So is 6.8 spc the VHS, and 6.5 grendel now the Betamax?

[jbech123]

Float Pilot why don't you just shoot SSA loaded ammo, 110 Accubond at 2680 fps from a 16" barrel?

Actually the site you mentioned shows the load at 2580fps commercial, but in combat it's 100fps more?

 

[Bigfoot]

LOL Read the link. They will sell the Combat 2680 fps loads to you only if you state that you have the improved chamber. If you have the old Remington designed chamber then you are limited to the Commercial 2580 fps loads.

Folks it's not rocket science. Two things will allow you to reach the original goal of 2800 fps and even surpass it with carefull reloading. Just two things, the improved chamber and a slower twist barrel. It's really not all that difficult to remember.

I give up. Im out.

Bigfoot

 

[Float Pilot]

Well I was writing a response and my computer locked up. Power voltage jumps around here....

Float Pilot why don't you just shoot SSA loaded ammo, 110 Accubond at 2680 fps from a 16" barrel?

I would love to try some. However I have NEVER seen any SSA ammo in Alaska. Just Hornady and maybe some original Remington.

I use SSA brass and Nosler 110 gr Accubonds for my handloads. Plus I am now trying some Barnes Triple Shock boat tails that seem to do fairly well. So far H-322 powder and CCI BR-4 primers seem the most accurate with those bullets. Sometimes additional velocity means the loss of accuracy.

Since the Hornady ammo claims a 115 gr 2,550 fps from a 16 inch barrel, but only delivers 2,400 fps in my 16 inch rifle, I am somewhat skeptical. And my rifle has a 1 in 10 twist and an improved SPECII chamber. yes I know a 1 in 11 or 1 in 12 would be better, but I could not find one.

Being an avid handloader since 1972 I am no longer amazed by the sub-par performance of most factory ammo when fired from real rifles. Particulary in cold temps, using gas operated rifles.
I'll bet things go a touch faster on a 100 degree day from a test barrel.

For combat purposes, you need something that works in a wide temp range, with moderate pressure and reasonable accuracy.

It would seem the 2,550 to 2,600 fps from either the 6.8 SPC or 6.5 Grendel is a good safe load. And about all you are really going to get FROM A 16 INCH BARREL. Both rounds are helped a great deal by a 20 inch barrel.. Which is a no brainer.

If you review the verified loads for the 6.5 Grendel on the Reloader Nest web site http://www.reloadersnest.com/frontpage.asp?CaliberID=365
you will note that most of the verifed loads were fired in 20 inch barrels.
They are obtaining 2,634 fps for a 108 grain, 2,689 for a 110 grain, 2,499 for a 123 grain and 2,420 for a 130 grain bullet.

If you reduce the loads by 100 fps for a 16 inch barrel, (25 fps per inch of barrel as seems standard for this cartridge power range) then you end up right in the same velocity range as the 6.8 SPC with a 16 inch tube.
The 6.5mm having a better BC will retain velocity somewhat better, but within actual combat ranges of 300 meters or less, it is a moot point.


Here is a 108 grain 6.5mm boat-tail with a BC of .478

Muzzle 2550 FPS
50=== =2458
100 ====2367
150 === =2279
250 ====2108
300 ====2024
350 ====1943

6.8mm with 110 grain Boat-Tail with BC of .377 at 2550 fps
Muzzle= 2550 fps
100=== 2315 fps
150=== 2203 fps
200=== 2093 fps 5 inches low with 100 yard zero
250=== 1987 fps 10.5 inches low with 100 yard zero
300=== 1884 fps 18.0 inches low with 100 yard zero

By the way: The 62 grain 5.56mm boat-tail has a BC of around .270.
If fired from a 14.5 inch M4 carbine at around 2,800 to 2,850 fps, it ends up at around the same velocity as the 6.8mm at 300 yards. It is also within 2 inches as far as drop is concerned. At 300 yards the 110 grain 6.8mm has just under twice the calculated muzzle energy as the 5.56mm bullet.



So at 350 yards the 108 grain 6.5mm boat-tail is going about as fast as the 6.8mm 110 grain boat-tail (BC of 377) at 250 yards. Both being fired at 2,550 fps.
Advantage Grendel by 100 yards if you can find one, get ammo and make it run reliably.

Yes you can hot load the 6.5 grendel as well. Just check out the bolt failures mentioned on the Grendel site.

Personally I think that the short barrel (14.5 in) of the 5.56mm M4, was just asking for trouble. As was overstabilizing the 62 grain M-855 ammo with the 1 in 7 twist. Thus making the problem and search for something better more compelling.


x

 

[Coronach]

I still don't understand why they have to make the new cartridge fit in the M4 mags.
Isn't the army planing to introduce a new polymer mag to the troops?
So you plan to rearm with different caliber, plan to introduce new mags, and plan to replace the aging M16's/M4's. Now. what's the point for the mag size rquirement? They'll have to pay full price for the new mags anyway.

I concur.

The .mil seems to be engaged in two simultaneous lines of development that seem to ensure that nothing gets done. No one seems to be completely happy with the issue carbine or the issue round. So, naturally, they're looking at a new line of rifles based around the round they don't completely like, and a new round to go into the rifle they don't completely like. Meanwhile, everyone is saying (correctly) that any advance they make by switching guns or rounds will be incremental, and thus possibly not worth doing.

I say start from scratch and try to come up with a better round and a better rifle. Release the cartridge from the requirement to fit in the M16 magwell (that's the restriction, not the magazine), and don't build the rifle around the 5.56 round.

Mike

 

[gvnwst]

I say start from scratch and try to come up with a better round and a better rifle. Release the cartridge from the requirement to fit in the M16 magwell (that's the restriction, not the magazine), and don't build the rifle around the 5.56 round.

http://thehighroad.org/showthread.php?t=292713&highlight=ultimate+combat+round

I think they did pretty good here.

 

[HorseSoldier]

The intent with 6.8SPC was a low cost performance boost to the M4. The people doing development on it originally did not have the funds or the authority to start procuring weapons with redesigned magwells and such.

Since SOCOM decided not to adopt 6.8SPC, there has been extremely little further R&D on the round by the military (more than Grendel, but a 500% increase over zero is still not a very impressive number ).

The big money, Big Army program is LSAT, which is another leap ahead technology deal kind of like the OICW -- though hopefully it will work better than that.

 

[Float Pilot]

The big money, Big Army program is LSAT

If they get any money at all over the next few years.
I'll bet more money will be spent on buying flat screen tvs and new carpeting for govt' assisted housing than gets spent on Mil Small Arms R&D.

 

[bearwolf]

Remington will probably support the 6.8spc about like they supported the 7mm stw when their new pet 7mm Ultra came out. Especially with their "new" 30 rem AR supposedly coming out in 2009. I would kiss the 6.8 goodbye on their part. There as bad as a child looking for a new toy after he done got one that he played with for all of a week and is now bored with it.

 

[GTSteve03]

I thought the 77gr 5.56 loads were doing so well with ballistics and stopping power that they kind of gave up on the 6.8?

I am by no means a 5.56 fan, but the ability to make shots out to 600+ yds with the 77gr loads seems a lot more useful than a small increase in stopping power with the 6.8s that have an almost rainbow trajectory in comparison.

 

[HorseSoldier]

I thought the 77gr 5.56 loads were doing so well with ballistics and stopping power that they kind of gave up on the 6.8?

Basically, yes. The final analysis of the combat trials for the 6.8SPC downrange concluded that SPRs shooting Mk 262 was a more logistically feasible solution to the same problem 6.8SPC was supposed to address.

The 6.8 proponents actually involved in the R&D, like Dr Roberts, make the argument that 77 grain is better, but still not as good as 6.8SPC, which may be true, but SOCOM wanted to see a bigger margin of benefit from a new cartridge before they'd spend the money to completely sever their attachment to the rest of the .mil logistics system as far as small arms ammo went.

 

[Float Pilot]

From a 14.5 inch M4 carbine, you are doing well to launch a 77 grain .223 caliber Open Tip Match boat-tail at 2,600 fps.
The BC of commercially available 77 grain .223 caliber OTM bullets range between .340 and .389 for the Bergers.

At sea level at 32 degrees the Max Point blank range is 251 yds when zeroed at 214 yds.

If you use a 100 yard zero for a 77 grain .223 with a .360 BC
Range...Drop....VEL........Energy
Muzzle..-1.5......2600fps..1156 ft Lbs
50........0.0. .....2476..... .1048
100 .....0.0 ......2356 .......949
150 ....-1.5 ... ..2240 .......858
200 ....-4.8.......2126..... ..773
250 ...-10.0 ......2016........695
300.... -17.3.... 1909........ 623
350......-27.0 ... 1806 .......557
400..... -39.4.....1706...... .498
450......-54.8.....1612....... 444
500..... -73.5.....1521....... 396

I am by no means a 5.56 fan, but the ability to make shots out to 600+ yds with the 77gr loads seems a lot more useful than a small increase in stopping power with the 6.8s that have an almost rainbow trajectory in comparison.

The flight path of the 77 grain OTM with a muzzle velocity of 2,600 fps from a 14.5 inch M4 carbine is always within 2 inches of the flight path of a 110 grain 6.8 caliber boat-tail with a muzzle velocity of 2550 fps from a 16 inch barrel.
In fact, at 300 yards they are only 0.70 of an inch apart with both rifles being zeroed for 100 yards.

HOWEVER, The larger, heavier bullet of the 6.8mm has 500 down to 200 more ft pounds of energy at all ranges to 500 yards compared to the 77 grain OTM.

The point blank range (combat sighting range is only 3 yards shorter with the 6.8mm.

Had they used the 6.5mm projectile in the 6.8SPC case, as was experimented with, the long range trajectory game would have been won hands down by the 6.5. But, as in all things military and Govt' they found a way to mess with a good thing.


x

 

[innerpiece]

whats a betamax........

 

[GTSteve03]

The flight path of the 77 grain OTM with a muzzle velocity of 2,600 fps from a 14.5 inch M4 carbine is always within 2 inches of the flight path of a 110 grain 6.8 caliber boat-tail with a muzzle velocity of 2550 fps from a 16 inch barrel.

That's nice, but how about doing an accurate comparison between the two and putting the 6.8 in a 14.5" barrel or pushing the 5.56 up to a 16" barrel? Otherwise, your numbers are meaningless.

 

[HorseSoldier]

The flight path of the 77 grain OTM with a muzzle velocity of 2,600 fps from a 14.5 inch M4 carbine is always within 2 inches of the flight path of a 110 grain 6.8 caliber boat-tail with a muzzle velocity of 2550 fps from a 16 inch barrel.

The SOCOM solution was to issue SPRs with 18" barrels for use with Mk262, not to issue Mk262 for use with M4s (though it has been used in them when available in sufficient quantity subsequently).

Had they used the 6.5mm projectile in the 6.8SPC case, as was experimented with, the long range trajectory game would have been won hands down by the 6.5. But, as in all things military and Govt' they found a way to mess with a good thing.

My recollection of the story is that 6.8mm gave better barrier penetration and terminal ballistic performance than 6.5mm, which were also significant considerations.

 

[gvnwst]

My recollection of the story is that 6.8mm gave better barrier penetration

I heard this too, but it doesn't make sense. A lower SD, (most likely) lighter bullet going just faster would not prenetrate as much. As a higher SD, heavier, but slightly slower one.

 

[HorseSoldier]

I don't know what bullet weights they were using in the 6.5mm test cartridges, but doubt they had bullet weights or BCs as high as the bullet weights Alexander Arms is using in the Grendel, since they were testing 6.5mm versions of the SPC case geometry, rather than the Grendel case, etc.

 

[gripper]

"What is theaverage cruising speed of the Belgian Swallow?"...

 

[Float Pilot]

My recollection of the story is that 6.8mm gave better barrier penetration and terminal ballistic performance than 6.5mm, which were also significant considerations.

From what I read from the original reports /studies. They found that the 7mm test projectile had the best terminal performance in test medium, while the 6.5 had the best ballistic downrange performance. Those advocating both sides compromised at the midway point 277 caliber.
Barrier penetration has lots of variables with bullet construction. Depending on what the testing parties want to prove or disprove can make a big difference in what they try.

That's nice, but how about doing an accurate comparison between the two and putting the 6.8 in a 14.5" barrel or pushing the 5.56 up to a 16" barrel? Otherwise, your numbers are meaningless.

It was my understanding that the M4 sized 6.8mm SPC chambered carbines being supplied for field testing had 16 inch barrels. Compared to the 14.5 inch 5.56mm barrels already being used for the M4s. I may be wrong in that assumption.
Thus my comparison was based upon assumed systems in use. The whole point being,, is a 6.8mm carbine better than the issue M4 carbine?
It was also based upon my own Chrongraph testing and actual velocities obtained and not the company line...I only have a 16 inch 6.8 to draw data from, plus the data I previously recorded using my issued M4 carbine and the issued M16A2 before I retired a year ago.

EDIT: Come to think of it, I do have a 16 inch 5.56mm AR-15 Bushmaster around here someplace. I could try a few brown tips (77 grain OTM) through it tommorrow. It is a 1 in 9 twist so it may shoot a touch faster than the 1 in 7 twist. Plus it probably will not group worth a darn, but I could get chronograph results. We have about 4 hours of enough light for chronograph use this time of year. As long as it does not snow heavily.

Firing the 6.8, 6.5 and 5.56mm from a 20 inch A2 sized rifle would be a good comparison as well. Personally I am thinking about rebarreling my 6.8 to a 20 inch.
Of course once you start giving barrel length and velocity back to the 5.56 round it starts to look OK again too.

 

[HorseSoldier]

I could try a few brown tips (77 grain OTM) through it tommorrow.

Mk262 is plain tipped.

Brown tip is supposed to be an SBR-optimized 70 grain load, though I'm not entirely sure it actually exists anywhere except the internet.

 

[Float Pilot]

I thought is was referring to the plain brown copper jacketing of the MK 262 stuff. I have never seen or heard of anyone painting actual brown paint on a 5.56 projectile. You would think that would be very hard to see in certain conditions. Is that 70 grain stuff a real bullet or some sort of plastic type stuff?

Does anyone know what the powder and charge is for the MK 262 stuff?

I would rather try to duplicate the load than blow rounds from the only box of it I will probably ever have. I have a few Nosler 77 grain HPBTs that used to work in my old 20 inch HBAR 1 in 7. I don't think they will stabilize in the 1 in 9 twist, but for velocity they should be close enough.

 

[crushbup]

6.8 is a Kentucky Rifle, 6.5 is a phased plasma rifle in the 40 watt range.

 

[Dr. Tad Hussein Winslow]

Why doesn't someone make a "poison pill" bullet for each of these cartridge, with an air pocket in the tip? I would think that a 105/108 grain 6.5 in a poison pill config would have a great BC, get great velocities, and have devastating terminal results, outperforming the 6.8.

 

[HorseSoldier]

I thought is was referring to the plain brown copper jacketing of the MK 262 stuff. I have never seen or heard of anyone painting actual brown paint on a 5.56 projectile. You would think that would be very hard to see in certain conditions. Is that 70 grain stuff a real bullet or some sort of plastic type stuff?

I don't know. I've shot a whole bunch of Mk262 and never heard it referred to as brown tip. We always either referred to it as "262" or, more usually, just as "77 grain."

There are internet rumors of a "brown tip" round with some sort of faster burning powder to get better performance out of 10.5-14.5" barrels, and using some sort of 70 grain solid copper, expanding bullet.

I think, however, they are just rumors. I spent the last four plus years as a support guy in an SF unit and dealt with a lot of more exotic sorts of ammunition. I never saw any "brown tip" ammo in person, never read official about it, never saw a DODIC for it, etc. I guess it might be something available to the folks in JSOC, who get access to various other stuff that "white side" SOF units don't see, but in his 2008 briefing paper for NDIA Dr Gary Roberts doesn't make any mention of a production, issue round with the characteristics "brown tip" supposedly provides (actually, quite the contrary, he basically says we need to develop one).

The sources of the "brown tip" story seems to be Defense Review and Strategy Page online. Defense Review has made various errors along the way, and owned up to them when it comes to light (i.e. they broke the "story" about the USMC switching to 45 GAP Glocks, which was 100% false). Strategy Page's journalistic standards are so poor as to be barely worth mentioning. So the whole thing may be an internet myth -- if so, it's unfortunate, since googling it looks like it's fueling left-leaning internet sites claiming US forces are engaging in war crimes by using expanding bullets.

 

[gvnwst]

Why doesn't someone make a "poison pill" bullet for each of these cartridge, with an air pocket in the tip? I would think that a 105/108 grain 6.5 in a poison pill config would have a great BC, get great velocities, and have devastating terminal results, outperforming the 6.8.

Well, how hard would that be? It is pretty simple and cheap to make "normal" FMJs, but they might turn that down becasue of cost. And the 6.5g allready outperforms the 6.8 terminally i seem to recall......

 

[vmfrantz]

All I know is we need a new caliber fast. Heard a rumor the 5.56 is no longer capable of killing just like the 30-30.