Armed Polite Society
Main Forums => The Roundtable => Topic started by: makattak on March 11, 2009, 08:53:53 AM
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Alright, I'll probably take this over to THR as well, but I'm considering a 6.8 SPC upper for my AR.
I have only recently learned of this caliber and am intrigued.
Does anyone have any experience/thoughts on this cartridge for me to consider before I make the plunge?
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The cartridge is a lot like a .223/5.56 necked up to .270.
Bullets are heavier than .223, with a bit of velocity loss. Still, it hits harder than .223, especially if you're comparing milspec ammo in both calibers.
With softpoint ammo, it makes a better big game (i.e., deer) round than .223.
Ammo is much, MUCH less common than .223. Ask for 6.8 SPC ammo in many sporting goods stores, and you'll get a blank look. (Uh . . . I guess with today's hiring practices, you can get the same blank look if you ask for .22 rimfire, but I think you know what I'm getting at.)
Bottom line, from a ballistic standpoint, there's nothing wrong with the round; but due to availability issues, I have reservations about it's practicality. If you want to hunt/plink with an AR and will provide your own ammo 'way in advance of your needing it, fine.
But for a "go-to" rifle in case of trouble (civil unrest, zombie swarms, whatever) I personally see little advantage over .223; not being in the military, I'm not bound by the Hague Accords in ammo choice, so I'm confident that the .223 ammo I'd use would work just fine. And .223/5.56 ammo is VERY common. So I don't see a 6.8 SPC, 6.5 Grendel, or anything of the sort showing up in my gun safe anytime soon.
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I haven't had any issues fining ammo for mine. The problem I've had is finding magazines. Personally, I like the 6.8 better than the .223/5.56 rounds.
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I had assumed the 6.8 used the same magazines and .223. Bad assumption? Are there other (upper, lower, etc) differences I'm not aware of too?
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I had assumed the 6.8 used the same magazines and .223. Bad assumption? Are there other (upper, lower, etc) differences I'm not aware of too? I had assumed the only difference was probably chamber, and recoil/buffer spring.
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Logistics aside, It's probably one of the best options for the AR15, but it's not without pitfalls. Remington screwed up the chamber dimensions when they submitted it to SAAMI, so you should be looking for either a SPC2 or DMR chamber. Fortunately, DPMS and Model 1 Sales are the only ones still using the SAAMI chamber. Most manufacturers use the same blanks that were intended for the 270 Winchester, a 1:10 6 groove. These work, but a 1:11 through 1:13 with 3 or 4 grooves will lower the chamber pressure and allow higher velocities. Also, your upper and barrel extension need to have M4 feed ramps. The only different parts are the barrel, bolt, and magazines. All other parts are the same as 5.56. If I was looking for one now, I'd get on the list at Titan Armory (http://www.titanarmory.net/id69.html)
For ammo, stay away from Remington, it's anemic and not accurate. I've heard that if you pull the bullets, reweigh the charges, then reseat and crimp them they are much better, I don't think it's worth the effort though. Remington also lists the velocity from a 26" barrel, and it's still slower than standard ammo from SSA (http://www.ssarmory.com/) from a 16" barrel, and they have hotter loads they will sell you if you have a SPC2 or DMR chamber. There is brass available for both large and small primers, Large will deliver a higher velocity, while small will have a more consistent velocity with a smaller extreme spread.
Magazines are available from PRI, Barrett, and C Products, with C Products supplying OEM mags to companies like Stag, Bushmaster, DPMS, etc. There is talk of another magazine group buy at http://68forums.com/ (http://68forums.com/), you might want to sign up there. The last group buy was in December, and they were able to deliver mags when I couldn't find them anywhere.
http://demigodllc.com/articles/6.8-mm-spc-cartridge-history-development-hornady-stag-arms-carbine/ (http://demigodllc.com/articles/6.8-mm-spc-cartridge-history-development-hornady-stag-arms-carbine/)
http://www.yuntaa.com/FileManager/DownloadAuthentication.aspx?download=&ContentID=56219979A4A26D6FE04400144FB7B71E (http://www.yuntaa.com/FileManager/DownloadAuthentication.aspx?download=&ContentID=56219979A4A26D6FE04400144FB7B71E)
http://www.dtic.mil/ndia/2008Intl/Roberts.pdf (http://www.dtic.mil/ndia/2008Intl/Roberts.pdf)
Here's my 6.8:
(https://armedpolitesociety.com/proxy.php?request=http%3A%2F%2Fi328.photobucket.com%2Falbums%2Fl342%2F1k_wayne%2Fguns%2FP2210142.jpg&hash=443212c04d194c03090d9e18a988af1e50af39ad)
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I had assumed the 6.8 used the same magazines and .223. Bad assumption? Are there other (upper, lower, etc) differences I'm not aware of too? I had assumed the only difference was probably chamber, and recoil/buffer spring.
In my research, so far I have found that people suggest a different magazine. Using 6.8 SPC in a .223/5.56 magazine will cause the mag to expand at the top and become unusable. The rounds can fit into the .223 magazine, but not well. Jamming will occur after a few rounds.
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That is what I had heard on the mags. 223 mags will work, but not reliably.
My uncle has a Mini14 in 6.8 that he was given. He said it shoots straight and he likes it a lot. He is a ranch manager though so I guess a Ranch Rifle fits nicely.
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The cartridge is a lot like a .223/5.56 necked up to .270.
It's nothing at all like that. The 6.8 SPC is based off the 30 Remington (rimless 30-30), shortened to 43mm, and necked down to .277
You can load about 3 or 4 rounds of 6.8 SPC into a 5.56 mag before it jams.
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It's nothing at all like that. The 6.8 SPC is based off the 30 Remington (rimless 30-30), shortened to 43mm, and necked down to .277
You can load about 3 or 4 rounds of 6.8 SPC into a 5.56 mag before it jams.
My bad . . . I was thinking length, and forgot the case is about 0.05 larger in diameter, for additional powder capacity.
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One issue is that the case length severely limits the bullet profile you can use. Because of the necessarily short bullet length, you aren't able to use bullets with a very good ballistic coefficient. Long range work suffers accordingly.
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Any thoughts on the 6.5 grendel?
I am very partial to the 6.5mm rounds out there.
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I love the grendel. If I was gonna do a boutique caliber in an AR that'd be it. Very efficient design, with vld's very very good long range performance etc.
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While it's true the 6.5 has bullets available that have a better BC, that's not that great of an advantage when you have a handicap of 200-300 fps from the same length barrel. Lets compare apples to apples:
6.5 Grendel Lapua Senecar 123gr (http://personalpages.tds.net/~beebew/68spc/65lapua123.txt) BC of .574
6.8spc Nosler Accubond 110gr (http://personalpages.tds.net/~beebew/68spc/68nosler.txt) BD of .410
If you If you look at the 600 yard data, the 6.8SPC has 7" more wind drift with 9" less drop. It has less energy at that range, but how much do you realistically need to poke a hole in paper at that range? 1.5 MOA at that range is not a significant difference.
If you change the 6.5 bullet from a match bullet to a hunting bullet, the numbers tilt significantly in the favor of 6.8 SPC:
6.5 Grendel Nosler 120gr (http://personalpages.tds.net/~beebew/68spc/65nosler.txt) BC of .458
At 600 yards, the Nosler 6.8SPC has 18" less drop, and 1" less wind drift than the 6.5 Grendel. If you want to compare velocity from a 24" barrel instead of a 16", please note that the 6.8SPC is capable of 2900 fps at that length, still 200 fps more than the Grendel.
In the end, they are more alike than they are different. If you are only shooting at paper, by all means, get a 24" H-bar Grendel and poke as many holes with those $44/box bullets as your wallet will allow. If your target is made of meat, neither one has enough energy past 300 yards to allow for an ethical hunting shot (Yes, I know Elk have been taken at ~400 yards with both, but IMO, neither one of those should have pulled the trigger). I went with 6.8SPC for the shorter lighter barrel, much more commonly available parts and components, better terminal ballistics inside 300 yards, and lack of bolt (http://www.65grendel.com/forum/showthread.php?t=2865) problems (http://www.65grendel.com/forum/showthread.php?t=4817).
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I think of the 6.8 as a "pocket .270".....not real interested in it on the AR platform....but in a lightweight bolt-action carbine, it could give the .243Win a run for its money.....
If I want more punch in an AR platform, I'd choose an AR-10.... :cool:
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I'm building a 6.8 SPC AR-15 at this time. Got one in .223 and wanted one in the 6.8 so I joined the group buy on THR.US. Getting the barrel from ER Shaw and a YHM flat top upper.
http://www.thehighroad.us/showthread.php?t=403454
Shopping for brass, bullets and such while the barrel is getting manufactured.
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I'm building a 6.8 SPC AR-15 at this time. Got one in .223 and wanted one in the 6.8 so I joined the group buy on THR.US. Getting the barrel from ER Shaw and a YHM flat top upper.
This is actually one of the first things I did when I moved to VA. I built mine on a DPMS lower with a Bushmaster parts kit, a Magpul UBR stock, and topped it off with a Rock River upper. I swapped out the trigger and got a smokin deal on an EOTech from work. Really happy with it. I just don't feel like spending $40 a pop for 6.8 magazines right now.
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I would go with a .260 and leave all those .277 bullets for me. =D
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I'm building a 6.8 SPC AR-15 at this time. Got one in .223 and wanted one in the 6.8 so I joined the group buy on THR.US. Getting the barrel from ER Shaw and a YHM flat top upper.
http://www.thehighroad.us/showthread.php?t=403454
Shopping for brass, bullets and such while the barrel is getting manufactured.
Please let me know how the ER Shaw barrel works- I'm very interested.
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On a more serious side I have used E R Shaw before with very good results. But I would still look at .260.
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I just don't feel like spending $40 a pop for 6.8 magazines right now.
You don't have to (http://68forums.com/viewtopic.php?f=1&t=6428)
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You don't have to (http://68forums.com/viewtopic.php?f=1&t=6428)
Sweet! Thanks. I'm not sure how I ever missed that site. Found a few cheap 25 rnd mags and even some cheaper 15 rnd P228 mags.
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Linky no worky.
It forces a registration and log-in just to see it.
Umm, no thanks. =|
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Keeps out the rif-raf that way. =D
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That's cool.
I'm more interested in the 6.5 Grendel, or building a 6.5 SPC wildcat, myself.
I have a spare pre-'94 Olympic Arms lower sitting in the gun safe doing nothing in particular...
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Keeps out the rif-raf that way. =D
And they grandfathered you in?
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Ok, bumping again as I have a follow up:
Does anyone have any experience with Stag Arms uppers?
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The only issues with the Stag 6.8 are they do not have M4 feed ramps so you may have to add them yourself, and their muzzle threading is 1/2" instead of the standard 5/8", so be careful if you change the flash hider, a 5.56 hider will thread on and ruin your day in the process.
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I have a 6.8 from DPMS but I am having problems. It will not extract a unfired cartridge. I have to use a screwdriver to wedge the bolt open. I fired 10 rounds having to use the forward assist to lock the bolt. I reloaded that brass thinking it would now be fireformed, but it still gets stuck. I know its the rounds because I can cycle the bolt open and closed just fine with a empty chamber. I am using SSA ammo. I called DPMS and they said to try Remington ammo. Any thoughts?
IKIMURA
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IKIMURA, DPMS is one of the very few manufacturers that still uses SAAMI chambers, they are notoriously tight, even for a SAAMI chamber. Head over to http://68forums.com/ (http://68forums.com/) and talk to paulosantos, he has a reamer that will update your chamber to an SPCII.
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SOO you dont think its the ammo? If its the chamber I will let DPMS take care of it. Will they charge me?
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Feel free to call them, but DPMS has their head in the sand. They will tell you the gun is not the problem. If you download this (http://www.yuntaa.com/FileManager/DownloadAuthentication.aspx?download=&ContentID=56219979A4A26D6FE04400144FB7B71E) pdf file, you can see what difference the chamber and rifling twist rate will make, it can lower the pressure up to 10K psi. Then go register on http://68forums.com/ (http://68forums.com/) and contact Paul about reaming your chamber to what it should have been to begin with.
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Are you neck sizing only when reloading? I'd be reluctant to do so in that rifle. I'd prefer to full size.
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I full size my reloads. My brand new factory ammo will not work either!
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I got cornered by either Ferris or Lou (I'm not really sure which is which) at the last Supershoot, and he proceeded regale me with stories of the cartridge's superiority... Sounds like the greatest thing since sliced bread, but if it is blown-out toward straight, it'll have a tendency to extract hard. Polish the chamber.
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Bogie, the parent case is the 30 Remington, basically a rimless 30-30 shortened and necked down. Base is .418", shoulder is .400" and 1.3" from the base.
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It's a modification of the old .30 Remington, same family as the .25 Remington and .32 Remington, as used in the Browning-Remington autoloading Model 8/81 rifles, and the pump 14/141 rifles.
They in turn were rimless ballistic clones of the .30 WCF and .32 Winchester Special, and loading data from the latter can be used for the former.
the 6.8 SPC still has a pronounced shoulder, so headspacing and extraction is really no problem.
To fit into an AR-15/M16 length magwell, those .277 bullets have to be short, so you won't be able to run the high BC numbers like the Berger .277 VLD without intruding into powder capacity.
I wanted to build a 6.5 SPC wildcat, and run .264" high-BC bullets, but again the length and powder capacity limitations keep me in the lightweight bullet territory.
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I wrote DPMS a EMAIL and a guy named Matt from Quality said to send it in and he would ream it to SPCII for me. I guess DPMS has there act together. I will let you guys know how it shoots.
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FWIW, at the Supershoot and IBS Nationals last year, had a nice discussion with the Shilen boys... They're doing some good AR barrels...
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Palmetto State Armory has C-Products 25 round 6.8 SPC magazines listed for $11.99 right now if anyone is interested.
http://www.palmettostatearmory.com/183.php (http://www.palmettostatearmory.com/183.php)