6.5 Grendel Magnum, version 2

I'm looking for a long range target AR15 and love the concept of the 6.5 Grendel. But Mike Milli over at DTech offers a wildcat 6.5 WSSM that has some advantages and some disadvantages to the 6.5 Grendel.

The 6.5 WSSM offers more velocity, always a good thing. The downside is that the case is longer than the Grendel case. The longer case means that the high ballistic coefficient bullets available in the heavier weights can not be seated properly and still function through the action of the AR15. Sure, you could single feed the rifle, but that sort of eliminates the whole point of using an AR15 as the basis for the build.

So here is my idea. Take a WSSM case, push the shoulder back so it is in the same position as the 6.5 Grendel shoulder. Stretch the neck size to 6.5mm and then trim it back to the same cartridge length overall as the 6.5 Grendel.

What do you think?

My thoughts are that it would be able to utilize the longest highest ballistic coefficient bullets available in 6.5, it would still function through an AR15 action, and it would probably deliver a heavy 140 grain target bullet at 200 to 300 fps faster to the target than the current 6.5 Grendel.

Practical? Worthwhile? Pointless?

Any ideas for improvement? Again, this is a round to push the AR15's 6.5 Grendel concept to its fullest potential, not as a military round, but as a long range AR15 target round that would deliver extreme accuracy at extreme range.

If you want more velocity in the AR platform, I think you'd want to know how reliable Oly Arms system is with their bigger bolt and bolt-face sized to handle the WSSM head size.

For velocity gains, I'd probably recommend going up to the AR10 platform and using one of the many bigger 6.5s: 6.5x47 Lapua, 6.5 Creedmore, .260 Remington.

John

If you want more velocity in the AR platform, I think you'd want to know how reliable Oly Arms system is with their bigger bolt and bolt-face sized to handle the WSSM head size. Well what I want is the best AR15 I can build for long range. That is why I was thinking of using the WSSM case to get a little more performance than the 6.5 Grendel. The WSSM case just has more capacity, even if you pushed the shoulder back so you could fit long 6.5mm VLD bullets into the magazine, you'd still have greater velocity with better bullets than the 6.5 Grendel can push. And bear in mind I'm not knocking the 6.5 Grendel, I think it is an awesome round, I just wonder if there can be an improvement.

For velocity gains, I'd probably recommend going up to the AR10 platform and using one of the many bigger 6.5s: 6.5x47 Lapua, 6.5 Creedmore, .260 Remington.

JohnAh but John, that totally defeats the exercise of trying to make the best AR15 for long range shooting! What I want to do is maximize the AR15.

It is possible that the 243 WSSM may be the best long range chambering for the AR15 with a Berger VLD 6mm bullet but I'm not sure the Berger 105gr VLD 6mm will fit into the AR15 magazine.

I'm looking for a long range target AR15 and love the concept of the 6.5 Grendel. But Mike Milli over at DTech offers a wildcat 6.5 WSSM that has some advantages and some disadvantages to the 6.5 Grendel.

The 6.5 WSSM offers more velocity, always a good thing. The downside is that the case is longer than the Grendel case. The longer case means that the high ballistic coefficient bullets available in the heavier weights can not be seated properly and still function through the action of the AR15. Sure, you could single feed the rifle, but that sort of eliminates the whole point of using an AR15 as the basis for the build.

So here is my idea. Take a WSSM case, push the shoulder back so it is in the same position as the 6.5 Grendel shoulder. Stretch the neck size to 6.5mm and then trim it back to the same cartridge length overall as the 6.5 Grendel.

What do you think?

My thoughts are that it would be able to utilize the longest highest ballistic coefficient bullets available in 6.5, it would still function through an AR15 action, and it would probably deliver a heavy 140 grain target bullet at 200 to 300 fps faster to the target than the current 6.5 Grendel.

Practical? Worthwhile? Pointless?

Any ideas for improvement? Again, this is a round to push the AR15's 6.5 Grendel concept to its fullest potential, not as a military round, but as a long range AR15 target round that would deliver extreme accuracy at extreme range.



what about starting with the .450 Bushmaster, a shortened .284?

Either should work, if you can make them feed reliably.

what about starting with the .450 Bushmaster, a shortened .284?
I believe the case for the WSSM is about the fattest case you can fit into the AR15 platform, anything with a smaller diameter would have a lower powder capacity. I do not have the case sizes for the 450 Bushmaster, but I believe the diameter to be well under the .555" base diameter of the WSSM. Not sure about the .284 Win, I know it has a rebated rim to bring the head size down to 308 size, but I don't know the case size.

I believe the case for the WSSM is about the fattest case you can fit into the AR15 platform, anything with a smaller diameter would have a lower powder capacity. I do not have the case sizes for the 450 Bushmaster, but I believe the diameter to be well under the .555" base diameter of the WSSM. Not sure about the .284 Win, I know it has a rebated rim to bring the head size down to 308 size, but I don't know the case size.


.500" LR

I am fairly new to the AR platform. I know that the AR-10 has a larger chamber area as it was designed for the .308 and the AR-15 was designed for the .223. What is the real mechanical difference between the two? Can a AR-10 upper be attached to and AR-15 lower, or are they two totally different systems?

I ask because I would like to get a .260 Remington type cartridge for the AR platform but don't know if I have to buy another lower to do it.

I am fairly new to the AR platform. I know that the AR-10 has a larger chamber area as it was designed for the .308 and the AR-15 was designed for the .223. What is the real mechanical difference between the two? Can a AR-10 upper be attached to and AR-15 lower, or are they two totally different systems?

I ask because I would like to get a .260 Remington type cartridge for the AR platform but don't know if I have to buy another lower to do it.
You cannot combine the AR10 with the AR15 or visa versa. Two totally different sizes. The AR10 being larger and the parts simply will not swap.

Yes, you can get a 260 Rem chambered for an AR10, but if you are serious about long range shooting you skip right past the 260 Rem and go right to the 6.5-284 round. Its a former wildcat target round that has been legitimized and is considered one of the best long range rounds for target shooting ever developed. It is basically the same length as a 308 but with a fatter case body and a rim that is the same size as a traditional 308.

If you want to stay with the AR15 platform and want 260 Rem performance, the closest you can get will be a Winchester Super Short Magnum round. Consider either the 243 WSSM or the 25 WSSM uppers for both are available from DTech, Accuracy Systems or Olympic Arms.

, but if you are serious about long range shooting you skip right past the 260 Rem and go right to the 6.5-284 round. Its a former wildcat target round that has been legitimized and is considered one of the best long range rounds for target shooting ever developed. It is basically the same length as a 308 but with a fatter case body and a rim that is the same size as a traditional 308.

If you want to stay with the AR15 platform and want 260 Rem performance, the closest you can get will be a Winchester Super Short Magnum round. Consider either the 243 WSSM or the 25 WSSM uppers for both are available from DTech, Accuracy Systems or Olympic Arms.

The two cases are more dissimilar than like; the 6.5-284 has much less body taper and a rebated rim to boot, which when combined with the longer straighter case, it sure isn't known for feeding via autoloaders very well.


The 6.5-284 has the advantage of sending the heaviest bullets above 3050 fps, to do this you need to seat the bullet out far, use a long tube and use lot's of slow burning powder. For long range target shooting most will shoot the heavy 140-142 grains bullets at around 2950-3050 fps, that's the magic window.

Concerning LR target shooting, nobody seats bullets at the OAL's that you typically see in reloading manuals. I would be concerned about the OAL of the 6.5-284 in an AR10 platform. For example, my 6.5-284 was setup so that on a fresh throat a 140 grain JLK VLD seated just off the rifling was around 3.090" long and IIRC the 140 SMK is just over 3.150" and these OAL's are are fairly typical for a target long range 6.5-284 setup.


For an AR10, either the 6.5x47, 6.5XC, 65 Creedmore or 260 Rem would all work.

I toyed with the 6.5 Win Short Stupid Marketing wildcat cartridge 5 yrs ago and I would never consider using it in an AR15, especially now since AR10's are more commonplace.

Mike

Thanks guys for setting me straight. I didn't think they would work together, but figured it wouldn't hurt to ask. I am a while away from getting a new upper anyway, as I just got a .223 and the wife will need to chew on that one for a little while.

I toyed with the 6.5 Win Short Stupid Marketing wildcat cartridge 5 yrs ago and I would never consider using it in an AR15, especially now since AR10's are more commonplace.

Mike
Mike, while I appreciate your comments, and I'll even take blame for pushing the conversation sideways, I'd like to get back on topic with this thread.

My goal is to push the AR15 platform as far as I can push it. I know it will never be an AR10. I also don't care. I know it will never be an F-class competitor either. Again I don't care. I want to see what is the best that can be gotten out of an AR15, with 'best' being defined as the most accurate for long range shooting. This is not a combat built, I don't care if I am limited to a small handful of rounds in the magazine. This is simply a gift to myself as a retirement present now that I have time to explore some possibilities.

So that said, how can I maximize the accuracy at long ranges from the AR15? I realize this may be expensive and futile.

The 6.5 Grendel is awesome, but seems to me it would be better if the velocity was higher and as I am not worried about carrying large amounts of ammunition in combat, then it would be reasonable to use a fat case and single stack them in the magazine.

The WSSM is a decent round, and probably about as powerful as can be stuffed into the AR15 action. But with longer bullets that have high ballistic coefficients you can't fit them into the AR magazines.

So that takes me back to pushing the shoulder back on the WSSM and using VLD bullets in either 6mm or 6.5mm.

Will it feed properly? Will I lose too much case capacity?

BTW, it also seems reasonable to cut a slot in the front of the magazine to allow for slightly longer bullets. Thoughts on that?

The 6.5 Grendel is right at the ragged edge for pressure when hand loaded in the AR now, in other words, "Why" try to go to a ctg that gives you more unusable powder space than you have with the Grendel? This is not the path to accuracy!

As to mag length, you are stuck with little enough as it is.

My problem with AA is they do not offer what I want in a barrel length in chrome-molly, and don't build the upper I want or I would be happy not to have to re-invent the wheel.

P.S. If you are shopping for accuracy and longevity, you don't buy barrels from people that make barrels, that don't buy a melt (50 tons) at a time. :confused:

This is simply a gift to myself as a retirement present now that I have time to explore some possibilities.

So that said, how can I maximize the accuracy at long ranges from the AR15? I realize this may be expensive and futile.

The 6.5 Grendel is awesome, but seems to me it would be better if the velocity was higher and as I am not worried about carrying large amounts of ammunition in combat, then it would be reasonable to use a fat case and single stack them in the magazine.

The WSSM is a decent round, and probably about as powerful as can be stuffed into the AR15 action. But with longer bullets that have high ballistic coefficients you can't fit them into the AR magazines.

So that takes me back to pushing the shoulder back on the WSSM and using VLD bullets in either 6mm or 6.5mm.

Will it feed properly? Will I lose too much case capacity?

BTW, it also seems reasonable to cut a slot in the front of the magazine to allow for slightly longer bullets. Thoughts on that?


You won't get any flak from me on being different and taking the road less traveled. Years back I had doubters that didn't think I could coax 1000+ HP out of 4.125" stroke SBC combination.


However...............

1. AR15-I think it's already been done; it's called the 65 Grendel, 6mmAR(Turbo) and the 6mm Hagar. All these smaller cases are very efficient and accurate for amount of powder that they burn.

2. 65Grendel- more grunt, why not install a 28" barrel unless you are too concerned about the "cool" factor.

3. WSSM- bigger isn't always better. It's about the most combustion efficient case that takes up the least amount of lateral real estate in an AR15 mag. Also, more often than not the most powerful cartridges of a caliber usually aren't synanamous with being the most accurate. Therefore, one has to find a balance.

The WSSM's are fairly wide at the shoulder when compared to the length of their powder columns, which is unlike a BR or PPC case. My initial thoughts are that the wider WSSM shoulder contributes to a greater amount of gas turbulence that decreases effciency, but what gets the case over is the brutal amount of powder capacity.

Therefore, if you have to push the 65 WSSM shoulder back just so you can seat bullet X to mag length, while decreasing it's core capacity and considering that existing viable cartridges exist, why not just do a 65Grendel or a 6AR Turbo with a 28" barrel?

Mike

First. I don't know.

Second, I'm asking you guys in hopes that you guys know!!! :D

As to barrel length, I have been looking at that and not sure where I will end up, but I know it will be nothing shorter than 26" is very reasonable, with 28" being possible too. Not looking for a cool 'entry' gun with tactical rails here. Looking for something big and heavy to shoot little targets far away.

Anything and everything is open for consideration as long as it will fit into or bolt onto an AR15 lower. I've got the lower. The gun will be built around that lower.

I believe the case for the WSSM is about the fattest case you can fit into the AR15 platform, anything with a smaller diameter would have a lower powder capacity. I do not have the case sizes for the 450 Bushmaster, but I believe the diameter to be well under the .555" base diameter of the WSSM. Not sure about the .284 Win, I know it has a rebated rim to bring the head size down to 308 size, but I don't know the case size.


.5 base diameter. The reason I am interested in it is that I trust Bushmaster quality control more, and there should be more meat in the bolt face and lugs.

Yes, it will lose capacity , but It should also feed more reliably.

How about .50 Beowulf case necked down to 6.5? I bet it'll be similar to WSSM case.

I believe the base of the 50 Beowulf is still narrower than the shoulder of the WSSM. The 50 Beowulf doesn't taper as much as the 450 Bushmaster, which would have even less capacity than the Beowulf. So the Bushmaster would certainly be ruled out as the case capacity of the 450 Bushmaster would simply give up too much and there are clearly better options, with the 50 Beowulf being just one of them.

I still don't understand the allure of the 450 Bushy, given its weak showing compared to the 458 Socom and also given the Bushy feeds handgun bullets. Sure there is plenty of hype that it is the round powerful enough to handle any big game in North America, but there is no way I'd want to face a brown, grizz or polar bear armed with the 450 Bushmaster. Not sure I'd want to even pop a moose with one either. The 458 Socom offers a far better selection of bullet weights for big game and duplicates the ballistics of a stoutly loaded 45-70.

As for the Winchester Super Short Magnum, I'm certainly open to using something different as the base case, but it is currently available for the AR15 platform, they seem to feed reliably, and they seem to function reliably. Magazine capacity is minimal because the fat cases take up so much room, but for a target rifle that is not an issue. I can easily live with magazines containing 3, 5 and 7 rounds. The biggest problem with the WSSM that I see is the need to seat bullets in too deep, which would then lead some to think that pushing back the shoulder would be a better answer, even if it gives up a little velocity.

Photo shows a WSSM AR bolt versus a 223 AR bolt http://i3.photobucket.com/albums/y75/melensdad/guns/1-2.jpg

Well I've been doing a lot of reading, especially about wildcat and benchrest reloading/shooting. And while I know that building a semi-auto AR15 at long ranges is a lot different than building a bolt action benchrest gun, there are some similarities that cannot be refuted or ignored.

What scares me about the wildcat is it may not feed well in a semi-auto and the only way to know if it will is to build one!

I guess I'm still leaning toward the 6.5 Grendel.

The single biggest complaint I hear about Winchester is that their brass is very inconsistent, and that may be one reason why the WSSM is not used as the basis for target shooting, or target wildcats. Laupa, on the other hand, makes the brass for the 6.5 Grendel and everything I read about their brass is that it is among the best of the best in terms of consistency.

Any thoughts :confused:

The single biggest complaint I hear about Winchester is that their brass is very inconsistent, and that may be one reason why the WSSM is not used as the basis for target shooting, or target wildcats. Laupa, on the other hand, makes the brass for the 6.5 Grendel and everything I read about their brass is that it is among the best of the best in terms of consistency.

Any thoughts :confused:

Winchester makes decent brass, but just like Remington not all cartridges are the same in quality.

The WSSM case necks are known for being excessively thick. However, if the core WSSM cartridge was all that spectacular then one could simply turn the case necks thinner, while making the thickness consistent to solve the brass issues. Simply, with the availability of so many proven .473 boltface target cartridges and plenty of .473 boltface factory and custom actions, the WSSM with it's magnum boltface just aren't that popular.

If you are going to be pushing the case shoulder back, most likely you are going to be turning the cases necks anyway, so the factory case neck thickness issues will be a moot point.



Mike

In my humble opinion optimum velocity for an assault rifle cartridge is between 2,300 and 2,450 fps. So in my opinion the next best step up from the 6.5 Grendel would be the 6.5mm BR.

I have been looking at other 22, 6.5mm and 30 caliber alternate cartridges too.

Bolts are one issue. Either rebate the rims to .443 or run a 473 bolt from the 458 socom. I talked to marty about it and after our discussion, I would not hesitate to run it at 52-55K. There are some people out there running some crazy nasty hot loads through the 458 socom. $90

The shells that seem to hold some promise are..........

WSSM - I was thinking about rebating the rim and running it at 52k

6.5x47 lapua - Trim it to 1.75 and it is almost short enough to run through an AR15 platform with light bullets. Personally I think it would work best as a 22x47 short shooting 50-60 grain bullets. Short bullets would be perfect for the short neck and OAL.

284 short like you mentioned. Short fat shell, good brass and a lot of work to form.

30 HBR too - another variant and a lot of form work. Probably about like a 6.5x47 lapua opened up to 308. I think some people that shoot HBR have been using the 6.5x47 shell as a base.

300 savage - really a tad too long. What a shame.

The BR family, 6.5mm br/brx/dasher, 30 BR all based on the 6mm BR shells.

The 6.5x47 short with a light bullet, 22x47 short, 6.5mm BRX, and the 6.5WSSM all look the best.

A 22x47 lapua short with a 53 grainer loaded at 2.3" would spit them out at 3600 fps at 52K or about like a 22-250. That would run through an AR15, but not sure how it would chamber.

I shoot the 30BR and that would be another good one but its a square case. You can get 2950 out of a 30BR with a 125 grainer run at max pressure out of a bolt gun. Very efficient cartridge.

The 6.5 brx with 123s loaded at normal feed lengths would only buy you about 150 fps over a hot grendel 123 load. Probably not worth the aggravation of fireforming etc.

The 6.5x47 with a 90 grainer would buy you 3100fps at 52k or around 200 over a 6.5G. Probably still not enough for the hassle.

A 6.5WSSM 123mk running on a rebated rim at 52K is starting to look a little better and would buy you 2850 fps or about 250-300 over a hot 6.5G load. A lot of work rebating rims. The brass is tough to form. Forget moving the shoulder back unless you do it in 15 steps with a car jack.

but....

Run it at 65K out of a oly upper and it starts looking better at 3050 and that is significant compared to the 6.5G, but it would have significant recoil too.

The real problem as I see it with maxing out the AR15 platform is the limit on pressure and the OAL. If you could run the 6.5x47 lapua at 2.5" oal max and at around 63k life would be grand.

Of course running at 2.5" is not doable without extensive lower mods and a special mag.

That said a 6.5 x47 lapua at 63k running at 2.5" and you could push a 123 gr MK at 2930 fps and a 140 gr MK at 2720 fps. Would drive a 155gr mega at 2500-2600 fps !!

Better yet just run the 6.5x47 out of an AR10 at 2.8" and with 140 MK at 2800 fps.

Overall I think the best AR15 option for a mega hot cartridge is just to let dtech build a 6.5 WSSM or one of his other WSSM variants to suit your needs although by the time you set that up you could almost have a .260 AR10.

If you can live with lighter bullets, what about necking up and blowing out the 7.62x45 Czech?

for example:

http://guntech.com/ammo/65_compare.jpg

After running a lot of bolt thrust numbers, the normal ar15 platform is just not up to it.

After doing that I felt like either an AR10 or a Oly arms WSSM upper would be the best choice to start with , or just have a dtech custom built but then you are still very limited on OAL.