Army selects 6.8mm as the new common round...

[HiBC]

The few Special Forces troops I know would not put "SOG" in their handle.
And they tend to be very quiet about where they have been and what they have done.
People skills are essential to their mission.

One of them is now in the R+D end of our discussion,and I don't talk about who he is,where he is,or what he has been working on.

I don't know why,but the sound of a coin dropping is in my head.

I have,however,met no less than four "Navy Seals" snipers at a local dive bar.

Not one of them had any idea what I was talking about when I asked them about what one MIL of a MilDot scope would subtend at 1000 yards for ranging purposes.

I met a "Ranger" at that same bar. He had no clue about Rogers Rules,he had no clue about William O Darby,and he could not tell me what "Pogey bait" is.
And he could not ID the three phases of Ranger school.

I'm not a Veteran. I have the Respect to make that clear.

I do have a certain BS detector. I'm not quite sure what it is alerting on.

[davidsog]

The few Special Forces troops I know would not put "SOG" in their handle.

Not exactly hiding here, bud. "Studies and Observation Group..SOG" is a Vietnam thing. I was not in Vietnam nor did SOG exist at anytime during my service. That those three letters appear in my username is purely coincidence.

I do have a certain BS detector. I'm not quite sure what it is alerting on.

Probably on your attempts to be an expert based on second and third hand acquaintances.

Just a guess.

Spend a little time on YouTube

About 5% of it is good content but it gets drowned out by a plethora of garbage.

[stagpanther]

Getting back to the 6.8--while I know the final selection will probably not be dimensionally exactly like the existing 6.8 spec--purely based on my civilian hobbiest experience of jumping on and building just about every new flavor of a new chambering for the AR platform that comes along--the 6.8 spec, like the existing 5.56, is exceedingly reliable in the crucial aspect of successfully making it from magazine to chamber in it's appointment to meet the firing pin. The rest is tweaking ballistics and bullet design after that IMO.

[JJ45]

According to one of the above links, the 6.8 spc moves a 120 grain bullet at 2400 fps. This is about what the 7.62X39 gets with 123/124 grain bullets but with a bit better ballistic coefficient but less bullet diameter.

As was mentioned above, the reliability of the round "from magazine to chamber" would be a deciding factor.

[Mobuck]

For "making gray matter splatter" at distance, it's hard to beat a 175 grain HPBT and for making bad guys stop bothering you @ 50' a 9mm sub-gun isn't so bad. Problem is finding a platform and cartridge that does both.
I will say that I have absolutely ZERO confidence in 5.56 FMJ of any description. When combining a long, heavy bullet (855--originally meant to punch a hole ) with a short barrel (14.5"), the velocity is too low to induce the destructive tumbling effect or to provide a flat trajectory needed for long range.

[stagpanther]

According to one of the above links, the 6.8 spc moves a 120 grain bullet at 2400 fps. This is about what the 7.62X39 gets with 123/124 grain bullets but with a bit better ballistic coefficient but less bullet diameter.

As was mentioned above, the reliability of the round "from magazine to chamber" would be a deciding factor.

I've done a fair amount of work with the 6.8spc case and wildcats derived from it--the case design is a very good one and if you can push the COL past 2.26--which is very easy to do even within the limits of existing weapons designs--you gain performance by being able to seat longer bullets to a longer COL while gaining additional case capacity for powder. With the 7.62 x 39 I've been able to significantly exceed the 2400 fps using a 125 gr bullet with the right powder and bullet combination, but the case design just isn't going to allow the same flexibility in longer bullets and/or longer COL. IMO it's strength--chamber and go bang every time no matter what no matter who made it or uses it--is also it's weakness in that it allows very little variation and still allow ultra reliability with the world's vast population of AK's. The stubby .310/.311 belly flops ballistically pretty quickly as the range stretches out (still wouldn't want to be hit by one though).

One of the biggest weaknesses I see in the vast majority of "hybrid" AR cartridge design barrels is the functionality of the feed ramps and barrel extension lugs--almost all of which rigidly adhere to the standard M4 type. This is what I attribute a lot of functional reliability issues too. If, for example, you look at the 458 socom (another "best of breed" design IMO, which, like the 6.8spc had SF guys have a hand in it's development, leading one to believe maybe they do know a thing or two about cartridge designs) you can see the bottom lugs on the extension are "faired" to one smooth ramp for the cartridge to reliably make it into the chamber. Admittedly this is because it's a single stack design; but with not too much work on things like barrel extension, magazine and bolt face designs a whole lot of functional and accuracy issues could be improved upon IMO.

[Nanuk]

As far as the old 30-06... The round used by infantry in WWII used older powders... When the 308 was introduced, due to better powder, the ballistics of the round were pretty close to the old 30-06 stuff.

IMR 4895 I believe is the powder used in the 30-06 from the beginning. It is still a great powder. It propels a 150 grain bullet @ 2900 fps. The 30-30 runs about 2200 fps, not very close.

[Nanuk]

I believe the old target was 60-80lb but the current load is 120-150lb carried into combat actions. Might need to double check those numbers, but I am pretty sure the current load is well over 100lbs.

When I was an Army MP in Germany performing Nuke security and VIP protection details I carried 110 lbs of gear and non of that was food or NOG's or batteries except maybe for the heavy PRC that some poor slob had to carry. I was an M-60 gunner so I had it and a bunch of ammo, an M-16, and a 1911 and lots of ammo for all of them.

[Jim Watson]

IMR 4895 I believe is the powder used in the 30-06 from the beginning.

No, IMR 4895 came out just in time for WWII. There were several other powders used from 1906 til then.

As far as the old 30-06... The round used by infantry in WWII used older powders... When the 308 was introduced, due to better powder, the ballistics of the round were pretty close to the old 30-06 stuff.

Which is kind of amusing, considering the great volume of .308 shot with 4895 and similar powders from the .30-06 era.


I have seen mention of 6.8 SPC II that is supposed to allow somewhat better performance. (I find that it may be like .223-5.56, dimensions fudged to allow heavier loads, higher velocity.)

...if this 6.8 is based on the .30 Remington, I may be wrong, but I think that cartridge originated as competition for the 30-30 Winchester but never rivaled the 30-30 in popularity.

Interesting trivia here; in 1950 Mike Walker at Remington looked at the .30 Remington as the basis for the forthcoming .222. This would have produced something close to a rimless .219 Zipper. He concluded that the basic case was not strong enough for the hotter varmint loads. It is hard to see how that called for a whole new head size production line instead of just beefing up the .30, but that is what they did and we are still living with it.

[JJ45]

Originally Posted by stagpanther

I've done a fair amount of work with the 6.8spc case and wildcats derived from it--the case design is a very good one and if you can push the COL past 2.26--which is very easy to do even within the limits of existing weapons designs--you gain performance by being able to seat longer bullets to a longer COL while gaining additional case capacity for powder. With the 7.62 x 39 I've been able to significantly exceed the 2400 fps using a 125 gr bullet with the right powder and bullet combination, but the case design just isn't going to allow the same flexibility in longer bullets and/or longer COL. IMO it's strength--chamber and go bang every time no matter what no matter who made it or uses it--is also it's weakness in that it allows very little variation and still allow ultra reliability with the world's vast population of AK's. The stubby .310/.311 belly flops ballistically pretty quickly as the range stretches out (still wouldn't want to be hit by one though).

One of the biggest weaknesses I see in the vast majority of "hybrid" AR cartridge design barrels is the functionality of the feed ramps and barrel extension lugs--almost all of which rigidly adhere to the standard M4 type. This is what I attribute a lot of functional reliability issues too. If, for example, you look at the 458 socom (another "best of breed" design IMO, which, like the 6.8spc had SF guys have a hand in it's development, leading one to believe maybe they do know a thing or two about cartridge designs) you can see the bottom lugs on the extension are "faired" to one smooth ramp for the cartridge to reliably make it into the chamber. Admittedly this is because it's a single stack design; but with not too much work on things like barrel extension, magazine and bolt face designs a whole lot of functional and accuracy issues could be improved upon IMO.

The 7.62X39 is supposedly one the best, if not the best, intermediate cartridges for chambering in a SBR... a weapon with a barrel length of from about 8 inches to around 14 inches.

This might simplify the reason ordnance would select the similar 6.8...for use in short barrels for better handling in urban environs, vehicles, etc.

[stagpanther]

The 7.62X39 is supposedly one the best, if not the best, intermediate cartridges for chambering in a SBR... a weapon with a barrel length of from about 8 inches to around 14 inches.

This might simplify the reason ordnance would select the similar 6.8...for use in short barrels for better handling in urban environs, vehicles, etc.

IMO--that's kinda sorta true. The 7.62 x 39 has inspired other modern cartridges--like the Grendel, for example. If you take the case design, maybe straighten out the taper of the main body a bit, knock the shoulder back a bit--presto--you have a 30 Grendel. I have both an AK and an AR47 in 7.62 x 39--I'm very fond of both; but the edge in accuracy I would give to the AR. Unless you're "going off the reservation" with your loads and cartridge dimensions, the 7.62 x 39 in it's present guise is very hard to get around the inherent ballistic limitations of a low SD 30 cal bullet in a smallish cartridge--again, just my opinion. You can take a 6.8 spec case design--load it long up to the limitations of existing AR magwells--which is around 2.36 +/- (the cartridge nose also has to clear the extension edge)--all this is assuming that the new design has some notion of backwards retrofitting to existing weapons--they may in fact have a totally new weapon with totally new upper and lower receiver designs that are not compatible with existing inventory; I have no idea.

[Sharkbite]

The 7.62X39 is supposedly one the best, if not the best, intermediate cartridges for chambering in a SBR... a weapon with a barrel length of from about 8 inches to around 14 inches.

Uhhh No,

The x39 suffers from the same velocity lose out of short barrels as most ctg using “rifle” powders. The king of the hill in SBR performance is 300blackout. That ctg uses magnum pistol powders to get powder burn in the first 6” or so.

It gives x39 ballistics without needing 14+ inches of barrel.

[marine6680]

30-06... I could have not remembered the details correctly... I was reading up on the history of the x51 adoption a good while back, and I remember that the idea was to get similar ballistic performance as the 30-06, but in a smaller overall package. Powder improvement was a factor I remember reading about, and possibly a different bullet weight... It's a bit fuzzy as it was a while ago.


There is a wildcat of 6.8 that is just necked to 6.5, I believe it upped the velocity and BC, and managed to get 2800 using a 110gr bullet.

Drop the weight to 90gr, for extra velocity in a 16in barrel, and you should be close to current 5.56 62gr velocities. Seems a good place to start.

[stagpanther]

Uhhh No,

The x39 suffers from the same velocity lose out of short barrels as most ctg using “rifle” powders. The king of the hill in SBR performance is 300blackout. That ctg uses magnum pistol powders to get powder burn in the first 6” or so.

It gives x39 ballistics without needing 14+ inches of barrel.

Ummm--once again kinda sorta true IMO. I always have thought of the 300BO as a highly efficient pistol cartridge with a rifle bullet for the same reasons you mentioned. But just like the 7.62 x 39--it also uses low SD 30 cal bullets which "run out of gas fast." At 150yds plus I'd MUCH rather have a 7.62 x 39 than a 300BO

[Sharkbite]

Stag,

Take a look at the 150gn Golddot in this caliber. You might be surprised what the 300blk can do. ������

[stagpanther]

Stag,

Take a look at the 150gn Golddot in this caliber. You might be surprised what the 300blk can do. ������

I've had a 300BO pistol for years and love it--so I wouldn't be surprised I've developed some "warmish" loads using the barnes 110 gr TacTx--that bullet really shines in the 300BO and I would use it with confidence against a fair sized target out to 150 yds or so.

[davidsog]

For "making gray matter splatter" at distance, it's hard to beat a 175 grain HPBT and for making bad guys stop bothering you @ 50' a 9mm sub-gun isn't so bad. Problem is finding a platform and cartridge that does both.
I will say that I have absolutely ZERO confidence in 5.56 FMJ of any description. When combining a long, heavy bullet (855--originally meant to punch a hole ) with a short barrel (14.5"), the velocity is too low to induce the destructive tumbling effect or to provide a flat trajectory needed for long range.

I know the guys that initially developed the cartridge and that is exactly what we were looking for....a cartridge that is effective at CQB distances as well as outside the house. It was home grown based lots of experience and arose out of lethality issues with 5.56mm we experience in combat. That ineffectiveness was a hot topic in the team rooms and lingered on everyone's mind that first tour.

It is also one of the results of all the interfacing operators with engineers initiative under George Bush.

I know it was a little over the top about the "Gray Matter..blah blah". It was used to motivate students teaching SMT at SWC. (Infantry Tactics at the Schoolhouse). Forgive me for having a little fun!

[rickyrick]

Drop the weight to 90gr, for extra velocity in a 16in barrel, and you should be close to current 5.56 62gr velocities. Seems a good place to start.

That sounds pretty wicked, something like that in a carbine would peek my interest.

[stagpanther]

Looked at from the logical point of view (at least my logic)--to get a multipurpose cartridge that can "double-duty" for both close CQB and intermediate range sniper/suppression--you need a cartridge that will go "comfortably" up and down between light high BC bullets and heavy big game (guy) droppers Seems to be plenty of .277 offerings between short base bullets and longish higher BC bullets if you can get the COL out there a bit beyond the "default" of 2.26. entirely doable--the only drawback being you're (probably) not going to get just one cartridge load to do both exceedingly well, so there might be some variations in cartridges depending upon use.

Still, there might be some kind of Flash Gordon sci fi new cartridge that will surprise everyone (seems unusually hush hush about what the cartridge design actually is).

[marine6680]

Bottom line is... 5.56 is a great round if you select a good loading. It is plenty lethal for targets in the 200lb range, flat shooting, low recoil, and fits in small lightweight rifles.

For LE and civilian use, you can choose a load to be barrier blind or one that will break apart quickly when hitting barriers... There are many options to get various complementary performance features that you may need.

It does have limitations, and those limitations tend to affect the military more than LE or civilian defensive uses.

Part of the problem is the fact that the military is limited on the types of bullets it can use legally on a battlefield. The increased need to be able to punch through light armor and barriers like block walls or metal doors or any number of things is not a 5.56 strong suit. FMJ is a poor stopper... Some new ammo has helped with that, but also has trade offs. The new m855a1 is said to be a fantastic all around loading, but is pushing the rifle to the limit with it's extremely high chamber pressure.

Short barrel performance is also lacking, which affects everyone who needs such things. For LE and civilian use, being very picky about ammo choice can mitigate the problem, but testing the ammo performance is very important to know if the ammo is working for ypu. In such a case.


Bumping up the caliber a bit, but not to a full 30cal, and keeping speed close to current speeds will get you what you could want, but design will still be important. A careful balancing act to get the most of the things you need.

[Mobuck]

"for both close CQB and intermediate range sniper/suppression--you need a cartridge that will go "comfortably" up and down between light high BC bullets and heavy big game (guy) droppers"
"you can choose a load to be barrier blind or one that will break apart quickly when hitting barriers... There are many options to get various complementary performance features that you may need."

And this is the problem with military use. I( or you) can quite easily have several choices of ammo loaded up ready to go for various purposes.
One problem with this is maintaining zero for several bullet weights/types in an "on the go" situation.
Another is the fact that to some(many) troops, "bullets is bullets" and training those troops to swap out ammo to meet specific needs is far too complicated especially under combat conditions.

[stagpanther]

And this is the problem with military use. I( or you) can quite easily have several choices of ammo loaded up ready to go for various purposes.
One problem with this is maintaining zero for several bullet weights/types in an "on the go" situation.
Another is the fact that to some(many) troops, "bullets is bullets" and training those troops to swap out ammo to meet specific needs is far too complicated especially under combat conditions.

Good point(s)--though it seems to make more sense to me to vary the bullet types than to develop a whole new weapon system around each cartridge.

[HiBC]

My understanding :The 300 Blackout was developed by J D Jones as a cartridge to fling heavy,high ballistic coefficient 30 cal bullets at subsonic muzzle velocities.

It was designed for very quiet suppressor work with the AR platform.

[davidsog]

Looked at from the logical point of view (at least my logic)--to get a multipurpose cartridge that can "double-duty" for both close CQB and intermediate range sniper/suppression--you need a cartridge that will go "comfortably" up and down between light high BC bullets and heavy big game (guy) droppers Seems to be plenty of .277 offerings between short base bullets and longish higher BC bullets if you can get the COL out there a bit beyond the "default" of 2.26. entirely doable--the only drawback being you're (probably) not going to get just one cartridge load to do both exceedingly well, so there might be some variations in cartridges depending upon use.

You do realize there are some 45 different kinds of 7.62MM Nato in the inventory???

There is a reason why the DoD small arms data book is ~3 inches thick.

[davidsog]

And this is the problem with military use. I( or you) can quite easily have several choices of ammo loaded up ready to go for various purposes.

So you are going to change rounds in the middle of the fight? Or run to the closet to select a different ammo type??