More 6.8SPC Info

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mattf7184

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"Here is the latest poop on the 6.8 cartridge. This information comes from a Remington employee who's name I still have to keep private. From an email dated 6 July 2004...

"The 6.8 thing is moving along but slowly. The only significant ammo we have sold has been to Barrett as far as I know. There is a run going on now I believe and I believe it will be commercially available but we already have a significant amount of orders mainly from distributors.

The pressure problem (along with some others) have for the most part been fixed/addressed. The round is NOT being used overseas by anyone despite what you might read. DOD JAG had given a preliminary approval for use of the round but then it was found that the round was not legal so it was withdrawn. SOCOM has announced that it is not interested in another caliber as has the Infantry center. There is talk by all of the gun writers but that is about it. The FBI tested it and it was rumored that they loved it but we haven't heard anything back.""

Taken from olympic arms forum, written by Rattler.
 
Zak, they increase pressure to get velocity and accuracy suffers. They decrease pressure to get accuracy and velocity suffers. Problem. (Also, and this is little-mentioned except by firearms engineers: if you increase pressure too much you increase bolt-thrust such that the bolt is slamming violently to the rear and wearing out or breaking parts earlier than normal.) However, Remington is a big company and they know how to make ammo, so solutions should be forthcoming. But, how much R&D are they willing to devote if there are no big military orders pending?

A guy calling himself Kel over at Lightfighter Tactical Forums had this to say during a recent thread on the 6.8 SPC:

"Interestingly, I was out having some dinner with some fellow firearms manufacturers (brands that we all know and love, all with current military contracts) and the caliber subject came up. . . . The general consensus was that it's dying on the vine.

"I'm certain time will tell whether or not it will be destined to be a boutique wildcat caliber or if it's the next gift from the ammogods, but at least some manufacturers aren't seeing a lot of hope for it right now.

"Anyone that attended the SOCOM Small Arms Advance Planning Briefing To Industry last month -- feel free to post the quotes from the talk on SOF caliber selection. I never saw so many industry people sit up and listen so fast when they addressed that subject.

"Eh, end of story is: When the ammo floodgates open up, will people buy it or not? We're all in wait-n-see mode, and from what I gathered at SOF, so is 95% of SOCOM.

"Kel (don't shoot the messenger, even if it's with 5.56mm)
Posted: 29 June 2004 02:36 AM"

Kel's statement was, of course, immediately disputed by 6.8 SPC fans. The whole thing remains an interesting state of affairs, indeed.

John
 
With regard to accuracy vs. velocity-- do we have any more details? All barrel lengths? All bullets? Just production? I'm pretty sure it's possible to handload ammunition which is both accurate and fast, based on a telephone a conversation I had back in March which someone who had, at that time, been loading 6.8 for a while.

Is Kel, the Kel from Gemtech?

Remington needs to get their $%^# together with ammo production. Or release a load of brass into the market so some enterprising guys with a few Dillon 1050's can get going. Jeesh.

-z
 
I have suspected that there was some air in the 6.8 SPC numbers. It just never added up. I don't know what the specific problem is, but I'm leaning toward not being able hit their velocity goal without going badly over reasonable pressures.

It also doesn't suprise me that the military isn't interested. I don't agree with the decision, but it doesn't shock me a bit.

I am concerned that large scale brass/ammo production will never happen. I would still like to have one.


David
 
1*,

There's a guy over on ARFCOM fireforming .30Rem brass into 6.8SPC brass s_s74, I think is his handle. If you are desparate for brass, that might be a source.

-z
 
Thanks Zak,

I'll hang on and follow the drama a bit longer. I'm not really an early adopter of new technology. When the brass starts flowing, the magazine issues are resovled and the new wears off I'll look very hard at it. I'm a handloader and like to tinker, but reforming brass for a semi is above and beyond the call!

How are the handloading results going?



David
 
1*,

I've heard from one or two people that PRI is shipping 10-round magazines now. Hopefully this means the 28-rounders are finally right around the corner.

The handloading results have been stalled. I've got about 150 accurate-but-slow plinker loads (VV-N135, 110gr VMAX) all set, and a bunch of preprod ammo I have to pull.

I need to get my hands on two or three different powders that nobody around here stocks (N530, N133, and one other). If I can track some of that down this week, I'll resume experiments in mid/late July when I get back from vacation.

I've been busy doing load development for 50BMG, building some AR15's, and debugging my AR10 & SV limited gun for the last month...

-z
 
Change rifling for the accuracy problem?

Not sure what they are experimenting with all together. seems like if the increase in velocity effects accuracy maybe they could get that velocity where they want it and experiment with rifling and or bullet design.. ?
Or am I off?
 
I forgot--is 6.8 SPC just a necked-up 5.56mm, or did they go with a larger case diameter like the 6.5 Grendell?

If they can't get the desired velocity without cheap-ammo-in-cheap-gun accuracy, then it may be time to give the Grendell a look. Seeing how they do with production barrels and production ammo could prove either round's true worth--or lack of it...
 
that is interesting to hear. My friend who finished BUD/S in December told me recently he was looking forward to the 6.8mm M4.
 
It's based on the 30 Remington case.

Until I get more data, I think this velocity vs. accuracy thing is overstated or misunderstood.

Most match rifles get more accurate at max loads, or slightly beyond. High-Power shooters are loading primer-popping hot loads on the long ranges with great accuracy. We (meaning us handloaders) have a variety of powders in the rifle speed & density range to try, and commercial loaders have a wider variety of non-canister powders to use.

If you have an accurate rifle and consistent loading practices, you can make the system accurate with full power loads -- that holds in just about every case. 6.8SPC will not be somehow magically different.

Over in this ARFCOM thread, we have proof of accuracy with the green-box Remington production ammo (0.75MOA). That factory ammo should meet the stated velocity goals (2800 from 18", 2650 from 16", 2400 from 12").

-z
 
Since we touched on velocity here, I have some data from last weekend.

My preproduction Remingtno 115gr OTM was shooting at 2750fps.

My handloads using the 110gr VMAX (BC = 0.370):

With N135, topped out at 2530fps (my plinking load up to now).
With N133, topped out at just under 2600fps.
With RL10, topped out at 2670fps.
AA1680 is too fast.

Also note that the BC of the 110gr VMAX is higher than the BC of te 115gr OTM.

-z
 
How come you are having problems getting to velocity remington claims to get or has gotten? Just since it is new caliber?

Also, how was accuracy?
 
To be clear, the factory preproduction ammo I've got is shooting at 2750fps, which is only 50fps short of the published values from a 24" barrel. My barrel is 18". This preproduction ammo has known problems with powder clumping and accuracy. I expect the production ammo to be slightly faster.

Why am I having trouble meeting 2750fps with my handloads? Fundamentally:
  1. I only have access to commercially-sold ("canister") powders, not the non-canister powders manufacturers can get
  2. I can't devote all my money and time to buying every possible canister powder and experimenting with it.

Coming up with loads essentially from scratch, with no load data from any official source, is challenging. The case capacity of 6.8SPC is small, too, which means you need a dense powder, but slow enough to take advantage of the barrel length.

-z
 
With regard to accuracy, I don't think we'll have to worry. People have made accurate guns and loads in just about every rifle caliber. Heck, even a "good" AK can shoot 1MOA with quality ammo. There's nothing magically different about the 6.8 in terms of accuracy, and the AR15 is a pretty easy platform to make accurate.

Once the bullet is out of the barrel, we can characterize the accuracy at 100 meters by measuring the group size, and the ballistics by measureing the velocity at the muzzle. Using those two, we can model the trajectory out to whatever distance we want, just like we do for other calibers.

Here's a ballistic comparison of three accurate semi-autos I shoot.

The 6.8 is the PRI/MSTN gun (18") - assuming I can load 1MOA or better at the velocity used.
The 308 is my JP built AR10 (20"), shoot 0.6MOA pretty consistently with FGMM 168.
The 223 is my JP CTR-02 3Gun rifle (20"), shoots 0.25-0.5 MOA consistently with BH75.

I'm using measured velocities in all cases. In 6.8SPC, I am using only the velocity I've achieved with my handloads already, not what I expect to get.

Max distance is listed as 800 yards, since all of these will get iffy past that distance. Just three weekends ago I was hitting a 10" plate at 800 yards 80% of the time with the AR10 (misses due to wind changes).
Code: 
 _BC_ _MV_         0     100     200     300     400     500     600     700     800 | YARDS
0.370 2670 >   -2.54   -0.00   -3.31  -13.87  -33.06  -63.36 -106.72 -167.39 -247.96 | > 6.8SPC 110gr VMAX
                        0.00    1.58    4.42    7.89   12.10   16.98   22.80   29.60 MOA
                2667    2431    2208    1995    1797    1611    1446    1299    1180 | fps, velocity

0.395 2670 >   -2.54   -0.00   -3.24  -13.54  -32.14  -61.26 -102.56 -159.81 -235.18 | > 223REM Black Hills 75gr
                        0.00    1.55    4.31    7.67   11.70   16.32   21.77   28.07 MOA
                2667    2446    2235    2034    1846    1667    1506    1360    1237 | fps, velocity

0.447 2575 >   -2.54   -0.00   -3.56  -14.43  -33.69  -63.38 -104.82 -161.35 -234.58 | > 308WIN FGMM 168gr
                        0.00    1.70    4.59    8.04   12.10   16.68   21.98   28.00 MOA
                2573    2381    2197    2021    1855    1696    1550    1416    1298 | fps, velocity

As you can see, the drop tables are within 1 MOA out to 700 yards, and the velocity is pretty close too. I think the only difference the shooter will notice will be the recoil and how loud the steel goes "DING."

Here's what I think is possible in 6.8, just based on gut feel and some math:
Code: 
 _BC_ _MV_         0     100     200     300     400     500     600     700     800 | YARDS
0.370 2815 >   -2.55    0.00   -2.69  -11.86  -28.68  -55.32  -93.46 -146.85 -217.87 | > 6.8SPC 110gr VMAX
                       -0.00    1.25    3.75    6.75   10.50   14.75   20.00   26.00 Qt.MOA
                2812    2568    2337    2117    1912    1717    1540    1381    1247 | fps, velocity
With the inevitable 6.5 Grendel comparison:
Code: 
0.481 2650 >   -2.54   -0.00   -3.14  -13.00  -30.45  -57.21  -94.27 -144.40 -208.78 | > 6.5Gre 108gr
                        0.00    1.50    4.25    7.25   11.00   15.00   19.75   25.00 Qt.MOA
                2648    2466    2291    2123    1964    1810    1666    1531    1409 | fps, velocity


As comparison, here are some real long range calibers:
Code: 
 _BC_ _MV_         0     100     200     300     400     500     600     700     800 | YARDS
0.627 3000 >   -1.56   -0.00   -2.70  -10.24  -23.00  -41.90  -67.23 -100.39 -141.60 | > 6.5x284 140gr VLD
                        0.00    1.29    3.26    5.49    8.00   10.70   13.68   16.90 MOA
                2998    2847    2700    2557    2419    2285    2156    2031    1911 | fps, velocity

0.648 3000 >   -1.56   -0.00   -2.69  -10.18  -22.83  -41.54  -66.55  -99.22 -139.72 | > 7RM 168gr VLD
                        0.00    1.28    3.24    5.45    7.93   10.59   13.52   16.68 MOA
                2998    2852    2710    2570    2437    2306    2181    2059    1942 | fps, velocity

1.050 2650 >   -1.56   -0.01   -3.70  -13.12  -28.46  -50.47  -79.14 -115.61 -159.61 | > 50BMG 750gr AMAX
                        0.01    1.77    4.18    6.79    9.64   12.60   15.75   19.05 MOA
                2649    2565    2482    2400    2320    2241    2165    2090    2016 | fps, velocity

-z
 
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