6.8mm

[fletch]

does anybody have pictures of 6.8mm m4 geing used (or any info)?

[Operation Ivy]

http://www.demigod.org/~zak/DigiCam/6.8mm/medium/119_1915_img.jpg

http://www.demigod.org/~zak/DigiCam/6.8mm/medium/116_1686_img.jpg
http://www.demigod.org/~zak/DigiCam/6.8mm/medium/117_1756_img.jpg
Read this for some info http://www.demigod.org/~zak/firearms/6.8SPC/faq.php
All www.ar15.com

[Dennis G]

not an M-4 but...



http://www.barrettrifles.com/images/m468_2.jpg

Features and Accessories

·Dual Spring Extractor System
·Muzzle Brake
·Folding Front Sight and Gas Block
·5, 10 and 28 Round Magazine Configurations
·Two-Stage Trigger
·Law Enforcement and Military Configurations Available
- Retail Price $2,535
- Upper Conversion Kit Price $1,494

Additional Features
·ARMS® Selective Integrated Rail (SIR) System Fore End
·ARMS® Folding Rear Sight

[Zak Smith]

Hi guys. That's my 6.8 rifle pictured, and I'm the author of the FAQ. If you have any questions, just ask. I've been reloading 6.8 for a couple months too.

-z

[fletch]

thanks for the picks/info. any info/pics of it being used in the field?

[LordHalbert]

What is the main purpose of the 6.8 mm round ??

I mean why go to a 6.8 mm round instead of something more common like a 7.6 mm nato round ?

[Zak Smith]

fletch,

I'm neither LEO nor military, so all I've got is me at the range. As soon as I get enough brass so I can afford to lose some, I'll shoot it at a 3Gun or precision rifle match.

LordHalbert,

The whole point is increased lethality from 0-300m in an M4-sized platform -- in this case, actually an M4 platform, with a barrel and bolt switch. 308 is great, but the weapons it requires are much larger and heavier than an M4.

As for why .458SOCOM or .50 Beowulf are not considered, they are great within maybe 100m, but their trajectories fall like rocks beyond that distance. 6.8SPC will have a trajectory nearly identical to 75-77gr 5.56mm, or 150-168gr .308.

6.8SPC uses standard .277" bullets just like .270 WIN.

Check out the FAQ posted earlier for some other information.

Hope this helps.

-z

[fletch]

better balistics than the 5.56 and better acuracy than the 7.62......i think ...but it sounds like zak would know better....by the way , zak do you think the 6.8 would be a good replacement for the 5.56?

[FallenAngel]

What is the main purpose of the 6.8 mm round ??

I mean why go to a 6.8 mm round instead of something more common like a 7.6 mm nato round ?

Because the shorter barrel on the M4 plays makes the 5.56mm round less than ideal. I have yet to hear complaints from troops that use the 20" M16A2/4 rifle.

Plus the SS109 round was designed (if I am not mistaken) to go through body armor and then tumble in the target thus causing immense internal damage.

Most "terrorists" don't wear body armor so the round over-penetrates and goes straight through the target. It takes multiple hits to put down a target (not a good thing when fighting wackos who want to die anyways).

6.8 is a big bigger, slower and has a bit more "punch" which most people are hoping will solve the problem.

Me, personally, I would just buy the new SOCOM M14. Same size (roughly) as an M4, 20 round mag but more weight.

http://www.springfield-armory.com/images/rifles/AA9626Large.jpg

[Zak Smith]

With regard to accuracy.. a properly-built .308 bolt gun will shoot 0.25 - 0.50MOA consistently with good ammunition. Take a look at what GA Precision is producing. Likewise, a properly-built AR15 will shoot 0.25 - 0.5 MOA consistently with good ammo, just take a look at what JP Enterprises produces in match guns. 6.8 shouldn't be any different. In summary, any properly builtgun should shoot 0.25 - 0.5 MOA with good ammo. I don't think 6.8 has an advantage here.

With regard to ballistics/trajectory, basically a higher Ballistic Coefficient (BC) and a higher muzzle velocity are always better. M193 (55gr 5.56mm) from a 20" barrel is screaming along at 3200 - 3300fps. Even though it has a pretty low B.C. (bad), it is flat shooting out pretty far.

Contrast to a standard sniper round, the 175gr 308, which has a BC of almost 0.5 (twice better than the M193) and a muzzle velocity of about 2550 - 2660fps. The high BC will maintain that velocity longer.

The 6.8SPC will follow almost exactly the same path asa 77gr 5.56, or a 150gr 308, because the bullets have almost the same BC and they are fired at almost the same velocity.


To get an intuitive idea of the attraction of 6.8SPC, imagine shooting your M4 clone, or SPR clone, but instead of shooting 75gr match ammo, shooting rounds that have the same velocity but just over 50% more mass.

Instead of your AR15 being not legal for deer hunting (in some states .243 is the minimum), or it being on the anemic side, your AR15 is now well into deer-gun class, having ballistics pretty close to .257 Roberts.

To convert an AR15 or M16 to shoot 6.8SPC, you need a new barrel, bolt, and new magazines. Unfortunately, USGI M16 magazines do not work well at all. It's a natural idea to buy a 6.8 upper, but keep around a 5.56 upper for cheap target practice. Any 5.56 rifle should be convertible to 6.8 with some work.

-z

[wyrm_142]

Zak's right with the right ammo & gun a decent shooter can do amazing things with just about any round (5.56, 6.8, 7.62, etc). I don't claim to be anything close to decent, yet my bolt gun can do this:

http://web.pdx.edu/~schmidtk/pics/3shots.JPG

Three rounds .308 during scope sight in, 100 yards, ****e with the ground in support. I adjusted the elevation and the next round passed thru the 10.

[Supes]

I love that 3rd picture. PRI 3rd Gen handguards are nice! also the Magpul M933a. What kind of Surefire is that in the picture? maybe a C2? I can't really tell. Thanks

[LordHalbert]

I like that M14 pictured above - me wants one :)

Lethal & accurate - what more do u need?

[Zak Smith]

I think it's the Millenium Centurion model.. basically a C2 with some shock isolation, I believe.

I really like the PRI tube- also got one on my AR10. Lightweight and it doesn't get hot; enough rails for slings & bipods, etc.

With regard to the M14 or a small FAL, I think you'll find that an M4 even with an 18" barrel is smaller and lighter than a 16" FAL or M14. Consider than a 20" barrelled 308 will shoot a 150gr at about 2700fps. Cut 2 inches to 18" and you're downto 2500. Cut another 2" down to 16", and you're again down to 2300-2400fps. We're getting into .30-30 ballistics here.

A 6.8 of smaller size will still have a MV of 2800fps for the 18", and 2600 for the 16". And it will be lighter and more easily manuverable, be parts-compatible with the rest of the inventory (M4/M16) etc.

Also consider the reciprocating mass in the308 battle rifles. The bolts and bolt carriers (and/or op rods) are considerably more massive than the bolt carrier assembly and buffer in the AR15. That increased moving mass increases the effort it takes to control sight picture control during rapid fire.

-z

[Zak Smith]

More pics:

http://apollo.demigod.org/~zak/DigiCam/Shoot-2004.05.02-68/small/119_1959_img.jpg [ link to larger image ] (http://apollo.demigod.org/~zak/DigiCam/Shoot-2004.05.02-68/?medium=119_1959_img.jpg)

http://apollo.demigod.org/~zak/DigiCam/Shoot-2004-04-02/small/117_1790_img.jpg [ link to larger image ] (http://apollo.demigod.org/~zak/DigiCam/Shoot-2004-04-02/?medium=117_1790_img.jpg)
http://apollo.demigod.org/~zak/DigiCam/Shoot-2004-04-02/small/118_1808_img.jpg [ link to larger image ] (http://apollo.demigod.org/~zak/DigiCam/Shoot-2004-04-02/?medium=118_1808_img.jpg)


http://apollo.demigod.org/~zak/DigiCam/6.8mm/small/117_1743_img.jpg [ link to larger image ] (http://apollo.demigod.org/~zak/DigiCam/6.8mm/?medium=117_1743_img.jpg)

[Supes]

What brand of 6.8 do you have there? I have seen some Remington 6.8 but it's there seems to be very little of it.

[Zak Smith]

The ammo? The ammo pictured first is my reloads. (The ammo in the black stripper is Rem.) I bought two cases of the preproduction Remington ammunition with my upper back in Feb/March. I shot about 100 rounds of that, and pulled the rest into components for the brass. The preproduction ammo was supposedly produced to test Remington's line and for function testing guns -- it was inaccurate due to known powder and bullet problems at that time.

There should be news about the fixed new production Remington ammo soon. Also, magazine conversion kits (15 and 25 round) will be available real soon.

I've been loading the 110gr VMAX bullet with powders in the speed range of H335/AA2230 to N-135.

The upper was built by MSTN, it's based on a PRI barrel and forearm, and a LMT receiver.

-z

[el_kab0ng]

fletch,

I'm neither LEO nor military, so all I've got is me at the range. As soon as I get enough brass so I can afford to lose some, I'll shoot it at a 3Gun or precision rifle match.

LordHalbert,

The whole point is increased lethality from 0-300m in an M4-sized platform -- in this case, actually an M4 platform, with a barrel and bolt switch. 308 is great, but the weapons it requires are much larger and heavier than an M4.

As for why .458SOCOM or .50 Beowulf are not considered, they are great within maybe 100m, but their trajectories fall like rocks beyond that distance. 6.8SPC will have a trajectory nearly identical to 75-77gr 5.56mm, or 150-168gr .308.

6.8SPC uses standard .277" bullets just like .270 WIN.

Check out the FAQ posted earlier for some other information.

Hope this helps.

-z

I've actually handled the 458 socom, and it is a nice rig using standard GI mags. The only disadvantage other than range that I have found is the limited capacity. With a 30 round mag, you can only fit 10 rounds of 458. And unless you want a 1 second burst, all shots would be semi auto.

As for take down power, you and I both know that it is currently taking 2-3 hits from a 5.56 (at optimal distances!) to bring someone down in the sandbox. With a 458 at range (150-200Y), one round should be sufficient.

[Zak Smith]

A 150gr 308 fired at 2700fps will drop about 7" at 250 yards with a 100y zero.

A 400gr 458SOCOM fired at 1900fps will drop about 27" at 250 yards with a 100y zero.



_BC_ _MV_ 0 50 100 150 200 250 | YARDS
0.397 2700 > -2.54 -0.64 -0.00 -0.80 -3.10 -7.04 | > .308 150gr SMK 20"
2697 2586 2475 2367 2264 2164 | fps, velocity

0.180 1900 > -2.51 0.22 -0.02 -4.09 -12.70 -27.29 | > 458 SOCOM
1896 1701 1519 1359 1226 1120 | fps, velocity

[Dutchman2]

They should build the G36 in 6,8mm :D !

[Dennis G]

They should build the G36 in 6,8mm :D !

They should build a lot a rifles in 6.8

[el_kab0ng]

Out of what barrel length?


A 150gr 308 fired at 2700fps will drop about 7" at 250 yards with a 100y zero.

A 400gr 458SOCOM fired at 1900fps will drop about 27" at 250 yards with a 100y zero.



_BC_ _MV_ 0 50 100 150 200 250 | YARDS
0.397 2700 > -2.54 -0.64 -0.00 -0.80 -3.10 -7.04 | > .308 150gr SMK 20"
2697 2586 2475 2367 2264 2164 | fps, velocity

0.180 1900 > -2.51 0.22 -0.02 -4.09 -12.70 -27.29 | > 458 SOCOM
1896 1701 1519 1359 1226 1120 | fps, velocity

[Zak Smith]

I guessed at the 458 velocity based on a 16-18" barrel. The only numbers I could quickly find were based on a 24" barrel, so I knocked some off.

-z

[el_kab0ng]

Humm.. I might have to borrow the 458 again and do some 16" data gathering. I don't think there's a 20" version available, but I could be wrong.

[East]

http://www.springfield-armory.com/images/rifles/AA9626Large.jpg

now that ladies and gentlemen...is a top notch rifle.

[Zak Smith]

Some mag kits have become available.
http://apollo.demigod.org/~zak/DigiCam/6.8SPC-MAGS/small/129_2906_img.jpg [ link to larger image ] (http://apollo.demigod.org/~zak/DigiCam/6.8SPC-MAGS/?medium=129_2906_img.jpg)
http://apollo.demigod.org/~zak/DigiCam/6.8SPC-MAGS/small/129_2908_img.jpg [ link to larger image ] (http://apollo.demigod.org/~zak/DigiCam/6.8SPC-MAGS/?medium=129_2908_img.jpg)

[REMOV]

http://apollo.demigod.org/~zak/DigiCam/6.8SPC-MAGS/small/129_2906_img.jpg [ link to larger image ] (http://apollo.demigod.org/~zak/DigiCam/6.8SPC-MAGS/?medium=129_2906_img.jpg)I couldn't resist to make off topic digression: don't you think that such stock looks like be made of LEGO Technic? The same color and overall design ;)

[Zak Smith]

The Magpul stock does look somewhat "techy", but if you can get past the looks, it's all function.

-z

[Geezah]

http://apollo.demigod.org/~zak/DigiCam/Shoot-2004-04-02/small/117_1790_img.jpg

You look like a guy that did some testing and a write up on different ARs for Shotgun News back in(?) Feb?

[Zak Smith]

You're thinking of... I think.. David Fortier.
http://www.fulton-armory.com/images/david.jpg

I'm not him.. just another guy under 40 in a baseball cap.

-z

[Geezah]

You're thinking of... I think.. David Fortier.
http://www.fulton-armory.com/images/david.jpg

I'm not him.. just another guy under 40 in a baseball cap.

-z

I'll check tonight and let you know who it was ;)

[Far]

Looks very similiar to my 300 UM:

http://www.demigod.org/~zak/DigiCam/6.8mm/medium/116_1686_img.jpg

[[AFSOC]]

whoa

[Geezah]

You're thinking of... I think.. David Fortier.
http://www.fulton-armory.com/images/david.jpg

I'm not him.. just another guy under 40 in a baseball cap.

-z

You are very correct sir ;) I checked this morning.