Home Forums Hunting & Shooting AR and Tactical Rifles Thinking about a 6.8 SPC upper,what do I need to know?

And...here's the chamfer, even if it is a rough one.

In my personal experience, out of short 12.5" barrels the two cartridges produce pretty much equal velocity with similar bullet weights. The Grendel just retains it farther. I'm not sure about the results in long barrels, neither cartridge appeals to me much in a 20+" tube.

What you say about the cases handling pressure is a theory that didn't hold up for me in practice. It's something the 6.8 fanboys like to repeat a lot, but my personal experience is that most of the Grendel brass can be pushed just as hard or harder than 6.8 brass. The failure modes for both, that I found, was loosening primer pockets before anything else. The smaller diameter 6.8 case should be able to handle more pressure in theory, but I ran into soft brass from both Nosler and Hornady that made reality very different from theory.

I don't know what you're talking about with the "unsupported" comment; there's something wrong with your barrel if it's unsupported in front of the case web; that sounds like more 6.8 fanboy talk IMO. I've not seen bulging of any sort in mine with either cartridge. Have you actually experience this personally?

The chamfers in those barrels above look normal. Are you saying you don't see the difference?

The chamfers in those barrels above look normal. Are you saying you don't see the difference?

bcraig.
No I never made any pistols in either caliber. I have made carbines in both with 14.5" barrels bu that's as short as I have gone. In doing 14.5" I have to permanently attach the muzzle breaks of flash hiders to make them legal so the overall length will be at 16" according to ATF

I had to look up xm68gd. I had no idea what you were talking about. But I find it's a factory round offered by federal.
Again, no info for you. I loaded all my own ammo. When I first started working with the 6.8SPC I was making brass from 30 Remington and also 30-30 by cutting off the rims and deepening the extraction groove.

Barrels: Now I can answer some questions.
For my 6.5 Gs I have used ER Shaw blanks in 1-8 twist and Green Mountain barrels, also with 1-8 twist, as well as one Pacnor 1-8" twist.

In the 6.8 bore size I have used a bunch.
I have used take-off Ruger M77 270 Winchester barrel with a 1-10 twist.
A Browning FN mauser take-off barrel with a 1-12" twist.
A Weatherby rifle barrel with a shot out throat, was a 270 Magnum. 1-12" twist
A Remington M700 take off with a 1-10" twist.
About 30 Green Mountain blanks with 1-11 twist.
About 10 ER Shaw barrels that were made on a special run with 1-9.5" twist
5 Pacnor blanks with 5 groove 1-10 twist.
About 6-7 with Shilen barrels I got from Brownells 1-10"
4 that I made with Adams and Bennet blanks I got from Midway. 1-10"

And there may be a few others that I can't remember as I write this.
What I have found is that the twist rate is being marketed like the Emperors New Cloths. Many on those the worship in that "church" try to convince others that some special twist or rifling geometry is 'the best' and "extra special" It's BS. What matters most is the quality of the bore and the care in making the barrels and chambers concentric.
This group was fired by me about 15 years ago with my 20" AR in 6.8. I saved it because it's a personal "trophy" for me. I have shot many groups of about this size with several ARs I have made, but this I shot with IRON Sights. I can't see well anymore, and even when I had 20/10 vision I could not do this on demand. As I said, it's the best I ever did. But what is interesting about this is that it was shot with a $85 barrel with a 1-9.5 twist, which I turned myself and lapped for about 20 minutes. Standard style rifling 4 grooves.
I was zeroing it with a set of irons and I had a 10 round mag. My friend bob Ellis was on the spotting scope. Shots 1-5 were low and right and bob would say "come up and left" several times and the rounds walked over on the paper until round #6 touched the corner of the square. (you see that last sighter on the target) Bob said "Come up one click and left one click and shoot me a group" I fired the last 4 rounds as carefully as I could.

Here it is.
6.8 at 100 by Steve Zihn, on Flickr

I was and I am very pleased with the accuracy, but the barrel and the rifling were not "special"

Bullets.
I have used Speer 90 grain TNTs, Remington 100 grain Core-Lokts, Remington 115 grain FMJ, 110 grain Sierra Flat base, Barnes 110 grain X bullets (old ones not made anymore) Hornady 110 grain HPs, Nosler 110 grain and 100 grain Accubonds, Hornady 130 grian flat base and Winchester 130 grain power Points.

Here is what I can tell you:
the 90 gr Speer is made as a varmint bullet for the 270 Winchester and they do not recommend using it for big game. I should have listened. Even at 2980 FPS MV instead of the 3650 to 3700 you can get from the 270 Win, these bullet come apart and penetrate extremely poorly. OK, my fault. Speer says they blow up and you know want.......they do! I am my Friend Clay killed 3 antelope with them and gave up on them for anything larger than a coyote. Yeah we kills the antelope, but by hitting them just right. After gutting therm I would condemn the use of these for any big game. Wound cavities of only about 5" deep. The most accurate bullet I have shot so far however.

Remington 100 grain. Excellent terminal effects and good but not great accuracy About 1.25 MOA is standard, but these bullets penetrate VERY well and make BIG holes. 1-1/4 MOA is fine because the round is "done" at about 450 to 500 yards and at those ranges you still have accuracy good enough to hit something 1/4 the size of a small deer's chest. When you could buy them, they were cheap and for hunting I have to give them very high marks. Sadly I think Remington has screwed up (Again) in deciding not to sell them any more.
Here is a pic of a wound made by one of them. That's my fist in the pic.
6.8 wound channel by Steve Zihn, on Flickr

Remington 115 Grain FMJ. Not legal to hunt with so I killed goats and sheep to test it. Exactly what you'd expect. Slender wounds for about 4" and then the bullet tumbles and makes erratic and pretty large wounds. All bullets exited. Plenty of "kill" but the bullet paths can turn off at times, sometimes as much as 30 degrees. Not very accurate and from my 2 guns the best I could get was about 3 MOA.

Sierra 110 Grain. Super accurate and penetrates about 1 foot deep and sometimes up to about 14" before the jackets come loose. Sheds it's jacket 100% of the time, so this would be a good deer bullet but not good for anything much bigger and not what I would choose for raking shots from rearward angles My guns shoot them under 1/2 MOA. Our Whitetails are not large like the ones that come out of the north-east or Canada, so in most cases you can get full penetrating effects on deer up to about 200 pounds.

Barnes 110 grain. Also super accurate with 5/8 to 1/2 inch being common. Too expensive to practice with however. All my kills with these were close and the effect were perfect, but I don't know at what range they will fail to open up. Maybe someone else could answer that question. One kill was on a 250 pound Mule deer hit at the point of the shoulder and the bullet exited in front of the other hip about 8". This would be one I would recommend if you can afford to buy them and shoot them in practice.

Hornady 110 grain HPs. My friend Cas got some of them from Hornady before they were even released to the public and we used them in our 6.8s for almost everything in that years season. Again, super accurate with most groups being about 5/8". BAD game bullet! If they open up at all they blow up completely. The other times they pencil through. I killed the biggest white tail of my life with this bullet with a neck shot that broke it's vertebrae, but the hole even through the bones was small enough to fit my finger tightly. Cas shot a deer about 2 seconds later and I saw the bullet hit on the high shoulder through my scope. I saw the blossom of hair and the hit was placed perfectly but that deer got into the trees and we looked for it for about 2 hours. No blood and just some hair to follow for about 30 yards. I and Cas killed 4 antelope and 9 deer that season and some of the bullets blew to pieces, but others made wounds like an arrow with a field point. For anything but paper, don't use these. My last deer was in a field next to a stand of corn about 10 acres large. I made a heart shot and the deer made it about 65 years to the corn and we tracked a very small blood trail for about 40 minutes before Cas found it dead. Wound was about 1/2 around.

Nosler Accubonds in 110 and 100 both.
Other then costing a lot, these cannot be criticized at all. Almost as accurate as the 90 grain Speer with all groups being just a ragged hole. Everything shot with either one of these died as if struck by a 30-06, and the few deer and antelope that didn't fal at the shot had blood trails measured in feet not yards. Every bullet so far has left an exit. This would be my top pic of the ones I lest here. It might have been the 110 grain Remington, but Remington made that impossible for you. The Accubonds are match accurate, and in that way they "beat' the Core-Lokts, but in the real world they both go clear through, they both give good expansion and they both work out to ranges of 350 to 400 yards. I pushed the Remington for a few years because you could buy them by the multiples of thousands for not much money and shooting a LOT of them in practice which makes the man a better shot.

A 1.5" gun in the hands of a 1.5" man shoots 1.5" groups.

A . 1/4 MOA rifle in the hands of a 6" man shoots 6 inch groups, and that is why the less accurate Remington was my favored bullet for a long time, even though there were others that shot better over a bench rest. I don't carry a rest when I hunt, but shooting 5000 to 7000 a year made me a VERY good marksman with my ARs.
Anyway, the Accubonds are outstanding.

130 grain Hornady Spire point and WW 130 grain Power Points. Both loaded to about 2300 FPS. Kill just like they were fired from a 270 Winchester. Band-Flops are common. So are exits. Not all that flat shooting, (about like a standard load from a 303 British) but in areas where you can't see 300 yards, it didn't matter at all.
No bad points to say about either.

The Hornadys shot about .8 in my guns and the Winchesters shot about .6. For hunting on the river bottom either of these might be my choice. Through and through wounds with very short blood trails, or none when they hit the ground as you are still hearing the shot. I don't know what more you could want.

I have several friends that also use 6.8s and they have used a few other bullets, but these above are the ones I can tell you about from personal experience

The boogered chamfer photo is a 5.45x39 and came from this thread- http://www.m4carbine.net/archive/index.php/t-18015-p-5.html
It did not cause any of the belted Grendel magnum case I posted photos of so you can stop using that as an excuse.

Are you goofy? You're the one who posted it. Maybe try posting something from your own experience, as I have, instead of random stuff you've found online. Some of the stuff you're saying sounds exactly like all the other 6.8 fanboys who've never actually owned a Grendel but somehow know all about it... This kind of thing is exactly what I was referring to with my comments above about the 6.8 fan club.