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Posted: 8/3/2007 2:45:53 AM EDT
Has anyone played around with these?
I'd be interested in knowing your findings.
thanks
Link Posted: 8/3/2007 3:45:42 AM EDT
Sure, there have been attempts.

However, if you look at the old .30 Remington case, you will quickly see all the limitations inherent to a cartridge which must have OAL of around 2.3" to fit in a standard AR mag well.

Once you have COAL limits like that, bullets in the 6, 6.5, 6.8, 7mm range become compromises. Trying to get something with a good BC has been difficult and the larger caliber you attempt, the longer the bullets get, generally speaking. If you go long to get more BC, you trade off case capacity and many of the hot loads have to be compressed as it is. The longer loads also dictate which chamber / throat might still allow feeding and accuracy, while not raising pressure.

The 6.8 SPC. is the one for which you can simply go out an buy a rifle and factory ammo. There are no other SPC's in production and the Grendel is a completely different design. Great for its purposes, but just not worth comparing as regards your question.

Once we start playing with 7mm, the problems in developing the load just get tougher. There might be a little better selection of 7mm bullets, but not many < 120 grains, and that is where the weights for .277 and .284 caliber SPC's are going to need to be to suit the demands.

In fact, one of the best handloads coming out right now is a 90-grain Speer TNT with H322, in 6.8 SPC. With the proper 1 in 11" twist, 4 groove rifling, and chamber length, it is being loaded to 2800 FPS in a 16" barrel.

I say we develop the 6.8 SPC, get better bullets and powder made to suit the compromise and forget 6, 6.5, 7 or 7.62 MM SPC for now. JMHO, YMMV
Link Posted: 8/3/2007 5:40:21 AM EDT
[Last Edit: 8/3/2007 5:58:27 AM EDT by constructor]
Nice reply and dead on IMO. I do not think going larger is the way to go for long range development.
If you like wildcats. The new .223SPC and 6mmWOA may be good long range or highpower choices. Contact John Holliger at WOA.
My 30 HRT should be here next week. It is specifically to make MPF for 3 gun 350yds and under.
Link Posted: 8/3/2007 6:03:09 AM EDT
BadShot, I haven't played around with a 7mm Grendel, but the concept is sound. In theory, the Grendel case at 39mm can easily handle the ogive length of even the heaviest 7mm bullets, so fitting them in the case within magazine-length limitations shouldn't be a problem. As mentiioned above, though, you're impinging on case capacity with the heavier projectiles.

However, most 7mm 140-grain bullets will probably be of similar length to most 6.5mm 120-grain bullets, so even in that instance your case impingement is somewhat mitigated.

A 7mm Grendel with the heavy 140-class bullets would be a very nice thumper for brush-hunting tough game, however, you'd have to accept the trade-off in long-range trajectory.

I believe it was Dr. Roberts who reported that something like a 120- or 125-grain 7mm bullet had the best terminal ballistics when developing the 6.8 SPC. So a 7mm Grendel launching that same bullet even faster would be an awesome "tactical varmint" round.

John

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |
Link Posted: 8/3/2007 7:31:18 AM EDT
[Last Edit: 8/3/2007 7:31:42 AM EDT by paulosantos]

Originally Posted By Grendelizor:
BadShot, I haven't played around with a 7mm Grendel, but the concept is sound. In theory, the Grendel case at 39mm can easily handle the ogive length of even the heaviest 7mm bullets, so fitting them in the case within magazine-length limitations shouldn't be a problem. As mentiioned above, though, you're impinging on case capacity with the heavier projectiles.

However, most 7mm 140-grain bullets will probably be of similar length to most 6.5mm 120-grain bullets, so even in that instance your case impingement is somewhat mitigated.

A 7mm Grendel with the heavy 140-class bullets would be a very nice thumper for brush-hunting tough game, however, you'd have to accept the trade-off in long-range trajectory.

I believe it was Dr. Roberts who reported that something like a 120- or 125-grain 7mm bullet had the best terminal ballistics when developing the 6.8 SPC. So a 7mm Grendel launching that same bullet even faster would be an awesome "tactical varmint" round.

John

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |


I like your original Tag-Line better.

I think the 6.8SPC is just about the ideal round for the AR-15. The problem is the lack of good bullets in the 90-100 Gr. range. The 6.8SPC was designed as a short to Medium range round. If you want a long distance round, look into the 6.5Grendel.
Link Posted: 8/3/2007 7:48:15 AM EDT

Originally Posted By paulosantos: The 6.8SPC was designed as a short to Medium range round. If you want a long distance round, look into the 6.5Grendel.


If you want a short to medium range round, look into the 6.5 Grendel.

John

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |
Link Posted: 8/3/2007 8:14:48 AM EDT
John, After the first post I thought you had turned over a new leaf
Link Posted: 8/3/2007 8:43:55 AM EDT
[Last Edit: 8/3/2007 8:45:06 AM EDT by Grendelizor]

Originally Posted By constructor: John, After the first post I thought you had turned over a new leaf


You mean in the sense of abandoning the 6.5 Grendel in favor of a 7.0 Grendel? Hmmm. . . . I wouldn't complain too much.

What you need to realize is that I'm more wedded to the CONCEPT than the particular caliber. I'm convinced that if you limit yourself to an intermediate case, such as to be used at mag-length in an AR and within the existing bolt-diameter constraints, then you absolutely must allow for longer, high BC bullets that can rely more on momentum than initial muzzle velocity for their performance envelope.

Now, it happens to be my personal belief that since the 6.5mm caliber lies exactly between the spectrum extremes of .22 and .30, that the 6.5 Grendel is the optimum balance of bullet mass, recoil, and trajectory for the AR platform.

Having said that, if the creators of the 6.8 SPC had had the foresight to create a "6.8" Grendel,* my Website would probably have a different name!

John

*But they didn't, because they didn't believe the engineering could be made to work. I guess they didn't ask Bill Alexander. . . .

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |
Link Posted: 8/3/2007 9:19:14 AM EDT

Originally Posted By Grendelizor:

Originally Posted By paulosantos: The 6.8SPC was designed as a short to Medium range round. If you want a long distance round, look into the 6.5Grendel.


If you want a short to medium range round, look into the 6.5 Grendel.

John

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |


You may want to look into getting some extra bolts while you are looking into the 6.5 Grendel. Sorry, I had to say it. You are too easy to mess with John.
Link Posted: 8/3/2007 9:30:05 AM EDT

Originally Posted By paulosantos: You may want to look into getting some extra bolts while you are looking into the 6.5 Grendel. Sorry, I had to say it. You are too easy to mess with John.


Kind of a low blow, dude! But, hey, it's Friday, so I'm chillin'. . . .

John

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |
Link Posted: 8/3/2007 9:30:14 AM EDT

Originally Posted By paulosantos:

Originally Posted By Grendelizor:

Originally Posted By paulosantos: The 6.8SPC was designed as a short to Medium range round. If you want a long distance round, look into the 6.5Grendel.


If you want a short to medium range round, look into the 6.5 Grendel.

John

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |


You may want to look into getting some extra bolts while you are looking into the 6.5 Grendel. Sorry, I had to say it. You are too easy to mess with John.



He beat me to it......I was going to say "...uh, from what we hear about bolts when the round gets pushed, maybe they were right! " But, I couldn't bring myself to start the shitstorm......AAAHHHHH!

Please don't let's make this a 6.8 versus 6.5 Grendel thread .....I promise I won't if everyone else won't.....
Link Posted: 8/3/2007 9:33:48 AM EDT
John I agree on the concept. Thats why I'm doing the 6.5 Reaper on an AR10 platform. How does the 139 Lapua at 3000fps sound?
Link Posted: 8/3/2007 9:36:16 AM EDT

Originally Posted By Grendelizor:

Originally Posted By paulosantos: You may want to look into getting some extra bolts while you are looking into the 6.5 Grendel. Sorry, I had to say it. You are too easy to mess with John.


Kind of a low blow, dude! But, hey, it's Friday, so I'm chillin'. . . .

John

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |


I'm sorry John. Just having fun. Keep Chillin"
Link Posted: 8/3/2007 10:08:53 AM EDT
Same here, dude, just messin' with ya'.....
Link Posted: 8/3/2007 10:30:14 AM EDT
If you think about it the 6.8 is pretty damn close to being a 7mm to start with. With that said, when you take a case and neck it up in caliber it gains the ability to throw heavier bullets without as much pressure then if the heavier bullet was in the original caliber and case. Here is a classic example. Shooting very heavy bullet from the 30-06. I'm talking over 200 grains and especially 250 grains or higher. When necking up the 06 case to 35 caliber, such as the 35 Whelen, it throws the heavier bullets with less pressure and in many cases even faster.

I don't think that there would be much difference in a 7mm/6.8, except a totally different selection of bullets. In my opinion there would be more of a difference in a 7mm/6.5.

I also disagree with going bigger isn't the way go because looks at the round that really started the "assault rifle cartridges", the 7.92 Kurtz and the 7.62x39. Both good rounds in my opinion. Now if the original intent is to increase long distance...then I say no...not with the two cases mentioned.

Being the Grendel can deliver more then the AR can handle, at the moment, I don't see any advantage to necking it down to 6mm or 22 cal when two cartridges exist in those calibers that are too close to the Grendel...the PPC's.
Link Posted: 8/3/2007 10:43:40 AM EDT

Originally Posted By Grendelizor: In theory, the Grendel case at 39mm can easily handle the ogive length of even the heaviest 7mm bullets, so fitting them in the case within magazine-length limitations shouldn't be a problem. |



No way dude, have you ever even looked at a 180 gr 7mm Berger? It can't even efficently handle the long heavy 6.5s. M9
Link Posted: 8/3/2007 11:12:37 AM EDT

Originally Posted By JFA:
If you think about it the 6.8 is pretty damn close to being a 7mm to start with. With that said, when you take a case and neck it up in caliber it gains the ability to throw heavier bullets without as much pressure then if the heavier bullet was in the original caliber and case. Here is a classic example. Shooting very heavy bullet from the 30-06. I'm talking over 200 grains and especially 250 grains or higher. When necking up the 06 case to 35 caliber, such as the 35 Whelen, it throws the heavier bullets with less pressure and in many cases even faster.

I don't think that there would be much difference in a 7mm/6.8, except a totally different selection of bullets. In my opinion there would be more of a difference in a 7mm/6.5.

I also disagree with going bigger isn't the way go because looks at the round that really started the "assault rifle cartridges", the 7.92 Kurtz and the 7.62x39. Both good rounds in my opinion. Now if the original intent is to increase long distance...then I say no...not with the two cases mentioned.

Being the Grendel can deliver more then the AR can handle, at the moment, I don't see any advantage to necking it down to 6mm or 22 cal when two cartridges exist in those calibers that are too close to the Grendel...the PPC's
.



Which makes my point exactly: the AR can handle the hottest incarnation of the 6.8 SPC right now, given that the specs are to a certain design....one now currently , easiiy available at a very reasonable price (Ko-Tonics, etc). So, why would we need to start over with any of these others? Once the Grendel is more widely avaialble, we'll just have more choices.

Now that we are seeing the 6.8, in 90-100-110 and 120 grain bullets clocking 2700-2800 FPS out of a 16" barrel....then, you have just about the ideal AR cartridge whcih can fit into the AR-15 magwell and be so easily converted and cross-mutated with existing accessories.

Things look pretty good for the future....
Link Posted: 8/3/2007 12:17:39 PM EDT
As has been stated multiple times, the designers of the SPC started off using 6 mm PPC/6.5 mm PPC cases as their starting point. After testing these, they switched to a .30 Remington parent case, as the PPC cases were not as reliable in the AR15/M4 format. The 7 mm SPC variant offered outstanding terminal performance, but were not as accurate as the 6.5 mm SPC and 6.8 mm SPC. The 6.8 mm was the best compromise of accuracy, terminal performance, and reliability.

----------------------------------------------------

While the 6.8 mm has repeatedly demonstrated outstanding terminal performance in JSWB-IPT testing, FBI BRF testing, and USMC testing, keep in mind that the 6.8 mm design is a compromise that does not maximize assault rifle terminal performance, as it is constrained by the requirement to fit and function in the 5.56 mm M4/M16 magazine. The 6.5 mm Grendel is inhibited by this same limitation, with the added deficit of using the weak 7.62 x 39 mm AR15 bolt design that has a history of premature failure.

Fortunately, while at USAMU, Cris Murray, one of the co-designers of the 6.8 mm SPC simultaneously developed an “ideal” assault rifle cartridge, with none of the platform imposed design compromises that limit both the 6.5 mm Grendel and 6.8 mm SPC. This “idealized” assault rifle cartridge, the 7 x 46 mm, offers better range and terminal performance than 6.5 mm Grendel, 6.8 mm SPC, or any other common assault rifle cartridges, including 5.45 x 39 mm, 5.56 x 45 mm and 7.62 x 39 mm. Since the 7 x 46 mm is based on the proven Czech military 7.62 x 45 mm cartridge, it has an established record feeding and functioning in both magazine and belt-fed full-auto fire. Likewise, recoil appears manageable and weapons remain controllable in FA fire, just as with the Czech cartridge. In addition, the 7 x 46 mm is optimized for shorter barrels and larger magazines than the heavier, bulkier, and harsher recoiling 7.62 x 51 mm/.308 cartridge. The 7 x 46 mm is truly the best assault rifle cartridge developed to date.

The main problem is that the 7 x 46 mm cartridge OAL is a bit too long to fit into the M4/M16 or other 5.56 mm size weapons/magazines, yet it does not need a receiver/magazine as large as those used by 7.62 x 51 mm/.308 platforms such as the M14, Mk11, M110. As a result, the 7 x 46 mm requires new weapons--envision a rifle sized a bit larger than the AR15, but small than an AR10/SR25. These new weapons would shoot 7 mm bullets of 120-140 gr at 2800-2900 f/s. The 7 x 46 mm also offers amazing long range accuracy when using heavier, high BC bullets like the 7 mm 175 gr SMK… The only similar cartridge is the new Lapua 6.5 x 47 mm, however, the 6.5 x 47 mm was designed for civilian match shooting and to date, has only been used in precision bolt action rifles and not in any semi-auto or full-auto military weapons.

Bottom line:

-- 6.8 mm SPC is the best available solution to upgrade current 5.56 mm weapons.

-- If given a clean slate of paper and substantial development funds, the clear and obvious best cartridge for new design weapons is the 7 x 46 mm, as it offers greater soft tissue terminal performance, better intermediate barrier penetration, and greater maximum range and long distance performance than traditional assault rifle cartridges like the 5.45 x 39 mm, 5.56 mm, 7.62 x 39 mm, as well as the newer 6.5 mm Grendel and 6.8 mm SPC.
Link Posted: 8/3/2007 12:24:21 PM EDT

Originally Posted By DocGKR:
As has been stated multiple times, the designers of the SPC started off using 6 mm PPC/6.5 mm PPC cases as their starting point. After testing these, they switched to a .30 Remington parent case, as the PPC cases were not as reliable in the AR15/M4 format. The 7 mm SPC variant offered outstanding terminal performance, but were not as accurate as the 6.5 mm SPC and 6.8 mm SPC. The 6.8 mm was the best compromise of accuracy, terminal performance, and reliability.

----------------------------------------------------

While the 6.8 mm has repeatedly demonstrated outstanding terminal performance in JSWB-IPT testing, FBI BRF testing, and USMC testing, keep in mind that the 6.8 mm design is a compromise that does not maximize assault rifle terminal performance, as it is constrained by the requirement to fit and function in the 5.56 mm M4/M16 magazine. The 6.5 mm Grendel is inhibited by this same limitation, with the added deficit of using the weak 7.62 x 39 mm AR15 bolt design that has a history of premature failure.

Fortunately, while at USAMU, Cris Murray, one of the co-designers of the 6.8 mm SPC simultaneously developed an “ideal” assault rifle cartridge, with none of the platform imposed design compromises that limit both the 6.5 mm Grendel and 6.8 mm SPC. This “idealized” assault rifle cartridge, the 7 x 46 mm, offers better range and terminal performance than 6.5 mm Grendel, 6.8 mm SPC, or any other common assault rifle cartridges, including 5.45 x 39 mm, 5.56 x 45 mm and 7.62 x 39 mm. Since the 7 x 46 mm is based on the proven Czech military 7.62 x 45 mm cartridge, it has an established record feeding and functioning in both magazine and belt-fed full-auto fire. Likewise, recoil appears manageable and weapons remain controllable in FA fire, just as with the Czech cartridge. In addition, the 7 x 46 mm is optimized for shorter barrels and larger magazines than the heavier, bulkier, and harsher recoiling 7.62 x 51 mm/.308 cartridge. The 7 x 46 mm is truly the best assault rifle cartridge developed to date.

The main problem is that the 7 x 46 mm cartridge OAL is a bit too long to fit into the M4/M16 or other 5.56 mm size weapons/magazines, yet it does not need a receiver/magazine as large as those used by 7.62 x 51 mm/.308 platforms such as the M14, Mk11, M110. As a result, the 7 x 46 mm requires new weapons--envision a rifle sized a bit larger than the AR15, but small than an AR10/SR25. These new weapons would shoot 7 mm bullets of 120-140 gr at 2800-2900 f/s. The 7 x 46 mm also offers amazing long range accuracy when using heavier, high BC bullets like the 7 mm 175 gr SMK… The only similar cartridge is the new Lapua 6.5 x 47 mm, however, the 6.5 x 47 mm was designed for civilian match shooting and to date, has only been used in precision bolt action rifles and not in any semi-auto or full-auto military weapons.

Bottom line:

-- 6.8 mm SPC is the best available solution to upgrade current 5.56 mm weapons.

-- If given a clean slate of paper and substantial development funds, the clear and obvious best cartridge for new design weapons is the 7 x 46 mm, as it offers greater soft tissue terminal performance, better intermediate barrier penetration, and greater maximum range and long distance performance than traditional assault rifle cartridges like the 5.45 x 39 mm, 5.56 mm, 7.62 x 39 mm, as well as the newer 6.5 mm Grendel and 6.8 mm SPC.



Now we're talkin. That DOES sound good. I've always been a fan of 7mm's as most my big games rifles are in one or another of the 7mm's.

Now if we can shoehorn that 7x46 into an AR format, which components that will take more then the round can dish out...I'll be happier.
Link Posted: 8/3/2007 12:49:42 PM EDT

Originally Posted By DocGKR:
As has been stated multiple times, the designers of the SPC started off using 6 mm PPC/6.5 mm PPC cases as their starting point. After testing these, they switched to a .30 Remington parent case, as the PPC cases were not as reliable in the AR15/M4 format. The 7 mm SPC variant offered outstanding terminal performance, but were not as accurate as the 6.5 mm SPC and 6.8 mm SPC. The 6.8 mm was the best compromise of accuracy, terminal performance, and reliability.

----------------------------------------------------

While the 6.8 mm has repeatedly demonstrated outstanding terminal performance in JSWB-IPT testing, FBI BRF testing, and USMC testing, keep in mind that the 6.8 mm design is a compromise that does not maximize assault rifle terminal performance, as it is constrained by the requirement to fit and function in the 5.56 mm M4/M16 magazine. The 6.5 mm Grendel is inhibited by this same limitation, with the added deficit of using the weak 7.62 x 39 mm AR15 bolt design that has a history of premature failure.

Fortunately, while at USAMU, Cris Murray, one of the co-designers of the 6.8 mm SPC simultaneously developed an “ideal” assault rifle cartridge, with none of the platform imposed design compromises that limit both the 6.5 mm Grendel and 6.8 mm SPC. This “idealized” assault rifle cartridge, the 7 x 46 mm, offers better range and terminal performance than 6.5 mm Grendel, 6.8 mm SPC, or any other common assault rifle cartridges, including 5.45 x 39 mm, 5.56 x 45 mm and 7.62 x 39 mm. Since the 7 x 46 mm is based on the proven Czech military 7.62 x 45 mm cartridge, it has an established record feeding and functioning in both magazine and belt-fed full-auto fire. Likewise, recoil appears manageable and weapons remain controllable in FA fire, just as with the Czech cartridge. In addition, the 7 x 46 mm is optimized for shorter barrels and larger magazines than the heavier, bulkier, and harsher recoiling 7.62 x 51 mm/.308 cartridge. The 7 x 46 mm is truly the best assault rifle cartridge developed to date.

The main problem is that the 7 x 46 mm cartridge OAL is a bit too long to fit into the M4/M16 or other 5.56 mm size weapons/magazines, yet it does not need a receiver/magazine as large as those used by 7.62 x 51 mm/.308 platforms such as the M14, Mk11, M110. As a result, the 7 x 46 mm requires new weapons--envision a rifle sized a bit larger than the AR15, but small than an AR10/SR25. These new weapons would shoot 7 mm bullets of 120-140 gr at 2800-2900 f/s. The 7 x 46 mm also offers amazing long range accuracy when using heavier, high BC bullets like the 7 mm 175 gr SMK… The only similar cartridge is the new Lapua 6.5 x 47 mm, however, the 6.5 x 47 mm was designed for civilian match shooting and to date, has only been used in precision bolt action rifles and not in any semi-auto or full-auto military weapons.

Bottom line:

-- 6.8 mm SPC is the best available solution to upgrade current 5.56 mm weapons.

-- If given a clean slate of paper and substantial development funds, the clear and obvious best cartridge for new design weapons is the 7 x 46 mm, as it offers greater soft tissue terminal performance, better intermediate barrier penetration, and greater maximum range and long distance performance than traditional assault rifle cartridges like the 5.45 x 39 mm, 5.56 mm, 7.62 x 39 mm, as well as the newer 6.5 mm Grendel and 6.8 mm SPC.




Thanks for the great info Doc..... I am also confident that you might join us in the quest for the "new" powders and bullets we need to fully optimize the 6.8 SPC. Just a little different burn rate, a little better BC and the right barrel dimensions and we are off to the races for the next 10 years.



I hope the newbs are tagging this thread!

Link Posted: 8/3/2007 2:01:00 PM EDT
[Last Edit: 8/3/2007 2:06:06 PM EDT by Grendelizor]

Originally Posted By DocGKR: As has been stated multiple times, the designers of the SPC started off using 6 mm PPC/6.5 mm PPC cases as their starting point. After testing these, they switched to a .30 Remington parent case, as the PPC cases were not as reliable in the AR15/M4 format.


That was then, this is now. They did not test the 6.5 Grendel, with its shorter neck, modified feed ramp angle, and, most importantly, dedicated 6.5 Grendel AR magazines.


Originally Posted By DocGKR: The 6.5 mm Grendel is inhibited by this same limitation, with the added deficit of using the weak 7.62 x 39 mm AR15 bolt design that has a history of premature failure.


Incorrect. Bill Alexander does not certify the current standard of off-the-shelf 7.62x39 AR15 bolts as qualified for use in the 6.5 Grendel. He only uses, in both Beowulf and Grendel products, a bolt modified and certified for this application.

Thus, the charge of "weak 7.62x39" bolts does not apply to the 6.5 Grendel. Even more ironic is that it was Bill Alexander who, in a firestorm of controversy, first decried their use.


Originally Posted By DocGKR: The 7 x 46 mm is truly the best assault rifle cartridge developed to date.


I disagree. While the 7x46 cartridge sounds great, I definitely would not classify it as an assault rifle cartridge, but as what is referred to as a "battle rifle" cartridge.

When designing from a clean slate, any decision regarding cartridge overall length is arbitrary depending on the performance one seeks, but I think there is value in keeping the cartridge as compact as possible. The overall length of 5.56 NATO, as it turns out, represents the longest I would go in an assault rifle cartridge in order to keep recoil forces, ammunition bulk, and weapon size to a minimum.


Originally Posted By DocGKR: The 7 x 46 mm also offers amazing long range accuracy when using heavier, high BC bullets like the 7 mm 175 gr SMK. . . . the clear and obvious best cartridge for new design weapons is the 7 x 46 mm, as it offers greater soft tissue terminal performance, better intermediate barrier penetration, and greater maximum range and long distance performance than traditional assault rifle cartridges


We have been told over and over and over again that assault rifle cartridges do not need, indeed, should not be forced to have long-range performance. This is either a major sea-change in your thinking or a stunning double-standard after all the abuse the 6.5 Grendel has taken for simply being a compact assault rifle cartridge with the added benefit of very good long-range performance.


Originally Posted By DocGKR: Bottom line: 6.8 mm SPC is the best available solution to upgrade current 5.56 mm weapons.


Obviously, quite wrong.

John

P.S. I'm still amazed, after all the criticism leveled at the 6.5 Grendel, that you are now touting an "assault rifle" cartridge distinguished, almost exclusively, for its long-range capability. This about-face is incredible, actually. . . .

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |
Link Posted: 8/3/2007 2:12:56 PM EDT

Originally Posted By Grendelizor:

Originally Posted By DocGKR: As has been stated multiple times, the designers of the SPC started off using 6 mm PPC/6.5 mm PPC cases as their starting point. After testing these, they switched to a .30 Remington parent case, as the PPC cases were not as reliable in the AR15/M4 format.


That was then, this is now. They did not test the 6.5 Grendel, with its shorter neck, modified feed ramp angle, and, most importantly, dedicated 6.5 Grendel AR magazines.


Originally Posted By DocGKR: The 6.5 mm Grendel is inhibited by this same limitation, with the added deficit of using the weak 7.62 x 39 mm AR15 bolt design that has a history of premature failure.


Incorrect. Bill Alexander does not certify the current standard of off-the-shelf 7.62x39 AR15 bolts as qualified for use in the 6.5 Grendel. He only uses, in both Beowulf and Grendel products, a bolt modified and certified for this application.

Thus, the charge of "weak 7.62x39" bolts does not apply to the 6.5 Grendel. Even more ironic is that it was Bill Alexander who, in a firestorm of controversy, first decried their use.


Originally Posted By DocGKR: The 7 x 46 mm is truly the best assault rifle cartridge developed to date.


I disagree. While the 7x46 cartridge sounds great, I definitely would not classify it as an assault rifle cartridge, but as what is referred to as a "battle rifle" cartridge.

When designing from a clean slate, any decision regarding cartridge overall length is arbitrary depending on the performance one seeks, but I think there is value in keeping the cartridge as compact as possible. The overall length of 5.56 NATO, as it turns out, represents the longest I would go in an assault rifle cartridge in order to keep recoil forces, ammunition bulk, and weapon size to a minimum.


Originally Posted By DocGKR: The 7 x 46 mm also offers amazing long range accuracy when using heavier, high BC bullets like the 7 mm 175 gr SMK. . . . the clear and obvious best cartridge for new design weapons is the 7 x 46 mm, as it offers greater soft tissue terminal performance, better intermediate barrier penetration, and greater maximum range and long distance performance than traditional assault rifle cartridges


We have been told over and over and over again that assault rifle cartridges do not need, indeed, should not be forced to have long-range performance. This is either a major sea-change in your thinking or a stunning double-standard after all the abuse the 6.5 Grendel has taken for simply being a compact assault rifle cartridge with the added benefit of very good long-range performance.


Originally Posted By DocGKR: Bottom line: 6.8 mm SPC is the best available solution to upgrade current 5.56 mm weapons.


Obviously, quite wrong.

John

P.S. I'm still amazed, after all the criticism leveled at the 6.5 Grendel, that you are now touting an "assault rifle" cartridge distinguished, almost exclusively, for its long-range capability. Incredible, actually. . . .

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |


John, I think the sun is getting to you. I don't see any double standards in Doc's post. You are not reading it correctly. The way I interpeted it was that the new cartridge is flexible enough that it can be used as both a standard assault cartridge and still has enough capacity that it can also be used as a long range cartridge with the heavier bullets with the high BC. The 6.8SPC and 6.5Grendel just don't have the capacity to do both since there isn't enough powder capacity to make it a good long range cartridge.

This of course is just my opinion and I am not putting any words in Doc's mouth.
Link Posted: 8/3/2007 2:25:40 PM EDT
OST. This is going to get interesting.
Link Posted: 8/3/2007 2:49:32 PM EDT

Originally Posted By Combat_Jack:
OST. This is going to get interesting.



Ok, turning, running......I'm not going to touch this one with a 10-foot pole.......
Link Posted: 8/3/2007 3:49:25 PM EDT
Let's see, the Czech 7.62 x 45 mm M52 is classified as an ASSAULT RIFLE cartridge; since the new 7 x 46 mm is based on the M52 ASSAULT RIFLE cartridge, it follows logically that the 7 x 46 mm is also clearly defined as an ASSAULT RIFLE cartridge.
Link Posted: 8/3/2007 4:21:41 PM EDT
[Last Edit: 8/3/2007 4:31:04 PM EDT by Grendelizor]

Originally Posted By DocGKR: Let's see, the Czech 7.62 x 45 mm M52 is classified as an ASSAULT RIFLE cartridge; since the new 7 x 46 mm is based on the M52 ASSAULT RIFLE cartridge, it follows logically that the 7 x 46 mm is also clearly defined as an ASSAULT RIFLE cartridge.


OK, I'm willing to assume I misunderstood you. When I think of the 7.62x45 Czech, I think of a very stubby bullet with a BC probably worse than 7.62x39 Russian. When I think of some of the other 7mm combat cartridges proposed from the 1950s, I think of long, high BC bullets. Which does the 7x46 propose to use? You mentioned a range from 120-140, and also 175gr SMK, hence my confusion.

See Anthony Williams' informative site here for plenty of photos.

To fully understand the 7x46 concept, we'd need to know what is the cartridge's overall length?

When you say it's similar to the new 6.5 x 47 Lapua, I automatically think "battle rifle" because that cartridge, at least, shares the same OAL as 7.62x51 NATO.

John

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |
Link Posted: 8/3/2007 4:27:31 PM EDT
Uh...that information was already provided above:

"These new weapons would shoot 7 mm bullets of 120-140 gr at 2800-2900 f/s.
Link Posted: 8/3/2007 4:53:44 PM EDT
Once again, someone is trying to make the AR15 into something it is not!

The 6.8 and 6.5 are about as maxed out as the platform can be, now we are talking about a 7mm bullet!

I don't disagree that there COULD be a better assault rifle cartridge, but it's going to need to come in a better package than anything currently out there. The 6.8 and 6.5 push the max OAL as it is. There has to be a better way! There is, but the US military is decades away from accepting a new rifle.

Now, if MagPul can pull off this cartridge in their new platform, the Masada, then we would all have a new toy, but the military isn't going that route, at least in the near term.

But for too many couch commandos, the AR15 platform is the be all and end all, regardless of whether there actually IS a better weapon! As I heard a couple soldiers say when someone said that there are better sniper rounds than the .308, "The .308 is the BEST, if it wasn't Uncle Sam would tell us and buy it!"

Bill
Link Posted: 8/3/2007 5:13:56 PM EDT

Originally Posted By DocGKR: Uh...that information was already provided above


Yes, I apologize for asking about something you already mentioned, if I had only read more closely.

But I don't believe you mentioned what is the overall length, other than something more than 5.56 and less than 7.62. What is the exact OAL?

John

| 6.5 Grendel: The State-of-the-Art Combat Cartridge. |
Link Posted: 8/3/2007 5:21:10 PM EDT
IIRC around 2.5".
Link Posted: 8/3/2007 5:58:00 PM EDT
[Last Edit: 8/3/2007 6:13:41 PM EDT by M9Powell]

Originally Posted By DocGKR:
While the 6.8 mm has repeatedly demonstrated outstanding terminal performance in JSWB-IPT testing, FBI BRF testing, and USMC testing, keep in mind that the 6.8 mm design is a compromise that does not maximize assault rifle terminal performance, as it is constrained by the requirement to fit and function in the 5.56 mm M4/M16 magazine. The 6.5 mm Grendel is inhibited by this same limitation, with the added deficit of using the weak 7.62 x 39 mm AR15 bolt design that has a history of premature failure.


I completly agree with the Doc on the above, but on the 7X46, I'm sorry, but I think he is too tightly focused on terminal ballistics. Any ctg that has more recoil than 7.62X39 isn't going to cut it as an assault rifle ctg. An assault rifle is by it's very nature selective fire. It's an extended range submachine gun. An M16A1 is an assault rifle that is barely controllable. Heck an M2 carbine is barely controllable. There is no point in trying to combine the best features of the assault rifle & the battle rifle, it won't work. Pick your poison. The only way a more potent ctg would be controllable would be in a heavy rifle think 12 lbs +. You can't have your cake & eat it too. If you want the ideal assault rifle ctg, its going to be something like 8mm Kurtz necked to 7mm with light bullets. Thats what the original designers wanted, but were forced to use existing barrel making tooling. M9

PS If you want the best assault rifle ctg that will fit in an AR15, I'd suggest the triple duece necked to 6mm with light bullets. If you want the best semi carbine ctg for CQB in an AR, then 6.8 SPC is going to be hard to beat.
Link Posted: 8/3/2007 6:15:08 PM EDT
To clarify something, Doc never said "an off the shelf 7.6x39 bolt". He said "7.62 x 39 mm AR15 bolt design". To me that would include all bolts that have bolt face recess to accept a 7.62x39 size case.
Link Posted: 8/3/2007 6:19:13 PM EDT
[Last Edit: 8/3/2007 6:35:43 PM EDT by M9Powell]

Originally Posted By JFA:
To clarify something, Doc never said "an off the shelf 7.6x39 bolt". He said "7.62 x 39 mm AR15 bolt design". To me that would include all bolts that have bolt face recess to accept a 7.62x39 size case.


It looks like a duck, it quakes like a duck, it costs like a duck & it cracks like a duck, must be a duck. If it wants to prove it ain't a duck the DNA test is 70,000 PSI on each upper, weapon or bolt. M9
Link Posted: 8/3/2007 6:55:17 PM EDT
Link Posted: 8/3/2007 7:59:26 PM EDT

Originally Posted By Forest:

Originally Posted By constructor:
John I agree on the concept. Thats why I'm doing the 6.5 Reaper on an AR10 platform. How does the 139 Lapua at 3000fps sound?


Dude you have to stop posting stuff like this.

It gives me ideas about buying expensive rifles I really don't need...


Control yourself Forest. I have all the control i need. It is called a wife.
Link Posted: 8/3/2007 8:04:35 PM EDT
Link Posted: 8/3/2007 8:29:10 PM EDT
height=8
Originally Posted By DocGKR:
The 6.5 mm Grendel is inhibited by this same limitation, with the added deficit of using the weak 7.62 x 39 mm AR15 bolt design that has a history of premature failure.


Doctor Roberts,

The statement quoted above is rather open ended, and I cannot discern whether the deficit you are referring to is one of reputation, solid mechanics, or QA for the end product.

I have little impact on the issues of reputation or QA of an end product.

A solid mechanics deficit is readily surpassed in material selection. There are many newer alloys superior to Carpenter 158 for this bolt application; advantages realized most at temperatures above 750 F. Bill Alexander has offered some clues as to what alloy he has selected, but he does not want me championing this cause. I cannot fault his position; I would not want a stranger representing a design of my own.

Your statement was brief, and I will keep my response brief. You have been forthcoming with your background and credentials. If my credentials are required to participate, let me know. I live in the identity theft capitol of the world for 2006, and will keep my cards close to my chest when I can.

Matt M
Link Posted: 8/3/2007 9:27:22 PM EDT

Originally Posted By DocGKR:
These new weapons would shoot 7 mm bullets of 120-140 gr at 2800-2900 f/s.


Those specs are closer to what we'd expect from a 7mm-08. I don't see how you are going to squeeze that kind of performance from a smaller cartridge case without having unacceptably high pressures.
Link Posted: 8/3/2007 9:34:54 PM EDT

Originally Posted By dewatters:

Originally Posted By DocGKR:
These new weapons would shoot 7 mm bullets of 120-140 gr at 2800-2900 f/s.


Those specs are closer to what we'd expect from a 7mm-08. I don't see how you are going to squeeze that kind of performance from a smaller cartridge case without having unacceptably high pressures.


Maybe, and this is just a guess, it's like the .260 and the 6.5X47.

Lotsa stuff you can do.
Link Posted: 8/3/2007 10:39:56 PM EDT
Hopefully we'll be shooting some new loads in 16-18" rifles in the next week or two rather than in test barrels, I'll see if we can post the results. Some of the 120 gr 7mm-08 loads we were testing were getting up into the low 3000's...
Link Posted: 8/4/2007 5:24:57 AM EDT
[Last Edit: 8/4/2007 5:26:13 AM EDT by mike_nds]
Link Posted: 8/4/2007 10:50:46 AM EDT
7PPC-long, several years old, PacNor SS Polygon 20" bbl
Uses either 6.5 Carcano brass or - courtesy of M9Powell - 6.5 MS brass which is a lot cheaper.

Can be loaded to 2.31" to fit the CP mags or else with the 139 load needs to be about 2.50"

Link Posted: 8/4/2007 10:53:26 AM EDT
[Last Edit: 8/4/2007 5:42:24 PM EDT by MartytW]
whoa, double tap, too much coffee
Link Posted: 8/4/2007 12:55:02 PM EDT
[Last Edit: 8/4/2007 12:56:39 PM EDT by M9Powell]
A 2.5" 7mm ctg is interesting as a hunting rd in an AR or as a DMR, but its too much for a true assault rifle role. M9

PS Might also be useful as a Squad auto in a HB varient or even beltfeed in a SAW.
Link Posted: 8/4/2007 1:09:35 PM EDT

Originally Posted By MattM_Gilbert:

Originally Posted By DocGKR:
The 6.5 mm Grendel is inhibited by this same limitation, with the added deficit of using the weak 7.62 x 39 mm AR15 bolt design that has a history of premature failure.


Doctor Roberts,

The statement quoted above is rather open ended, and I cannot discern whether the deficit you are referring to is one of reputation, solid mechanics, or QA for the end product.


I'd say he is just stating the obvious. Colt & CMT have both discontinued this boltface. It's been used for years & has always caused problems unless pressures are kept low. M9
Link Posted: 8/4/2007 1:23:55 PM EDT

Originally Posted By MattM_Gilbert:A solid mechanics deficit is readily surpassed in material selection. There are many newer alloys superior to Carpenter 158 for this bolt application; advantages realized most at temperatures above 750 F.
Matt M



Yes I'm quite sure you are correct. The problem is that AFAIK using those materials will drive the cost up substantially. Mostly due to the increased difficulty of machining the bolt. MGI has made such bolts & they say it'll cost around 200 bucks for a bolt. The barrel on an AR will be long gone before the bolt gets anywhere near that temp. The problem is not temp, it's metal fatigue & shear strength. As far as credentials go I don't think you need divulge any, unless you want to. If you're an idiot it'll soon be obivious. If you ain't, that'll soon be obvious also. M9
Link Posted: 8/4/2007 5:38:06 PM EDT
You might call it an intermediate ctg truly enough & you might pack it into an AR like weapon. But I think a lot of people don't realise just how littte a ctg it takes to be controllable in F/A in a 6 to 7 lb weapon. Such a ctg might be light recoiling in semi. But in F/A the rds will be in the air over the tgt. Thats not effective F/A. A 9 mm SMG weighing 8 to 9 lbs is much more controllable in F/A than an AR15 in 5.56. You might make it more controllable with a good muzzle break, but I have yet too see one that was both effective & quiet enough for a combat weapon. M9
Link Posted: 8/4/2007 6:01:56 PM EDT
I can hold 28 rounds in one burst on a playing card at 5 yards, shooting an M4A1.

For breaking contact or ambushes all you need is a lack of muzzle rise, it doesn't have to compare to the M4A1.
Link Posted: 8/4/2007 6:08:56 PM EDT

Originally Posted By M9Powell:
... But in F/A the rds will be in the air over the tgt....


That's a matter of training; or lack thereof.

We know the military is unlikely to consider this round, and many PD's don't have F/A outside of SWAT.

You're singular focus on issues that effect very few of the people who might BUY these types of weapons is tiresome. Truly.
Link Posted: 8/4/2007 6:16:58 PM EDT

Originally Posted By Combat_Jack:
I can hold 28 rounds in one burst on a playing card at 5 yards, shooting an M4A1.


I've never tried that....I might though. Interesting control method.
Link Posted: 8/4/2007 6:20:50 PM EDT
You have to get really, really low and lean aggressively forward. Stand up in a normal shooting stance and the group will loosen up, but who cares? FA is limited and not for point fire anyway.

But dayum it sure is fun!
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