How could or should the 6.5 mm Grendel be improved?

[stanc]

Would the improvements in performance over the Grendel really be worth the additional weight?

Increasing mag well size would add negligible weight, but enable use of thicker-walled, polymer or carbon steel mags. As far as the benefits of beefed up bolts, etc, I dunno.

I think our best bet here is to get a LMG built to accommodate the Grendel and see what kind of attention that attracts.

Concur. Sadly, I doubt that anybody here has the $$$$$ to finance such a project.

Then if we can get a steel core FMJ bullet developed, so we can prove our assumptions.

The mythical Wolf steel case ammo reportedly has a steel core FMJ. If it ever reaches these shores, that should provide a good basis.

However, some aspects of the military utility of 6.5 Grendel could be tested using currently available COTS rifles and ammo. It just requires sufficient interest on the part of Grendel proponents.

[cory]

Are you comparing weight to the 5.56 NATO or to the 7.62 NATO?

I was referring to woohoo's suggested redesign of the ar 15 platform, and the weight it would add.

[SHORT-N-SASSY]

Reviewing some of the interesting posts on this thread. I think I asked the wrong question.

Perhaps, I would have made life easier for myself if I had asked: what could be done to help military and LE users accept and use the 6.5 mm Grendel more widely?

The supplementary question is: is it good enough as is? If not, what could or should be done to improve it.

It has also been mentioned using high-power propellant to give the projectile increased velocity and energy.

And, just yesterday, from woohoo, ". . . Design and manufacture a stronger bolt and extension. A few stronger designs already exist. . . ."

Consider the muzzle velocities from a 16.5-inch bolt gun chambering a cartridge, which case is longer (1.92" vs 1.52"), case rim is wider (.473" vs .442), case capacity is greater (53 gr. H2O vs 35 gr.) and overall length is longer (2.82" vs 2.26"), than the 6.5mm Grendel: the 6.5mm Creedmoor --- Short Barrel 6.5mm Rifle - Sin City Precision 6.5mm Creedmoor http://www.sincityprecision.com/?p=1503.
2575 fps with the 139-grain Lapua Scenar, 2750 fps with the 123-grain Lapua Scenar, from a 6.5mm Creedmoor 16.5-inch bolt gun.

It's been reported in these pages that 2700 fps, with the 139-grain Lapua Scenar, was attained from a 6.5mm Grendel 22-inch bolt gun (CZ527) --- and, extrapolating, 2550 fps, in a 16 to 16.5-inch barrel.

All of which prompts me to conclude that an "enhanced" 6.5mm Grendel is the answer. And, all that is needed is an upgraded (read: "Big Bolt") AR-15/M16/M4 Bolt-Barrel Extension.

And, if we're ready to move to a Bullpup configuration --- allowing a still-longer barrel length, in a shorter overall length than is possible in existing AR-15-type platforms, as Tony Williams has stated --- there's an instant ambi left/right ejection design (presently incorporated in the ARX-160 and ARX100) that removes a significant downside to the Bullpup consideraton.

If only the Military Top Brass would start thinking outside the box!

[woohoo]

And, just yesterday, from woohoo, ". . . Design and manufacture a stronger bolt and extension. A few stronger designs already exist. . . ."

Consider the muzzle velocities from a 16.5-inch bolt gun chambering a cartridge, which case is longer (1.92" vs 1.52"), case rim is wider (.473" vs .442), case capacity is greater (53 gr. H2O vs 35 gr.) and overall length is longer (2.82" vs 2.26"), than the 6.5mm Grendel: the 6.5mm Creedmoor --- Short Barrel 6.5mm Rifle - Sin City Precision 6.5mm Creedmoor http://www.sincityprecision.com/?p=1503.
2575 fps with the 139-grain Lapua Scenar, 2750 fps with the 123-grain Lapua Scenar, from a 6.5mm Creedmoor 16.5-inch bolt gun.

It's been reported in these pages that 2700 fps, with the 139-grain Lapua Scenar, was attained from a 6.5mm Grendel 22-inch bolt gun (CZ527) --- and, extrapolating, 2550 fps, in a 16 to 16.5-inch barrel.

All of which prompts me to conclude that an "enhanced" 6.5mm Grendel is the answer. And, all that is needed is an upgraded (read: "Big Bolt") AR-15/M16/M4 Bolt-Barrel Extension.

And, if we're ready to move to a Bullpup configuration --- allowing a still-longer barrel length, in a shorter overall length than is possible in existing AR-15-type platforms, as Tony Williams has stated --- there's an instant ambi left/right ejection design (presently incorporated in the ARX-160 and ARX100) that removes a significant downside to the Bullpup consideraton.

If only the Military Top Brass would start thinking outside the box!

I've been messing with a case(capacity 42gr+-) that will push a 123 to around 2700fps from a 16"barrel(34gr 8208). More or less a Grendel stretched to 45mm. I'm not sure they would go for a full power round because of recoil and weight. Tony is thinking something that has a 20% weight reduction, less recoil but beats the 308 exterior ballistics.
It's wishful hoping but hey, that's how things get started.

[woohoo]

I was referring to woohoo's suggested redesign of the ar 15 platform, and the weight it would add.

Doubtful it will add even 2 oz. I have built a slim AR10 that is only 4 oz more than an AR15 and that action is over an inch longer.

[stanc]

http://www.defense-aerospace.com/article...-ammo.html

"Now Picatinny's EPR team is applying the [Enhanced Performance Round] technology to improve M80A1 7.62 mm ammunition that troops are scheduled to receive in 2014."

It looks like the standard for comparison of 6.5 Grendel will soon be 7.62 M80A1, not M80. Plan accordingly. :eek:

[Tony Williams]

http://www.defense-aerospace.com/article...-ammo.html

"Now Picatinny's EPR team is applying the [Enhanced Performance Round] technology to improve M80A1 7.62 mm ammunition that troops are scheduled to receive in 2014."

It looks like the standard for comparison of 6.5 Grendel will soon be 7.62 M80A1, not M80. Plan accordingly. :eek:

I doubt that this will make much difference since the new loading will almost certainly match the exterior ballistics of the M80, otherwise they'd have to change all of the MG sights. And it will weigh just as much, and recoil just as hard.

The only significant difference between M80 and M80A1 performance is likely to be in hard-target penetration (and possibly soft-target effectiveness), but that doesn't affect the ballistic comparisons since these don't take bullet construction into account.

It is bad news in one respect though - the more money the US Army pours into new loadings for 7.62mm and 5.56mm, the more resistant they're likely to be to a change in calibre.

[stanc]

I doubt that this will make much difference since the new loading will almost certainly match the exterior ballistics of the M80, otherwise they'd have to change all of the MG sights. And it will weigh just as much, and recoil just as hard.

The only significant difference between M80 and M80A1 performance is likely to be in hard-target penetration (and possibly soft-target effectiveness), but that doesn't affect the ballistic comparisons since these don't take bullet construction into account.

It is bad news in one respect though - the more money the US Army pours into new loadings for 7.62mm and 5.56mm, the more resistant they're likely to be to a change in calibre.

I'd say it's bad news in two respects: The resistance to change you noted, and improved terminal ballistics, which may or may not be matched even by a 6.5mm EPR. Otherwise, I agree with all of your comments.

[Bigfoot]

I'll share. Stretch the AR mags.

Before I decided on my triplets (lightweight bolt actions w same trigger pulls, LOP, scopes etc.) I was going to build a 6.5x43, a .15" longer Grendel. That would add 4 grains O2.

Simple really, mill the corners from the magwell and cut the rear section of the mags and replace them w l_l shaped section, squaring the backs and lenghtening the OAL by .15" IIRC. AR-10s, M1As and AKs dont need a big herkin bolt hold device, why does the AR? It would need a longer follower and I'm sure you could make it catch the bolt when empty but I'm a shooter/hunter so holding the bolt open isn't a priority like it would be for others.

If using the longer PRI mags you might decide to make the brass 44mm long. Working the brass is easy too. Take Prvi Partizan 7.62x39 blanks, cut em to length, neck em down and fireform. Would it be worth the trouble for 100 fps w the 123 SST? Don't know but combine that 10% additional capacity with a Superbolt and it might be worthwhile. I decided to stick w 5.56 and my -06 Lightweight BAR for my semi autos. But there's my idea, another option to consider.

[woohoo]

Would the improvements in performance over the Grendel really be worth the additional weight?

I think our best bet here is to get a LMG built to accommodate the Grendel and see what kind of attention that attracts.

Then if we can get a steel core FMJ bullet developed, so we can prove our assumptions.

Stan, answered you on some of this. It takes a class 10 ammo manufacturer to produce steel core bullets then it can only be sold to govt agencies. Only a #7 with a type 2 stamp can manufacture LMGs. They can be designed and tested but only sold to govt agencies after approval.

Just last week I received 2 new 25round Grendel mags. Knowing already about stacking/ swelling problems I checked them out by loading rounds in the mag. The tops of the cartridges do not touch the bottoms of the cartridges above. That causes the mags to swell but the mags create pressure on the cartridges in the mag. That needs to be addressed.
The increased bolt strength adds no weight to the system.
He asked "what could be done to help military and LE users accept and use the 6.5 mm Grendel more widely?"...Well that's just my opinion on how to improve the system.

[SHORT-N-SASSY]

The increased bolt strength adds no weight to the system.

Let's do it!

[stanc]

Let's do it!

Are you going to do it? Let us know how it works out.

[SHORT-N-SASSY]

Are you going to do it? Let us know how it works out.

"The knee bone's connected to the thigh bone, . . ." --- http://68forums.com/forums/showthread.ph...he-264-LBC, http://rifleshooter.com/2011/07/riflesho...del-60100/ (Scroll down page to 11th, 12th photos, click-on for close-up view).

[noone]

I've been messing with a case(capacity 42gr+-) that will push a 123 to around 2700fps from a 16"barrel(34gr 8208). More or less a Grendel stretched to 45mm. I'm not sure they would go for a full power round because of recoil and weight. Tony is thinking something that has a 20% weight reduction, less recoil but beats the 308 exterior ballistics.
It's wishful hoping but hey, that's how things get started.

A 6.5x45 Grendel is only 2mm short of the 6.5x47 Lapua. The 6.5x47 Lapua is pretty well established, and I'm not sure what the advantage of a 6.5x45 Grendel would be. I don't think it would fit into a AR15 sized magazine well as the bullet would have to be seated so far into the case that the case mouth would be over running the ogive. If you went to a Ar10 size rifle receiver, you might as well just go with the 6.5x47, or the 260 Remington...unless someone came up with a mid sized receiver that was between the AR15 and the AR10. If you could do that, and have the system with a "big bolt" concept, you would really be onto something.

[stanc]

A 6.5x45 Grendel is only 2mm short of the 6.5x47 Lapua. The 6.5x47 Lapua is pretty well established, and I'm not sure what the advantage of a 6.5x45 Grendel would be.

At least two advantages: Lighter weight, greater magazine capacity.

[woohoo]

A 6.5x45 Grendel is only 2mm short of the 6.5x47 Lapua. The 6.5x47 Lapua is pretty well established, and I'm not sure what the advantage of a 6.5x45 Grendel would be. I don't think it would fit into a AR15 sized magazine well as the bullet would have to be seated so far into the case that the case mouth would be over running the ogive. If you went to a Ar10 size rifle receiver, you might as well just go with the 6.5x47, or the 260 Remington...unless someone came up with a mid sized receiver that was between the AR15 and the AR10. If you could do that, and have the system with a "big bolt" concept, you would really be onto something.

We've been shooting the 6.5BRX in a AR15 since late 09. It is low capacity (10) using 15 round 6.8 mags but works fine for target and hunting. The 6.5x45 is something we are working on, it will have the same case capacity as the 6.5BRX. You are correct the 6.5x45(based on a Carcano) would be no advantage at all to civilian users. It would not work in a AR15 action or mag. The other mid sized thing was done back in late 09.

Add lower recoil than a 308 but better exterior ballistics to what Stan said.

[cory]

"The knee bone's connected to the thigh bone, . . ." --- http://68forums.com/forums/showthread.ph...he-264-LBC, http://rifleshooter.com/2011/07/riflesho...del-60100/ (Scroll down page to 11th, 12th photos, click-on for close-up view).

Where there any reports on the success of constructor's bolt? I'm sure he posted reports, but I'm not a member of that forum therefore I couldn't access his posts.

[woohoo]

Where there any reports on the success of constructor's bolt? I'm sure he posted reports, but I'm not a member of that forum therefore I couldn't access his posts.

We only made 50 PPC size bolts for 1 small batch of barrels. They are being used but we don't hear much unless something goes wrong. None have broken on the PPC size or BR size.
I still have the first 6BRX I made in 09. 36 gr of N550 will push a 95gr SMK to apx 3200fps.

[SHORT-N-SASSY]

We only made 50 PPC size bolts for 1 small batch of barrels. They are being used but we don't hear much unless something goes wrong. None have broken on the PPC size or BR size.
I still have the first 6BRX I made in 09. 36 gr of N550 will push a 95gr SMK to apx 3200fps.

Woohoo,

How would you compare the AR Performance 800 Series .30 Rem AR bolt & extension set, with Remington's Bolt-Barrel Extension design used in their R-15 .30 Remington AR rifle? Which of these two designs has the larger Bolt circle diameter and Barrel Extension diameter? And, other than diameter, does one design offer more than the other?

I'd like to see a side-by-side comparison test. My personal thought: these designs open up a whole new ball game for the AR-15 platform.

[woohoo]

I've only seen the Remington design 1 time at the SHOT show, I really have no idea what size they are. The only thing I can say about design is I tried to use large radii instead of corners to increase strength at the lugs.