Grendel Evolution - AR10

[cory]

The AR47 thread started by calshipbuilder started a conversation on how to obtain the full potential of the Grendel. This conversation led into a potential AR10 Grendel.

I thought I'd moved that conversation in its own thread in hopes of bringing individuals to the conservation, who otherwise have missed the conversation. Particularly those whose industry experience would bring unmeasurable insight to the conversation. Bill, Mark cough... cough.

I'll see if I can't move most of the conversation into a following post.

Note: The intent of the AR10 Grendel is to demonstrate the benefit of an AR15/10 Hybrid.

[cory]

These are quotes inline form http://www.65grendel.com/forum/showt...270-AR-47-Gren

If something seems to be missing it probably is, refer to the original posts.

Okay. What platform do you suggest?

My initial suggestion is to go with a billet AR15/10 hybrid. And explore the limits of this cartridge.

I take that back. My initial suggestion would be to build a Grendel in an AR10 platform. I believe this would only take a redesigned bolt? Correct me if I'm wrong.

If we show we can approach 260 velocities with significantly less powder, I believe we can make a strong case for an AR10/15 hybrid.

When I say approach I mean if we can get at least in the middle of AR15 Grendel Velocities and 260 velocities I think we can make a strong case. My initial thought is I think we could get to the high side of that.

Remington did just that, with their Remington R-15 chambered for the .30 Remington AR: an AR-10-size Bolt-Barrel Extension, in an AR-15-size platform. But, they missed the boat, by going with the .30 RAR, instead of a full-pressure 6.5mm Grendel.

That wouldn't have helped the grendel any, its still an ar-15 magwell yhat holds it back from extra velocity, not the bolt.

If you go to a full size ar-10 sized lower and an ar-15 sized upper it would make more sense to go with a 260, or invent an all new round based on those dimensions rather than just increasimg the pressures with the grendel.

Obviously, a slightly longer Cartridge Overall Length (COL) for the 6.5mm Grendel would be desirable. But, you're missing the MAJOR culprit, here: Increased Bolt Thrust http://www.beyond556.com/bboard/show...olt-Thrust-FAQ. An AR-10-size Bolt-Barrel Extension, in an AR-15-size platform, would solve that problem. I dont' want to go to the longer, heavier AR-10 platform. That would defeat the purpose of the short-n-fat concept, which the 6.5mm Grendel so boldly represents. What we need is an "AR-15 on steroids."

A modified magazine would allow a slight increase in the COL.

Okay. What platform do you suggest?

My initial suggestion is to go with a billet AR15/10 hybrid. And explore the limits of this cartridge.

I take that back. My initial suggestion would be to build a Grendel in an AR10 platform. I believe this would only take a redesigned bolt? Correct me if I'm wrong.

If we show we can approach 260 velocities with significantly less powder, I believe we can make a strong case for an AR10/15 hybrid.

When I say approach I mean if we can get at least in the middle of AR15 Grendel Velocities and 260 velocities I think we can make a strong case. My initial thought is I think we could get to the high side of that.

Remington did just that, with their Remington R-15 chambered for the .30 Remington AR: an AR-10-size Bolt-Barrel Extension, in an AR-15-size platform. But, they missed the boat, by going with the .30 RAR, instead of a full-pressure 6.5mm Grendel.

That wouldn't have helped the grendel any, its still an ar-15 magwell yhat holds it back from extra velocity, not the bolt.

If you go to a full size ar-10 sized lower and an ar-15 sized upper it would make more sense to go with a 260, or invent an all new round based on those dimensions rather than just increasimg the pressures with the grendel.

Obviously, a slightly longer Cartridge Overall Length (COL) for the 6.5mm Grendel would be desirable. But, you're missing the MAJOR culprit, here: Increased Bolt Thrust http://www.beyond556.com/bboard/show...olt-Thrust-FAQ. An AR-10-size Bolt-Barrel Extension, in an AR-15-size platform, would solve that problem. I dont' want to go to the longer, heavier AR-10 platform. That would defeat the purpose of the short-n-fat concept, which the 6.5mm Grendel so boldly represents. What we need is an "AR-15 on steroids."

A modified magazine would allow a slight increase in the COL.

We're capable of operating at max safe pressure on the bolt with the current max COL. Without a beefed up bolt increasing case capacity is pointless.

Would an AR10 lower not increase our COL? I'm not familiar with the AR10 as I've never owned one. What's the max COL for the 308 in the AR10?

Have you ever looked at how much powder it takes for the 260 to reach the velocities it does? It takes ~45grs to push the 123gr projectile to 2900 fps. The Grendel is getting 2600 fps with ~31grs. Both using 24" barrels. The Grendel is an incredibly efficient round.

An "AR-15 on steroids," indeed: https://68forums.com/forums/showthre...or-the-264-LBC and http://rifleshooter.com/2011/07/rifl...r-model-60100/ (Scroll down the page a dozen photos to "R-15 bolt carrier group" and "R-15 bolt assembly." Click-on those images to get a close-up view of the difference between the AR-15 Bolt and the AR-10 Bolt, keeping in mind "Bolt Thrust FAQ.").

Isn't constructor on here by another handle?

Have you heard rather he has any plans on producing the beefed up bolt and extension again in the near future?

I guess you guys missed the JK at the end of my post I was just kidding around I offered some constructive ideas earlier in the thread about being limited in oal and case capacity an ar10 platform would allow an oal of 2.8 allowing a few extra grains of powder in addition to allowing practical the use of 140 grain projectiles and providing all the beefed up bolt you could ask for

in bolt guns i have seen data for Grendel pushing 140 grain to 2700fps in an ar10 it should be able to com pretty close to that which is 260 range

Extrapolating, I see 2500+ fps, from a 16 1/2-inch barreled 6.5mm Grendel bolt-action/Big Bolt-Barrel Extension AR-15, with the 139-grain Lapua Scenar projectile, approaching what the 6.5mm Creedmoor delivers with that projectile, from the same barrel length. http://www.sincityprecision.com/?p=1503

Herd is a article about a Grendel f-class build they got 2760 fps with jlk vld 130s granted it is a 28" barrel www.6mmbr.com/gunweek027.html I am sure the loads were well over sammi pressure

There was another article which I can not seem to find but it was comparing 6.5 and 6.8 ar15s along with a 24 inch Grendel bolt gun built on a cz527

Thanks, cory. I needed that.

In my [our] view, a firearm design is a work in progress, an idea that is constantly evolving. Consider the AR-15-based, downward-ejecting "raw Bullpup," in the accompanying photo, that's ready for the next planned stage: upgrading to a 6.5mm Grendel Barrel and Bolt.

It's all about "the challenge."

LaRue PredatAR 16" 7.62 reportedly weighs 7.75 lbs bare:

http://www.laruetactical.com/16”-larue-tactical-predatar-762

Currently chambered in 308 only, but it should be capable of handling numerous other cartridges.

[cory]

Has anyone here attempted to load a metal or Pmag AR10 mag with Grendel ammo? If so how many would fit comfortably and how did it seem to function?

[Ridgerider]

And the point is?

[woohoo]

I know I am probably not the right person to say this but. I'm not worried about bolts breaking since 2007 when I modified a LWRC 9310 bolt. I've run the Grendel so hard the cases swell to look like a belted magnum. Bill W. has also pushed the G very hard from the posts I read here. You may be able to get another 100fps over what Bill A posted as max loads many years ago. Because of the case length the bullets normally don't take up much of the powder space so even loaded longer than mag length I don't think you'll see more than another 50fps. The limiting factor is the max pressure usable in the Grendel case.
A bolt rifle with a chamber that is fully supported will stop the belted magnum look but the pressure is still there. Over 60 k you are taking a chance of rupturing the case.
I made a small batch of 50 -264/G barrels with big extensions and bolts a few years ago. The velocities were the same as we have always seen.
As for the mag question a 45mm long Carcano case feeds fine out of Pmags.

[XcountryRider]

I know I am probably not the right person to say this but. I'm not worried about bolts breaking since 2007 when I modified a LWRC 9310 bolt. I've run the Grendel so hard the cases swell to look like a belted magnum. Bill W. has also pushed the G very hard from the posts I read here. You may be able to get another 100fps over what Bill A posted as max loads many years ago. Because of the case length the bullets normally don't take up much of the powder space so even loaded longer than mag length I don't think you'll see more than another 50fps. The limiting factor is the max pressure usable in the Grendel case.
A bolt rifle with a chamber that is fully supported will stop the belted magnum look but the pressure is still there. Over 60 k you are taking a chance of rupturing the case.
I made a small batch of 50 -264/G barrels with big extensions and bolts a few years ago. The velocities were the same as we have always seen.
As for the mag question a 45mm long Carcano case feeds fine out of Pmags.

Right this would not be a Grendel it would be something else with a good mythological name. A good place to start is just the 30AR. Is that AR modification patented? Could someone take the concept and neck it down to a 6.5? Us 30AR brass or something close? You went with Creedmore brass for your 270AR design with probably a good reason instead of 30AR. Can you tell us why?

[WildBill3/75]

If you are building on an ar10 I'd go with the 6.5 creedmoor.

[woohoo]

Right this would not be a Grendel it would be something else with a good mythological name. A good place to start is just the 30AR. Is that AR modification patented? Could someone take the concept and neck it down to a 6.5? Us 30AR brass or something close? You went with Creedmore brass for your 270AR design with probably a good reason instead of 30AR. Can you tell us why?

With longer bullets like the 6.5s and 6mms you need a short case where the ogive of the long bullet can be loaded .040" in front of the case so the full dia bullet will span over the .015" long cone area in front of the case and lay in the freebore to align the bullet. I wanted to use the wide selection of 130gr bullets in the 270AR so I could use a longer case and get more capacity while doing it. The 270AR has 44.7gr H2O capacity which is .7 more than the 30RAR. The rim size is .473 so 243-308 brass can be used, Savage or what ever. A 6.5BRX has 42 gr H2O capacity, for the long 6 and 6.5mm bullets it is the correct length. If it was me catting a 6.5 (already have)I would use the Lapua BR brass not the hard to find 30RAR brass. The lapua quality is there, I would sacrifice the 2 gr just to stay clear of the Remington brass.
A BRX or any cat with a cap of 42gr will push a 123gr bullet to apx 2800fps out of a 20" barrel. I have a 6.5x45 cat based on the Carcano case for an AR12, it has the same cap as the BRX.

[Tedward]

I think you might be onto something. I think your thinking of using a 6.5/.264 projectile in a AR-10 case. If so, will it fit into a renecked .308? I don't know enought about the AR-10 but maybe a 6.5 Creedmore or 270 is the same thing. bigger case with a 6.5 projectile.

[cory]

I know I am probably not the right person to say this but. I'm not worried about bolts breaking since 2007 when I modified a LWRC 9310 bolt. I've run the Grendel so hard the cases swell to look like a belted magnum. Bill W. has also pushed the G very hard from the posts I read here. You may be able to get another 100fps over what Bill A posted as max loads many years ago. Because of the case length the bullets normally don't take up much of the powder space so even loaded longer than mag length I don't think you'll see more than another 50fps. The limiting factor is the max pressure usable in the Grendel case.
A bolt rifle with a chamber that is fully supported will stop the belted magnum look but the pressure is still there. Over 60 k you are taking a chance of rupturing the case.
I made a small batch of 50 -264/G barrels with big extensions and bolts a few years ago. The velocities were the same as we have always seen.
As for the mag question a 45mm long Carcano case feeds fine out of Pmags.

After short and sassy's post I was hoping you'd get in on this conversation.

I figure the gains on the 100gr class would be negligible if any. If we can gain a solid 100 fps with the 123gr class of projectiles, while staying within 60ksi, we're approaching 260 velocities. That would be a nice gain.

I think we'd see the real benefits in the 140gr class of projectiles. A 24" bolt action should be able to get over 2600 fps while staying below 60ksi. If we can that velocity in an AR10 I think that would be worth the build.

Again the intent of this is to show the benefits to an AR15/10 hybrid. An AR platform lighter than the AR10 that would allow a wider, longer magazine would benefit all of us, no matter what your choice of projectiles are.

[XcountryRider]

After short and sassy's post I was hoping you'd get in on this conversation.

I figure the gains on the 100gr class would be negligible if any. If we can gain a solid 100 fps with the 123gr class of projectiles, while staying within 60ksi, we're approaching 260 velocities. That would be a nice gain.

I think we'd see the real benefits in the 140gr class of projectiles. A 24" bolt action should be able to get over 2600 fps while staying below 60ksi. If we can that velocity in an AR10 I think that would be worth the build.

Again the intent of this is to show the benefits to an AR15/10 hybrid. An AR platform lighter than the AR10 that would allow a wider, longer magazine would benefit all of us, no matter what your choice of projectiles are.

Right if it was an AR10 we already have the creedmore and 260 Remington. What would be cool is a 30AR R-15 platform shooting a 6.5. The weight of a AR-15 but near velocity of a Creedmoore.

[cory]

Right if it was an AR10 we already have the creedmore and 260 Remington. What would be cool is a 30AR R-15 platform shooting a 6.5. The weight of a AR-15 but near velocity of a Creedmoore.

Essentially that's what it is, but no one is going to invest in building that unless they see a benefit and a market for it. Why are going to design another wildcat when we haven't maxed out the potential of the Grendel. Doing that would give the best insight as to what the next best evolution needs to be.

[XcountryRider]

Essentially that's what it is, but no one is going to invest in building that unless they see a benefit and a market for it. Why are going to design another wildcat when we haven't maxed out the potential of the Grendel. Doing that would give the best insight as to what the next best evolution needs to be.

The 30AR lower isn't modified is it? I think that part is a standard AR-15 lower. You know a good shop for something like this is obviously woohoo's but I think his heart is in the 6.8 caliber. If i'm wrong i'm sure he'll correct me but what about Quality Arms they have already did a lot of work with modifying uppers http://www.qualityarms.net/. If the 30AR brass could be used then a close copy of the Remington AR30 bolt could be used saving a bunch of design work.

[woohoo]

After short and sassy's post I was hoping you'd get in on this conversation.

I figure the gains on the 100gr class would be negligible if any. If we can gain a solid 100 fps with the 123gr class of projectiles, while staying within 60ksi, we're approaching 260 velocities. That would be a nice gain.

I think we'd see the real benefits in the 140gr class of projectiles. A 24" bolt action should be able to get over 2600 fps while staying below 60ksi. If we can that velocity in an AR10 I think that would be worth the build.

Again the intent of this is to show the benefits to an AR15/10 hybrid. An AR platform lighter than the AR10 that would allow a wider, longer magazine would benefit all of us, no matter what your choice of projectiles are.

We made 50 -"12"s (No AR since "AR" stands for Armalite rifle...or so they say) in late 09 but were so busy with other things I couldn't get back to it until 6 months ago. I designed it to be a very light 308 but the 45mm Carcano case seems to be a perfect fit. I'm sure over the next few years there will be all kinds of new AR based rifle systems pop up. Like the Colt, think of the possibilities.

[woohoo]

The 30AR lower isn't modified is it? I think that part is a standard AR-15 lower. You know a good shop for something like this is obviously woohoo's but I think his heart is in the 6.8 caliber. If i'm wrong i'm sure he'll correct me but what about Quality Arms they have already did a lot of work with modifying uppers http://www.qualityarms.net/. If the 30AR brass could be used then a close copy of the Remington AR30 bolt could be used saving a bunch of design work.

The company that drills my deep holes have machines running 3 shifts around the clock drilling 5.56 and 6.8 barrels. He will not stop to retool to drill 6.5 or 308 barrels. I have been waiting over a year for a pile of 6.5 and 308 blanks but gave up 2 weeks ago. I've been waiting for a company to produce 7.62x39 extractors by contract for about 6 months. It's just tough getting some parts to build the 264/G. I made a batch of 6.5BRX barrels and have some 6BRX now. They sell slow so they aren't money makers, in this business it's about quick turnovers. I have to sell what sells quick.
Personally I shoot long range, always have. Cats are a hobby...a money wasting hobby.