Grendel as a Universal Infantry Cartridge

[LRRPF52]

When I look at automatic weapons with a constant recoil operating principle, they are plug-and-play designs that a soldier with no training can pick up, and put to use immediately with no other instruction than how to load and operate the mechanism. Since there is no real disruption of the sight picture with a constant recoil machinegun, you just walk the rounds into the target with immediate correction feedback. You don't even have to muscle the gun into a stable firing position, because it just tracks where you point it.

You can't fix cave-man, but you can make toys that cave-men can play with. If you give cave-men a Clingon Star Trek Scanner, it will be a paper weight or club.

[BluntForceTrauma]

Here's another chunk of anecdotal evidence speaking to long-range firepower needs in the hands of soldiers.

Link: http://kitup.military.com/2011/12/tank-snipers.html

Money quote: "More and more reports are coming out telling us that the Taliban in Afghanistan has finally figured out the limited range of American rifles and other small arms. Acting accordingly, we are told that they are maintaining as much stand off as possible when engaging US forces, remaining just outside the maximum effective range of our soldier’s ammunition while firing at them with heavy machine guns and RPGs. The Carl Gustaf has the potential to change that when employed properly. Existing systems…such as the M141 Bunker Defeat Munition, M72 LAW, M136 AT-4 and the SMAW, are only effective inside of 500 meters. The Army says the Carl-Gustaf [max effective range 1,000m] is more effective than waiting on mortars and less expensive than artillery or Javelin missiles.”

John

[JASmith]

John,

Thanks for pointing that out -- even I keep forgetting that we need to discuss combined arms as we go through this discussion.

Cheers!

[stanc]

Here's another chunk of anecdotal evidence speaking to long-range firepower needs in the hands of soldiers.

Link: http://kitup.military.com/2011/12/tank-snipers.html

Money quote: "The Army says the Carl-Gustaf [max effective range 1,000m] is more effective than waiting on mortars and less expensive than artillery or Javelin missiles.”

According to militarytimes.com, the M3 will be fielded to the 82nd Airborne. In the late 1990s and early 2000s, I participated in a forum composed mostly of veterans, from sergeants up to a general, and we tried to get the Army interested in the M3. (I even had an article in Infantry magazine that in part proposed this weapon be acquired for the 82nd.) That the leadership has finally seen the light is refreshing. Maybe there's hope for 6.5 Grendel...

Below: The high explosive, air burst round ought to be just the ticket for "discouraging" RPG gunners standing off at 900 meters.

Below: At 1:01 the HEAB fuze setting is shown.

[LRRPF52]

I was going to say that Ranger Regiment has been using the Carl Gustav for quite some time. Those are some impressive warheads.

The Taliban and their Mujahaideen origins are well aware of small arms ranges, and seem to favor far ambushes outside of 800m+, especially if Dshka's are available. You can use thermals with trail teams as you bound, regardless of time of day, to detect human signatures, and initiate on your terms, but most small unit leaders think too much in a very small box, and don't use the tools available to them. This problem is systemic and is found throughout the US modern war experience.

[stanc]

Finally came across a combat video with a carbine fired full-auto (@ 1:35, below).

Still haven't seen any speed loading, though. Mag changes in this vid are slow and deliberate, as in all previous.

Note the rifle-length rail and lack of BUIS.

http://www.youtube.com/watch?v=JwDxpST8EU8

[Variable]

Pretty cool vid Stan. It's pretty interesting. I'd like to have a can on (if I were the guy shooting through the portal) to reduce my dust signature and all of the debri that was kicking up---- BUT I'm a long way off of ever qualifying to walk in those guys shoes, so I have no idea if it would have been practical or not. I'm not at all qualified to even comment intelligently, and certainly not to critique or criticize, so I'll just ponder.

I do know I'm dang sure jealous of their 203s, that guy's Specter sight, and I wish I had their ammo too though.LOL!

[stanc]

A lot of military users are now starting to test the 6.5 mm Grendel. Fired from a 24" barrel, it provides impressive long-range performance, which is superior to that of 7.62 mm NATO. From a 16.5" barrel, it is less good than 7.62 mm NATO, but far exceeds 5.56 mm NATO.

Could a militarised 6.5 mm Grendel be an ideal choice? I don't know, but expect to hear a lot more about this round over the next 12 months or so.

http://forums.delphiforums.com/autogun/messages?msg=5699.59

[Trooper]

Look to have a general purpose (universal) cartridge it is going to have to be between 6.5 and 7mm. The 6.5mm works better due to less recoil.

The next aspect is getting the round to 2500 fps out of the barrel using a 140 grain bullet. That is the standard, set by the 6.5x55 Swedish Mauser. So far the .260 Rem, the 6.5 Creedmoor and and the 6.5x47 Laupa meet those requirements but with longer cases. As do wildcats like the 6.5 BRM which is based on the .30-30 case. The problem is that we can get a 140 gn. bullet to go 2500 but it takes a longer case than would fit into the current AR platform.

So could we make 6.5mm GPC that pushes a 140 gn. bullet 2500 fps? And make it smaller than a .308 (7.62x51)?

[LRRPF52]

The Grendel is capable of pushing a 140gr to 2500fps from a stronger action, but with a different COL. The problem is, you don't want a 140gr for riflemen. Too much recoil, too much weight.

130gr is the maximum you really need, and even then, I don't want riflemen hosing away in close quarters with that load. 130gr is perfect for a belt-fed, and can be pushed to 2600fps from a stronger action with 2.400". BjornF16 has done just that with his Savage and a 20" barrel.

[SHORT-N-SASSY]

Look to have a general purpose (universal) cartridge it is going to have to be between 6.5 and 7mm. The 6.5mm works better due to less recoil.

The next aspect is getting the round to 2500 fps out of the barrel using a 140 grain bullet. That is the standard, set by the 6.5x55 Swedish Mauser. So far the .260 Rem, the 6.5 Creedmoor and and the 6.5x47 Laupa meet those requirements but with longer cases. As do wildcats like the 6.5 BRM which is based on the .30-30 case. The problem is that we can get a 140 gn. bullet to go 2500 but it takes a longer case than would fit into the current AR platform.

So could we make 6.5mm GPC that pushes a 140 gn. bullet 2500 fps? And make it smaller than a .308 (7.62x51)?

It's been reported that 2650 - 2700 fps, with the 139-grain Lapua Scenar projectile, has been achieved, from a 22" bolt-action rifle chambered for the 6.5 Grendel. Was that 139-grain Scenar loaded to AR-15 magazine length, or extended? If extended, to what overall length?

It's been reported that "Big Bolts" can operate at/up to 60,000 psi, in the standard-length AR-15 action. Unencumbered by the limitations the laws of Bolt Thrust impose on the 6.5 Grendel, in the standard AR-15 Bolt-Barrel Extension, what velocities can be achieved in a "Big Bolt" AR-15?

ETA: LRRPF52 Reply was posted, while I was typing mine. I think it's fair to state that his suggestion represents the solution.

[cory]

Look to have a general purpose (universal) cartridge it is going to have to be between 6.5 and 7mm. The 6.5mm works better due to less recoil.

The next aspect is getting the round to 2500 fps out of the barrel using a 140 grain bullet. That is the standard, set by the 6.5x55 Swedish Mauser. So far the .260 Rem, the 6.5 Creedmoor and and the 6.5x47 Laupa meet those requirements but with longer cases. As do wildcats like the 6.5 BRM which is based on the .30-30 case. The problem is that we can get a 140 gn. bullet to go 2500 but it takes a longer case than would fit into the current AR platform.

So could we make 6.5mm GPC that pushes a 140 gn. bullet 2500 fps? And make it smaller than a .308 (7.62x51)?

Are you talking 2500 fps out of a 24" or a 20" barrel?

If we're talking a 24" barrel I believe that's possible with the Grendel and the current AR15 platform. I've pushed the SST 140gr to 2400 fps using CFE and have some loaded that I believe I'll get to 2450+ fps. It will likely be a hot load though. Note: I don't have a particularly fast barrel.

Now if we introduced a powder designed for the Grendel and a 140gr projectile, I believe we can do that safely, but the COL tolerances in the manufacturing process will have to be strict, as it'll need to be loaded to mag length.

Our current limitation is not the case but the platform. Let's be honest if the military switches to a GPC, it won't modify any of the current m4s. It'll simply buy new rifles and give the old ones to foreign countries who will eventually shoot at us with our own rifles.

The greatest advantage to using a cartridge that fits in the AR15 platform is it does NOT require retraining our military forces on a new platform. It allows them to keep using a platform they are very efficient with.

Let's take this opportunity and build the AR12. The Grendel needs more mag width as much as it needs more mag length. However, it only needs an additional .01"-.02" both ways. (those measurements are off the top of my head and may not be exact.) It also needs a beefed up barrel extension and bolt, preferably with rounded lugs.I'm assuming we'll need to push the Grendel to 58 ksi for military purposes.

With all those changes we'll still have significant weight savings over the AR10 and a platform that our military is efficient with.

Side note, I believe this platform would lead to a 7mm AR round, that'll be limited but very capable, much the same way the Grendel is in the AR15.

[cory]

The Grendel is capable of pushing a 140gr to 2500fps from a stronger action, but with a different COL. The problem is, you don't want a 140gr for riflemen. Too much recoil, too much weight.

130gr is the maximum you really need, and even then, I don't want riflemen hosing away in close quarters with that load. 130gr is perfect for a belt-fed, and can be pushed to 2600fps from a stronger action with 2.400". BjornF16 has done just that with his Savage and a 20" barrel.

Great point. +1

However, I don't know if I wouldn't want to see 140gr for a belt feed.

[woohoo]

The greatest advantage to using a cartridge that fits in the AR15 platform is it does NOT require retraining our military forces on a new platform. It allows them to keep using a platform they are very efficient with.

Let's take this opportunity and build the AR12.

123gr @2800fps out of a 20" barrel takes a cartridge with apx 42gr case capacity when loaded to pressure that would work in combat. 6.5x45 with an COAL of 2.6-2.7" based on the Carcano case. Keepin mind all bullets will be green from here on out...a 140 would be 1.5" long
"12" prototype

[JASmith]

I did an analysis last year using the GMX shape factor, and QuickLoad for velocity estimates. The parametric ran from about 75 grains up to the GMX weight (Sneaky R U listening?).

The bullet that seemed to have the best infantry-specific point blank range was between 95 and 105 grains. The PB was based on, I believe, the nominal 18" high torso.

And, yes, a bullet for the the machine gun is a question to ponder. One of the opportunities to think about is that the machine gun can indeed be designed to handle the bolt-thrust from higher intensity loadings that would fatigue the carbine bolt faster than comfortable. If the COAL is kept short enough to work in carbines, then the hotter MG round can be used in emergencies at ranges where the difference in trajectory is not an issue. In these emergency situations, a reduced bolt life is reasonable. First this kind of emergency won't happen very often, if at all, with modern logistics. Second, the bolts can be readily swapped out very soon after the emergency passes.