected by the Fed's Ballistics Lab, they went to the UK and told the Ministry of Defense that they had better start tooling up now or get left behind, because this was going to be the new 6.8x43 NATO service rifle cartridge.

Remington's involvement with the cartridge was nothing short of a colossal abortion of epic magnitude. Of all the ammunition manufacturers one could go to, they went to big green box. Ask anyone who owns 6.8 how they feel about Remington's involvement with the cartridge.

It could have been a really nice little cartridge in .257, which D-TECH does as the 25 DTI, but the combined competence of the people involved with developing the 6.8 purposely chose to ignore the optimal caliber studies that had already been done by the Army on at least 2 different occasions, to include the pig studies. They chose the larger bore of the .277 instead for some reason, even with a case length of 43mm inside the AR15s very tight 2.260" COL.

SF and other units within USASOC went with the Mk. 262 77gr 5.56 Match load in accurized rifles instead of switching to a new cartridge. SF later tested and fielded the 70gr Barnes TSX load with brown-colored tips, with devastating performance on human targets.

The Army has since gone to M855A1, which has better armor defeat capabilities than M855, with terminal performance on tissue that is quite impressive.

The Marines went to the Mk.318 Federal SOST cartridge.
http://www.65grendel.com/forum/showthread.php?13105-Not-trying-to-start-a-fight..../page2



This photo is from one of the proponents. Notice anything?
http://www.itstactical.com/wp-content/uploads/2009/07/pic9.jpg


The reason they picked the 6.8 SPC (0.277 projectile) was because the ballistician Dr. Gary K. Roberts, stated that the caliber supposedly performed the best in his gel tests. However, that is debatable as each projectile in his tests weren't comparable on an comparable basis. His 6.8 SPC was a modified Hornady V-Max that expanded impressive while the competition were inferior rounds like the 6.5 using the 120 SMK which was doomed to fail because it barely fit in the case mag length. Lots of trickery and manipulation was done to get the 6.8 SPC to the top."
 
#68
If you read the post on the internet all of the Grendel guys say the Grendel beats the 6.8 by a mile. Since 2006 I've been saying they are much closer than the G crowd likes to admit when using fair data of bullet and barrel length and not comparing a 16" 6.8 to a 24" Grendel. Using Hornady factory ammo data in equal length barrels 123SST VS 120SST the 6.8 120 starts off apx 80fps faster. Handloads could put another 100 fps between the 2 but this is a comparison of factory ammo performance. Using Jbm software and the true BCs of both bullets not the inflated BCs posted by Hornady this is the result. At 100 yds the 6.8 has around 40fps more energy. 200 and 300 are near the same, at 400 yds the Grendel has apx 40-50lbs more energy. Ok so if the Grendel slaughters the 6.8 at 400 because of 40ftlbs the 6.8 Slaughters the Grendel at 100yds because of the same 40ftlbs. I wouldn't call 40lbs of difference in energy a "slaughter" but the Grendel crowd likes to say that. IMO opinion being the key word, the 6.8 and Grendel are very close in performance out to 400yds and by the time both bullets get to 500yds the velocity is below the expansion threshold so the bullets may not expand. I would not use a Grendel or 6.8 to shoot game past 400yds and most game is probably taken under 150.
Personally I don't use "energy" as the defining factor of performance. I look at the actual performance of the bullet on game. I want a bullet that expands, retains weight and does as much damage as possible without fragmenting. That ensures good penetration. If the bullet passes through the animal all energy is not transferred to the animal so the energy number may not mean anything. Actual bullet performance on game is the only thing that matters and you can't figure that using the "BC"
The G crowd loves to say the SD(sectional Density) of the 6.5 bullets is higher so they will penetrate better. Total BS. As soon as a bullet strikes anything the SD numbers are out the window. The bullets frag, deform or tumble and there is no way possible to figure the SD. SD was used back in the 1800s before anyone could calculate BC. They determined the Mini ball would travel flatter because the shape allowed more weight with less frontal area. Bullets with a high SD would fly flatter and be more accurate. These days "SD" is a useless spec because the BC defines everything related to exterior ballistics.
To end this OP don't concern yourself with what people you don't know say on the internet. The 6.8 is a fine choice and will perform well if you choose the right bullet for the job. I think the 6.8 has a better selection of hunting type bullets. Many like the 120sst, it is kind of explosive and drops hogs quick, may damage too much meat on deer if hit in the wrong spot. Cavity back bullets, Barnes and Accubonds are premium bullets, they hold together well and are good choice for deer and hogs IMO. The Fusion bullets seem to be picking up fans and reports are good. If you want to shoot longer range the 130 Berger Classic Hunter is a good choice.
 
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Niles Coyote

Gunny Sergeant
Aug 13, 2007
3,999
372
83
South West, MI
#74
I have my 6.8 upper together!

With a BCM receiver, MI CMR 12.65" handguard, an older syrac adjustable gas block, SLR's single port brake and my m-16 bcg this weighs in right at 4 pounds on my kitchen scale.

Ammo is loaded for testing, starline brass, cci #41 primers, 110 hornady bthp using imr8208 from 29.6-30.6 in steps of 2/10ths. Hope to test this out in the next few days.
 

Baron85

Sergeant
Mar 18, 2012
430
56
28
33
#76
Loving my home built 12.5” ARP barrel 6.8. Just took off my bushnell 1-6.5 and put a vortex 4-16hst on to test accuracy. I have been getting around 1.5” groups at 100yds with factory hornady 120sst. I don’t shoot low mag optics very well so wanted to try the vortex and see what the rifle will really do.
 

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Stooxie

Sergeant of the Hide
Oct 11, 2018
153
91
28
#77
The primary falsehood on which the Grendel fanatics stand is that 6.8 and 6.5 are equal below 400 yards. This is simply not true. For any given barrel length, 6.8 SPC has higher muzzle velocity (100 to 200 fps), higher energy and higher terminal energy. The 6.5 does not "pull away" after 400 yards, it retains more speed once 6.8 slows down enough to match it. That's been proven 1000 times over, despite what any of their tortured logic or apples to oranges comparisons say. Don't even talk about sectional density as it relates to terminal performance. Most of people's thoughts on that are old wive's tales.

Yes, these linguistic details and numbers are important. Under 300 yards, which 99% of all kills are made (really under 200), WHY NOT go with the round that has more energy and a flatter trajectory? A search at any ammo vendor shows far more factory loads for 6.8 SPC than for 6.5 Grendel. Does it really matter? Maybe not, but it's just one more piece of BS that the average sworn Grendel fanatic is going to hit everyone with.

Take away Wolf Steel and 6.8 is actually cheaper to shoot. DEFINITELY cheaper to hunt.
Take away long distance shooting and the Grendel fanatics have nothing left.
Take away hand loading and the bullet selection argument is gone (which is weak anyway, tons of 277 bullets out there)
Keep hand loading and 6.8 can be pushed harder.
Semi-autos don't like short/fat cases. Check out the 65Grendel troubleshooting forum for a fun read.

Whatever, no one aside from the Grendel fanatics gives a rat's fat ass what people shoot. But, fuck, these guys are like a cancer. Once it's there it's damn near impossible to get rid of them and all they do is poison the good stuff around them. Worse than liberals.

The OP asked for 6.8 owners to chime in, not "Hey, can I get some 6.5 fanatics in here to ruin my thread?" Look at the 6.5 threads. Where are the 6.8 fans? Out shooting, not typing on their keyboards.

-Stooxie
 
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Jun 13, 2017
82
18
8
Nashville, TN
#78
I kill a ton of hogs with my 6.8. I’ve made this post a bunch of times but

Bison armory 11.5 6.8 SBR, tbac cb7,night force shv 3-10x42, pri mags and factory hornady 120sst

6.8 is a perfect round for hunting white tail
And hogs in Alabama. I’ve never had a shot
Over 200 yards. I killed 4 hogs point blank range in the deep hard woods the other morning. No jams ever with 6.8, it kills the shit out of Stuff.
 
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Lar135

New Hide Member
Nov 30, 2018
7
5
3
#79
Internet pissing contests aside, I like to match the tool to the job. If I'm hunting anything larger than a coyote at distances beyond 350 yards I'm probably going to pick something other than 6.8spc or 6.5G. I do like my 6.8, I've thought about building a 6.5G but I'm not really sure what niche that would fill for me. I've already got too many rifles that don't get shot enough. :)
 
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Niles Coyote

Gunny Sergeant
Aug 13, 2007
3,999
372
83
South West, MI
#80
I'm using imr8208 and Starline brass with CCI #41 primers. 2/10ths of a grain steps starting at 29.6 at top left and ending at 30.6 bottom right.
20190110_163128-1-1.jpg
The node appears to be 29.9 or 30.0 putting the next node around 30.8 or 30.9... I'll be checking that next time our along with some 120 sst.

5 loaded at 30.0 grains at 300 yards. Minus the shot that drifted I'd have a 1.75" group.
20190110_141954-1.jpg
 
Likes: Lar135
Nov 18, 2011
76
3
8
36
#81
Hey guys, how many of you are using a 6.8 SPC UPPER? What real feedback can you all give me? I am looking to build another upper and will be using it to hunt deer and bang steel some. I was thinking of a 16” or 18” barrel. What say you? Wilson Combat has their barrels on sale, but would like feedback or recommendations on other brands.. Thanks!
57DCA293-07E6-4E96-A080-1154BDBE7E03.jpeg
This is a buck that I took with my Rock River upper. The barrel is from Rock River as well. It’s an 18” barrel with their stupid muzzle device that features teeth for some reason. The lower is an Aero with nice parts I won’t bore you with the list, but it does have a CMC 3.5 lb single stage in it. It’s a sub MOA shooter.

I experienced nothing but problems when I first got the upper. Failure to feed and extract. Long story short the gas port was drilled too small. This is a very common problem with the 6.8 spc. I tried everything before having the port redrilled including an adjustable gas block.

I won’t buy another RR in 6.8 based on my experience. I’d look at the Wilson or an LWRCI.

Hope this helps
 
Nov 18, 2011
76
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#82
I'm using imr8208 and Starline brass with CCI #41 primers. 2/10ths of a grain steps starting at 29.6 at top left and ending at 30.6 bottom right.
View attachment 7001695
The node appears to be 29.9 or 30.0 putting the next node around 30.8 or 30.9... I'll be checking that next time our along with some 120 sst.

5 loaded at 30.0 grains at 300 yards. Minus the shot that drifted I'd have a 1.75" group.
View attachment 7001697
Use Xterminator from Ram Shot with that bullet and your group will tighten up.
 
#84
8208 is a little slow for optimum velocity, we don't hear many people using it. AA2200, 10X, H322 are more commonly used but Xterm, H335, N530 are also used with 100-120gr bullets. 29.5gr RE7 with 90gr TNTs loaded to 2.295 is very accurate for targets and varmints. 28.4gr AA220 with Hornady 110gr HPBT loaded to 2.26 is another one of those loads that is accurate in almost every barrel. The Wilson Combat and Bison barrels use a SPCII chamber and the same 11 twist 4 groove rifling so you may need to load the Hornady 110 and 120 .015-.020 longer than factory.
 
#85
View attachment 7002238
This is a buck that I took with my Rock River upper. The barrel is from Rock River as well. It’s an 18” barrel with their stupid muzzle device that features teeth for some reason. The lower is an Aero with nice parts I won’t bore you with the list, but it does have a CMC 3.5 lb single stage in it. It’s a sub MOA shooter.

I experienced nothing but problems when I first got the upper. Failure to feed and extract. Long story short the gas port was drilled too small. This is a very common problem with the 6.8 spc. I tried everything before having the port redrilled including an adjustable gas block.

I won’t buy another RR in 6.8 based on my experience. I’d look at the Wilson or an LWRCI.

Hope this helps
I know it can be aggravating when you don't know why something is happening but it takes about 30 second to drill out a gas port with a cordless drill. I don't know what size RRA drills but you can't use the same size port in a 6.8 that is used in a 223. It is typically .005-.006 larger. Also if the barrel is ported for use with a standard carbine spring and buffer and someone uses a H2 or SSS spring it can cause short stroking. If there are gas leaks at the gas block/gas tube those leaks can cause short stroking. If the barrel is ported to run on factory ammo producing 54000psi and the reloads only produce 48000 psi it can cause short stroking. Wrong powder choice doesn't produce enough pressure can cause short stroking.
 
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J.Boney

Resident Sheepdog
May 10, 2006
661
120
43
48
NC - USA
#86
View attachment 7002238
This is a buck that I took with my Rock River upper. The barrel is from Rock River as well. It’s an 18” barrel with their stupid muzzle device that features teeth for some reason. The lower is an Aero with nice parts I won’t bore you with the list, but it does have a CMC 3.5 lb single stage in it. It’s a sub MOA shooter.

I experienced nothing but problems when I first got the upper. Failure to feed and extract. Long story short the gas port was drilled too small. This is a very common problem with the 6.8 spc. I tried everything before having the port redrilled including an adjustable gas block.

I won’t buy another RR in 6.8 based on my experience. I’d look at the Wilson or an LWRCI.

Hope this helps
Dang Dude, nice shooting. That’s a damn big deer. Makes N.C. Bucks look like dogs.. Glad you got the rifle shooting and feeding..
 
Likes: Climate17
Nov 18, 2011
76
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#87
I know it can be aggravating when you don't know why something is happening but it takes about 30 second to drill out a gas port with a cordless drill. I don't know what size RRA drills but you can't use the same size port in a 6.8 that is used in a 223. It is typically .005-.006 larger. Also if the barrel is ported for use with a standard carbine spring and buffer and someone uses a H2 or SSS spring it can cause short stroking. If there are gas leaks at the gas block/gas tube those leaks can cause short stroking. If the barrel is ported to run on factory ammo producing 54000psi and the reloads only produce 48000 psi it can cause short stroking. Wrong powder choice doesn't produce enough pressure can cause short stroking.
Thanks, like I said I solved my problem.

I love the 6.8 round they can take big animals clear out to 300 yards.

With that said they are a tricky build and I was inexperienced which lead to a frustrating situation. I wouldn’t be afraid to build one now but that was hard won knowledge.

If I was wanting something that worked out of the box I’d turn to a 6.8 spc specialist.
 

Stooxie

Sergeant of the Hide
Oct 11, 2018
153
91
28
#88
Thanks, like I said I solved my problem.

I love the 6.8 round they can take big animals clear out to 300 yards.

With that said they are a tricky build and I was inexperienced which lead to a frustrating situation. I wouldn’t be afraid to build one now but that was hard won knowledge.

If I was wanting something that worked out of the box I’d turn to a 6.8 spc specialist.
Did you build that upper or buy it complete from RRA?

-Stooxie
 
Nov 18, 2011
76
3
8
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#89
Thanks, like I said I solved my problem.

I love the 6.8 round they can take big animals clear out to 300 yards.

With that said they are a tricky build and I was inexperienced which lead to a frustrating situation. I wouldn’t be afraid to build one now but that was hard won knowledge.

If I was wanting something that worked out of the box I’d turn to a 6.8 spc specialist.
Did you build that upper or buy it complete from RRA?

-Stooxie
I can see how that would be confusing. I’ll clarify quickly.

I purchased a complete upper from RR.

I built the lower.

I then had to chase the demon through the gun. I started by experimenting with buffers, and moved through the lower components.

Then I had to tear apart the factory assembled upper. That’s when I finally discovered my true problem was the gas port was drilled too small. Then since it was already torn down I cerekoted it and reassembled.

Was it true build no, it was an unbuild of sorts.