Discussion in 'Rifle Country' started by Rokman, Sep 12, 2008.
What did you like about it better?
I chose 6.8SPC over the 6.5 Grendel for several reasons, not the least of which was due to component/rifle availability. It also helps greatly that I shoot a lot of 270; I interchange lightweight bullets between the two chamberings in my handloads. I do not shoot over 300 yards, and the ballistic advantages of chamberings like the 6.5 Grendel hold little profit for me relative to the extra cost and reduction in component suppliers that they imply.
The big turnoff for me about the Grendel was availability, but seems Bill has lightened up a bit. JT Distributing is building uppers, as is Charles Daly. Centerfire had some complete 16 and 20" uppers for $529 (with bcg).
Another factor is I mostly deer hunt with a sporter swede, so I can handload my 120 gr Core-Lokt bullets in either cartridge.
The whole SPC I, II, DMR, which twist, how many rifling, turned me off the 6.8. Probably should have quit reading the AR variant forum on Arfcom and kept what I had.
Regardless, either will do a good job.
Building the upper was a nightmare...what with many delays and difficulties in getting parts (I only bought top-end parts for it). Brass was expensive, reloading info was scarce. In the end, accuracy was good but not mythical like the caliber has been built up to be. That is with factory and many variations of reloads.
I realized I was trying to get a lightweight, handy CQB caliber with better performance than the 5.56 as well as a great long range caliber. While not completely mutually exclusive, it is difficult to do both. I still think the Grendel is an interesting caliber for what I REALLY WANTED TO DO (better ballistics, terminal out to 500 yards) the Grendel wasn't it. I sold the uppers and built a 6.8 upper.
It is showing very good accuracy (hovering right around MOA), has better terminal effect than 5.56, can hang with a 308 for the distances that I'm interested in and has the advantage of much wider distribution. Grendel needs to be less "exclusive" if it wants to make up the gap.
I've also decided that if I want a long range rifle semi-auto rifle, I should build a long range semi auto rifle...probably a AR10 in .260 Rem or 6.5 Creedmore.
I had a very long phone conversation with John Holliger of White Oak Armament. There's a lot of talk about the SAAMI vs. SPC-II chamber and the pressures created in each...his view is that it is a lot of hoo-haw about nothing unless you are trying to hot rod the cartridge and make it into a .270 Win.
Here's my 6.8 SPC AR
DPMS 5.56 lower
Stag/CMT M4 upper
Badger Gen II TacLatch
RRA 2-stage NM trigger
WOA 18" SS SPR profile barrel and bolt
PWS FSC30 flash hider / comp
YHM front sight
Brownells HK-type rear sight
MI low profile gas block
YHM FF rifle-length quad rail handguard
MI sling mounts
EoTech 511 (now with a 4x magnifier)
All three of them will work well at real combat kind of distances. If you're looking for a long range shooter, 6.5 Grendel is better than 6.8 Rem SPC, and 7.62 is better than either of them (no matter what the Grendel fanboys say).
For a fighting/tactical carbine, the relationship is reversed -- 7.62 is poor, 6.5 Grendel is better, 6.8 Rem SPC is the best of the bunch.
Now, 6.8 or 6.5 allow the same use of your existing lowers, while the AR-10 requires a whole new gun. Higher set up cost, but cheaper ammo or ammo making supplies once you're up and running, I'd think.
So, like I say, depends a whole lot on what you're wanting the gun to do.
Iamkris- that is an excellent looking 6.8 SPC. Thanks for the pic.
I like It
I have just purchased a 6.8 AR and had it set up like I wanted. I have the Douglas barrell with a 1:11 twist and just shot enough to break the barrell in. It is good for 1" group at 100yds. I got some extras on the rifle and enjoy shooting it. The first reason I bought the rifle is I just wanted one. The second reason is that I work as a Deputy Sheriff and I am impressed with the weapon over the 5.56. With the right ammo it will do most anything I want it to from penetration to knock down. Even hunting certain game. I do plan to try it out on hogs and possibly a deer this season. I am very pleased with the rifle and plan to experiment with different ammo.
You will find AR15, AR10, 6.5 and 6.8 fans out here. It is a matter of choice and the choice is yours. Good hunting!
It is a long and convoluted story...the short answer is:
* In the "early days" most 6.8 SPC barrels had 1:10 rifling. There were accuracy issues (over stablizing they lighter bullets) and some pressure issues due to "confusing" SAAMI chamber spec.
* Enter the trend for most good manufacturers moving to a 1:11 barrel. Accuracy issues seems to resolve themselves but there were still some overpressure reports. Most seemed to be related to 1) heavier bullets, 2) thicker brass 3) hot-rodded loads
* The SPC-II chamber is a "solution"...it has a more generous neck diameter and a longer throat/leade.
As I understand it, if you have a SAAMI chamber and 1:11 barrel, you are good to go for 99% of loads. SPC-II seems to clean up most of the rest of the issues.
Here's a short history from 68forums.com
What hasn't helped recently is an issue that KoTonics/Cardinal Armory has had...they are a major manf of barrels/uppers. They've recently discovered that their subcontractor that has been plating their barrels has not been doing it to spec. That has caused some potential issues with dangerous pressures being created. That's too bad...Cardinal is a stand up company and has been very forthright about what is happening. They're really taking it on the chin.
No way I'd buy a 1:9.5 or 1:10 barrel new. You wouldn't believe the velocities guys are getting with SPC ll and DMR chambered 1:11, 1:12 and 1:13 twist barrels. Yeah, 270 lite works for me. I'll be building one very soon.
They go into the practical results from different barrel rifling/twist rates, etc.
20” barrel: ave vel = 2561 fps; 10 fps extreme spread
16” barrel: ave vel = 2525 fps; 18 fps extreme spread -- lost 36 fps from 20"
12.5” barrel: ave vel = 2384 fps; 12 fps extreme spread -- lost 141 fps from 16"
10” barrel: ave vel = 2265 fps; 27 fps extreme spread -- lost 119 fps from 12.5"
7.5” barrel: ave vel = 2035 fps; 27 fps extreme spread -- lost 230 fps from 10"
FRAGMENTATION TRESHOLD - 1530-something fps
found these stats on another board some time ago, and copied the chrono data the reloader had done with different uppers (noveske, if I remember correctly).
Compare that to this data, everything here was tested using pressure trace equipment. The first page is with SSA commercial loads that everyone can buy. They will only sell thier combat loads after SSA makes sure that they are not used in Remingtons fouled-up SAMMI spec barrels.
Check out the velocities with handloads on the second page. These guys are pushing the 110s to over to 2900 fps. All with one eye on the strain gauge data to keep it safe.
See that 80 gr bullet at the bottom on the second page doing 3400 fps? That's a TSX type bullet from So Africa, very expensive. Why mention it? Because Barnes is soon going to restart production of thier old 85 TSX FB that they made for a short while. It will be much cheaper and should do 3200 easily. That's one flat shootin SOB. Blacktail deer beware.
You don't trust the penetration of an 85 gr TSX? Then shoot the 110 TSX at over 2800, some are getting over 2900. Mule deer and hogs beware.
Noslers 110 Accubond is out now. A 110 bonded hunting bullet with a decent BC at 2800-2900. Plus the 6.8 can shoot the shorter 130s at 2500-2600. Assuming the proper spec barrel is used.
Do you think these bullet manufacturers (who know thier markets very well) are bringing out these light for caliber .277 bullets for the 270 Win or 270 WSM? No, the market spoke and the 6.8 is a winner.
.223 brass with 7mm bullet.
7mm bullet goes from 100gr(TNT) to 170gr(Norma), and maybe 175 as a round nose.
OAL is 2.5 just like .223
Oops, I guess TCU is a blown out cartridge.
I just recently finished a 6.8 SPC with a Cardinal lightweight barrel, YHM low profile gas block, Clark carbon fiber handguard, CMT upper & BCG, RRA trigger, and an ACE stock. It's 6 lbs with the scope. I have yet to take it to the range, that will probably be this weekend.
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