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+--- Thread: 6mm Grendel Group Design Project (/showthread.php?tid=14502)
6mm Grendel Group Design Project - SDet - 11-25-2017
StoneHendge Wrote:Well there could be a lucky soul out there if they haven't spent all of their Black Friday money yet. Looks like McGowen actually has a 24" 6mm Grrrr in stock and ready to ship
http://mcgowenbarrel.com/shop/ar15-6mm-grendel-hbar-750-rifle-length-24-polished-ss/
Just let me know how it shoots while I wait for mine. And if you're a lurker, create an account lol
Edit: wtf? Clicked link after posting to confirm it worked - looks like it has 1/2" muzzle threads?
That's fine, I'd be chopping it to 18" anyway. But it is tempting.
6mm Grendel Group Design Project - LRRPF52 - 11-27-2017
CavityBackBullets Wrote:Lets just agree to disagree since I shoot them all. Do you?________________________________________________________________________________________
You have an extensive working experience with 6mm wildcats between the 2 cases?
This one is pretty basic math.
We want to be able to shoot ogive lengths that can't be loaded into a 6.8 case without cutting down the case length significantly.
Grendel case is a neck-size operation and done without losing capacity.
Measure the magazine well limitations, then the bullets we want to be able to shoot.
Basic addition. The room isn't there for a 6.8 wildcat case to shoot 105s and 107s unless you cut the case down so far, reducing case capacity and velocity as a result.
6 PDK, 6mm Hagar, 6 DTI, 6x6.8, 6mm SPC, etc all don't have the ability to load 105s and 107s to mag length.
I just measured a 105gr Nosler RDF in a 6.8 case without moving the shoulder.
2.440" COL. AR15 magazine well is 2.395".
105gr Nosler RDF already drops into 6mm AR and 6mm AR Turbo.
This shouldn't be too hard to figure out.
6mm Grendel Group Design Project - CavityBackBullets - 12-04-2017
LRRPF52 Wrote:________________________________________________________________________________________
You have an extensive working experience with 6mm wildcats between the 2 cases?
This one is pretty basic math.
We want to be able to shoot ogive lengths that can't be loaded into a 6.8 case without cutting down the case length significantly.
Grendel case is a neck-size operation and done without losing capacity.
Measure the magazine well limitations, then the bullets we want to be able to shoot.
Basic addition. The room isn't there for a 6.8 wildcat case to shoot 105s and 107s unless you cut the case down so far, reducing case capacity and velocity as a result.
6 PDK, 6mm Hagar, 6 DTI, 6x6.8, 6mm SPC, etc all don't have the ability to load 105s and 107s to mag length.
I just measured a 105gr Nosler RDF in a 6.8 case without moving the shoulder.
2.440" COL. AR15 magazine well is 2.395".
105gr Nosler RDF already drops into 6mm AR and 6mm AR Turbo.
This shouldn't be too hard to figure out.
Actually it can shoot 105's with enough case capacity.
How its accomplished though I cannot reveal.
6mm Grendel Group Design Project - JASmith - 12-04-2017
CavityBackBullets Wrote:Actually it can shoot 105's with enough case capacity.Claims like this stretch credibilty.
How its accomplished though I cannot reveal.
At some point one will need to disclose any secret sauce and demonstrate the perfomance claims are valid within acceltable pressure limits.
6mm Grendel Group Design Project - bj139 - 12-04-2017
StoneHendge Wrote:Well there could be a lucky soul out there if they haven't spent all of their Black Friday money yet. Looks like McGowen actually has a 24" 6mm Grrrr in stock and ready to ship
http://mcgowenbarrel.com/shop/ar15-6mm-grendel-hbar-750-rifle-length-24-polished-ss/
Just let me know how it shoots while I wait for mine. And if you're a lurker, create an account lol
Edit: wtf? Clicked link after posting to confirm it worked - looks like it has 1/2" muzzle threads?
There is a bigger selection of .223 muzzle devices with 1/2"-28 threads.
Clearances would have to be checked between bullet diameter and ID of muzzle device.
I know you know this but I am only posting this in case there are others that try it. Maybe you have more ideas.
6mm Grendel Group Design Project - StoneHendge - 12-04-2017
bj139 Wrote:There is a bigger selection of .223 muzzle devices with 1/2"-28 threads.
Clearances would have to be checked between bullet diameter and ID of muzzle device.
I know you know this but I am only posting this in case there are others that try it. Maybe you have more ideas.
My guess is that whoever made the barrel screwed up. Seems like an odd caliber and configuration for a custom manufacturer to make for stock. Im sure theyd cut and rethread it for someone who asks. I did have a good visualization of Bugs Bunny handing a rifle with a muzzle device thats too narrow to Yosemite Sam.
6mm Grendel Group Design Project - bj139 - 12-04-2017
A2 flash hider would work just fine. Just look at the muzzle of your 5.56.
There is plenty of clearance. 0.01" additional each side of center.
6mm Grendel Group Design Project - Bwild97 - 12-04-2017
Why the .243" and not a .257" ?
In the quest for MV and BC, what are we loosing in hunting capability? Are sectional densities equal in 6mm and 6.5mm?
I thought the 6.5 Grendel already provided the optimal balance between target shooting and hunting performance.
6mm Grendel Group Design Project - bj139 - 12-04-2017
Bwild97 Wrote:Why the .243" and not a .257" ?
In the quest for MV and BC, what are we loosing in hunting capability? Are sectional densities equal in 6mm and 6.5mm?
I thought the 6.5 Grendel already provided the optimal balance between target shooting and hunting performance.
That was my original question as well.
The 6.5mm (.264") is midway between the beloved 30 cals for us old timers and the newbies 5.56mm.
It is just the ideal compromise.
Target shooters are looking for the last tiny advantage so the 6mm has value to them.
6mm Grendel Group Design Project - StoneHendge - 12-04-2017
bj139 Wrote:Just look at the muzzle of your 5.56.
Lol - my "new" 20" target 556 (ie, life after 22 Nosler) has a VG6 Epsilon on it - has about as much muzzle movement and recoil as a 22lr.
But for target, 6mm offers more than a "last tiny advantage." I'm pretty confident that my 26" 6mm Grrr barrel arriving today (yay!) will have ballistics nipping at the heels of what I do with 130's in my 6.5 S'more. To put it in perspective, I was having a lot of fun with a buddy yesterday shooting 1k in winds that ranged from the high teens to the high 20s. Drop and 20 mph wind drift were 24' and 8.5' with me S'more while drop and 20 mph wind drift were 29' and 11' in my 22" 6.5 Grendel shooting 123 gr Scenars. The S'more got more first shot hits, while follow up shots were faster with the Grendel due to lower recoil. That didn't equate into more second shot hits with the Grendel since it is more susceptible to wind speed fluctuation. But with 6mm Grrr, you would have the S'more 1st shot hit percentage combined with even lower recoil than 6.5 Grrr. At one point when I was on the Grendel, the wind got into the high 20s and my horizontal hold was 5 mils on a 16" (half mil) target - over 15' of wind drift. Was kind of crazy to dial the scope back to zero at the end of the day and take a look at what the crosshairs were actually pointing at with a 9.1 mil vertical and 5 mil horizontal hold
Bwild, I don't know if anyone even makes a .257 match target bullet. My interest in 6mm Grrrr is solely on the basis of target shooting, with the caveat that I consider p-dogs to be exploding targets.
6mm Grendel Group Design Project - bj139 - 12-04-2017
I think most of us here only have a pipe dream of shooting at 1000 yds. As in precision match grade pipe.
My home range only has 100 yds maximum, so I am resigned to the pursuit of sub MOA groups.
Isn't the last tiny bit your difference of 1 foot in hold left between 6mm and 6.5mm?
Just like the last tiny bit of shooting a 0.4 MOA group vs. a 0.6 MOA group.
6mm Grendel Group Design Project - LRRPF52 - 12-04-2017
Bwild97 Wrote:Why the .243" and not a .257" ?Good to see you again!
In the quest for MV and BC, what are we loosing in hunting capability? Are sectional densities equal in 6mm and 6.5mm?
I thought the 6.5 Grendel already provided the optimal balance between target shooting and hunting performance.
If we're limited to the AR15 magazine well dimensions, then .257" is really close to 6.5mm, suffers from a lot of the same challenges, but I'm a big fan of the .257 bore.
It has been neglected when it comes to bullet selection, but I really think is a great balancing point if we could get bullet manufacturers to support it.
I think this will actually happen moving forward, as Hornady has already done some work on the .257 Creedmoor. .257 Creedmoor was featured in a recent Handloader Magazine as well.
For competitive shooters in long range matches, most people want a .550 to .6 or higher G1, .275 to .3 + G7 bullet. That's easier to do in .257 and keep the recoil down than it is in 6.5mm (140gr + cup and core).
In a 6mm, that usually puts you in the 105gr + weight category.
It could be done in .257 with a 123gr - 130gr, but would be quite long for the AR15.
6mm Grendel Group Design Project - JASmith - 12-05-2017
Bwild97 Wrote:Why the .243" and not a .257" ?Best way to answer is to look at the .243 Win. It has a fine reputation but folks dont normally hunt elk and larger with it.
In the quest for MV and BC, what are we loosing in hunting capability? Are sectional densities equal in 6mm and 6.5mm?
I thought the 6.5 Grendel already provided the optimal balance between target shooting and hunting performance.
The 25-06 is occasionally used for elk because we can get 110 ton120 gr hunting bullets for it.
Trying to bridge the gap between 6 and 6.5 mm, however, feels more like an exercise for the sake completeness rather than wgenerating a new capability.
This is especially true now that one can get 110-115 gr 6 mm and be able to accurately shoot them with proper twist barrels.
6mm Grendel Group Design Project - bj139 - 12-05-2017
People complain about lighter bullets having less ringability on steel targets.
Doesn't the 6mm give up ringability for the sake of better ballistics?
6mm Grendel Group Design Project - BluntForceTrauma - 12-05-2017
bj139 Wrote:The 6.5mm (.264") is midway between the beloved 30 cals for us old timers and the newbies 5.56mm. It is just the ideal compromise. Target shooters are looking for the last tiny advantage so the 6mm has value to them.
This.
14 years ago, I would have been fine if they had first presented us with a .25 or .27 Grendel, but, heck, then again why not .26? .26 cal exactly splits the difference between .22 and .30. The intermediate of intermediate cartridges! Supreme efficiency balancing bullet mass, ballistics, and recoil.
I consider the 6.5 Grendel the best assault rifle cartridge possible within the confines of the AR platform, given high-capacity, double-stack magazines with a max 2.300 COL. This is why I love it.
It is also the best multi-role hunting cartridge in that platform.
It is also very good for informal target shooting, but technically and competitively speaking, is edged out in both drop and drift by a 6mm in the same case. (Or, as I've proposed above, a case stretched from 38.6mm to 40.4mm.)
So the 6.5 Grendel is a fantastic AR hunting round that can also be used for target shooting.
My proposed 6mmAR Turbo Stretched is a fantastic AR target round that can also be used for hunting.
Now, if we could get some of the newer hybrid, optimized ogives on long-range friendly 6.5mm 115-123 grain HPBTs, I think we could give 6mms a run for their money. Every time the major bullet makers come out with a "new" 6.5mm bullet with the same old fat, lazy tangent ogive (hello, Hornady 123gr ELD-M), I'm like, "Nooooo!!! Just put the Berger 140 Hybrid nose or Sierra 150 SMK nose on a 6.5mm 115gr and let us have a bit more velocity from the smaller Grendel case with a super sleek ogive. Why can't they just do it right the first time? It's so simple."
6mm Grendel Group Design Project - CavityBackBullets - 12-13-2017
JASmith Wrote:Claims like this stretch credibilty.
At some point one will need to disclose any “secret sauce” and demonstrate the perfomance claims are valid within acceltable pressure limits.
No disclosure when its someone elses case design and they shared the information with me.
What kills me with all this is why?
I mean Predatordown is as far as I know the Grendel long range king and he shoots mild loads out of his I believe 24in barrel at like 2450 fps.
6mm Grendel Group Design Project - stanc - 01-22-2018
BluntForceTrauma Wrote:Gentlemen, Warriors, and Vile Masses of The Horde: Lets put our heads together and spec out the ultimate 6mm cartridge based on the Grendel case. Release of the new .224 Valkyrie got me thinking about Grendel-based wildcats. I think 6mm is begging to be a factory round.Challenge accepted!
I already have in mind my perfect 6mm round. I challenge you guys to do better.
BluntForceTrauma Wrote:OK, heres my thinking. . . .I don't trust 30 degrees. When the US Army developed what became 7.62 NATO, they began with a 30-degree shoulder, then soon reduced it to 20 degrees for reliable feeding.
Start with a Grendel case, which has a case length of 1.520" or 38.6mm.
Next, take the bullet with the longest nose length that you intend to use: the gorgeous Berger 6mm 105 Hybrid with a nose length of 0.701.
Even though some magazines allow a COL of 2.300, lets hedge a bit for the sake of reliable feeding and declare our max COL to be 2.290. (Factory loads with shorter bullets could be loaded to standard AR COL of 2.260.)
Now, COL of 2.290 minus bullet nose length of 0.701 equals a max case length of 1.589. Lets just round it to 1.590" or 40.4mm.
THUS, WE NEED A BRASS MANUFACTURER TO INCREASE LENGTH OF GRENDEL CASES FROM 38.6MM TO 40.4MM!
Neck length of this brass will be on the short side for more case capacity, but should match the proven 6mm BRX of .210.
Shoulder remains at 30 degrees, for feeding reliability. I just dont trust 40 degrees for feeding from the magazine in an AR; I could be wrong, but thats my opinion as of today without further proof.
No military rifle cartridges have a 30-degree shoulder. The steepest are 7.5x55 Swiss at 28 degrees, followed by 6.5x55 Swede at 25 degrees. All others are 23 degrees or less.
BluntForceTrauma Wrote:Why not the 6.8 case cut down and necked down? Not as fat as a Grendel case, thus lacks capacity, thus lacks velocity.High velocity is not necessary, according to the original (modest MV/high BC) design philosophy of 6.5 Grendel and the 6mm SAW (below).
![[Image: 6mm-SAW-general-purpose-combat-cartridge.jpg]](http://abesguncave.com/wp-content/uploads/2016/03/6mm-SAW-general-purpose-combat-cartridge.jpg)
BluntForceTrauma Wrote:Thoughts from The Horde?I would opt to use the Valkyrie case, necked up to 6mm, and shoulder angle reduced to 23 degrees. Fits in existing M68 links, for machine gun use.
![[Image: larue_big3_06-720x497.jpg]](http://www.gunsandtech.com/wp-content/uploads/2017/10/larue_big3_06-720x497.jpg)
6mm Grendel Group Design Project - stanc - 01-22-2018
BluntForceTrauma Wrote:I consider the 6.5 Grendel the best assault rifle cartridge possible within the confines of the AR platform, given high-capacity, double-stack magazines with a max 2.300 COL.Taking into account military requirements, IMO the best assault rifle cartridge possible is the 5.45x39.
![[Image: dummy_7n6_01_01.jpg]](http://www.coolfx.us/images/dummy_7n6_01_01.jpg)
6mm Grendel Group Design Project - BluntForceTrauma - 01-23-2018
I consider the lack of 30 degrees to be simply hidebound, in-the-box thinking. But not the biggest deal. I strongly prefer 30, but could go either way. You gain a touch of case capacity and the supposed accuracy and throat-wear benefits, but nothing to write home about.
I could support a 6mm Valkyrie. And the 5.45x39 is a hell of a cartridge. One could do worse. . . . Both cartridges exhibit my approved "short case long bullet" principles. :p
A fully developed 6.5 Grendel (read developed and dedicated cartridges and loads) could have almost identical external ballistics and have a bit more mass for environmental barriers.
6mm Grendel Group Design Project - stanc - 01-23-2018
BluntForceTrauma Wrote:I consider the lack of 30 degrees to be simply hidebound, in-the-box thinking.That could perhaps be true of some of the world's armies. Or perhaps military cartridge designers generally chose to err on the side of cautious conservatism in order to ensure reliable feeding.
In the case of 7.62 NATO developers, the evidence shows they were not hidebound in their thinking on this matter. When development started in 1945, instead of rigidly copying the 17-degree shoulder of the venerable .30-06 case, they elected to use a 30-degree shoulder. It was only after a few years of test and evaluation that shoulder angle was changed to 20 degrees, a fact which says to me that the 30-degree shoulder likely caused feeding or chambering issues.
![[Image: IMG_0125L.jpg]](http://www.thefirearmblog.com/blog/wp-content/uploads/2016/03/IMG_0125L.jpg)