Is it possible to get 60,000 psi?

[RangerRick]

Saw a comment that Bill A. designed the Grendel case for 60,000 psi. Since the bolt is only rated for 50k, it's kind of a moot point.

But I got to thinking, we have to get a new barrel and bolt for Grendel anyway, why not design a 60k barrel extension and bolt combo that still uses the same bolt carrier.

I know that opens a whole can of engineering worms, but it made me wonder if there is even a good powder/bullet combo that would get you to 60k with the limited space in the brass and magazine.

If that is possible, what kind of muzzle velocities can you get with an extra 10k?

Does 20% higher peak pressure translate to 20% higher muzzle velocity?


RR

[bwaites]

Saw a comment that Bill A. designed the Grendel case for 60,000 psi. Since the bolt is only rated for 50k, it's kind of a moot point.

But I got to thinking, we have to get a new barrel and bolt for Grendel anyway, why not design a 60k barrel extension and bolt combo that still uses the same bolt carrier.

I know that opens a whole can of engineering worms, but it made me wonder if there is even a good powder/bullet combo that would get you to 60k with the limited space in the brass and magazine.

If that is possible, what kind of muzzle velocities can you get with an extra 10k?

Does 20% higher peak pressure translate to 20% higher muzzle velocity?


RR

20 doesn't equal 20. LRRPF52 has done the research on this and can fill in the numbers on hoop strength needed to increase nominal levels to 60k.

JASmith can run the numbers, but I would guess you might pick up 10% velocity.

[JASmith]

It is more like 5%:

95gr GS Custom bullet.

Per QuickLoad and an 18" barrel:

H335 50ksi 2724fps
60ksi 2874fps Increase 6%

Re 10X 50ksi 2710fps
60ksi 2819fps Increase 4%

[SHORT-N-SASSY]

Saw a comment that Bill A. designed the Grendel case for 60,000 psi. Since the bolt is only rated for 50k, it's kind of a moot point.

But I got to thinking, we have to get a new barrel and bolt for Grendel anyway, why not design a 60k barrel extension and bolt combo that still uses the same bolt carrier.

I know that opens a whole can of engineering worms, but it made me wonder if there is even a good powder/bullet combo that would get you to 60k with the limited space in the brass and magazine.

If that is possible, what kind of muzzle velocities can you get with an extra 10k?

Does 20% higher peak pressure translate to 20% higher muzzle velocity?


RR

RangerRick,

Welcome to the 6.5 Grendel Forum. I hope you find the following Links helpful:

http://www.65grendel.com/forum/showthread.php?3549-Is-anyone-currently-selling-a-60k-psi-bolt&p=38701&viewful=1#post38701

http://www.beyond556.com/bboard/forum/ar-variant-rifle/technical-library/4587-bolt-thrust-faq

"We shoehorned a bigger cartridge into the gun . . . Now impose a Grendel geometry and you are right at the tipping point." --- http://www.65grendel.com/forum/showt...ul=1#post75339

http://www.ar15.com/forums/t_3_121/573270__ARCHIVED_THREAD____Where_are_the_6_5_Grendel_guys__.html&page=1#i5517109

http://www.ar15.com/forums/t_3_121/573270__ARCHIVED_THREAD____Where_are_the_6_5_Grendel_guys__.html&page=3#i5559255

http://www.gunsandammo.com/wp-content/blogs.dir/2/files/sako-model-85-kodiak/sako8.jpg

[LRRPF52]

You would need a larger barrel extension and barrel thread tennon area, with a corresponding upper receiver. I had this same line of thinking back when I originally got into the Grendel, but over the years, and actually shooting the cartridge at distance, I don't see a lot of positives, and there are a lot of negatives.

For a bolt gun, it makes sense if you want to push the pressures, but with increases pressures comes throat life degradation as well. Right now, I would posit that the 6.5 Grendel offers one of the longest barrel lives of any modern factory chamberings when compared with .223 Rem, .308 Win., and any chambering that runs 55ksi or higher with a bottle necked cartridge.

The Grendel, as designed, hits a nice series of balancing points across the board:

* Lower pressure = longer throat life
* Lower pressure = longer brass life
* Lower pressure = longer weapon life
* Lower pressure = easier to balance gas & recoil system arrangement

When you look at it from the shooter's perspective, I basically get .308-like performance with a lot less pressure, a much lighter gun, ~50% of the recoil, and factory ammunition that is specifically meant to run in the AR15 gas system. Critics have called this "handicapping" or "putting a leash" on the Grendel, but they are looking for marginal increases in performance while losing the advantages of a lower pressure system.

If you want a .260 Remington in a gas gun, be prepared for a lot of challenges to overcome, and be prepared to only hand load for it. Mine spends most of the year in the case in my armory. My 6.5 Grendel's always go with me to the range unless I am only doing pistol work. It's just so much easier to shoot, work with, carry, case, load for, and buy ready-to-go factory ammo for.

I still love the performance of .260 Rem., but I am painfully aware of the headaches associated with it in a gas gun as well.

[RangerRick]

Hi SNS,

I've been around since 08. Got caught up in the last spam attack.

Thanks for the links. Great info!

RR

[RangerRick]

As I suspected. If it was that easy somebody would have already done it.

I can attest to the barrel life. My Grendel has nearly 6,000 rounds through it and is just starting to show loss of accuracy.

I tend to load near the max too.

Just from a mechanical perspective, I imagine that it would be tough to use the same carrier cam rotation with a new bolt/extensio.

RR

[sneaky one]

Ranger Rick, You have loads Posted In The Second Handbook ! Cmon dude! ????? .. Runnin Hott!

I Have moved on to Brass loads with JasMith., at a lower pressure - curve-speeds .. Just for fun for now- yet???i

[sneaky one]

Bill A, stated that the case is rated to 58,000 -L f2 stated this a long while ago. Don't injure oneself by going - Over the top..

How the deuce did your loads get in print?. I'll re check this ... oh man

[RangerRick]

Ranger Rick, You have loads Posted In The Second Handbook ! Cmon dude! ????? .. Runnin Hott!

I Have moved on to Brass loads with JasMith., at a lower pressure - curve-speeds .. Just for fun for now- yet???i

I'm not even sure what the 2nd handbook is. What is this in reference to?

I'm not aware that I ever contributed any load data to anything. I might have listed a few on here over the years. Maybe another Rick?

RR

[LRRPF52]

I'm not even sure what the 2nd handbook is. What is this in reference to?

I'm not aware that I ever contributed any load data to anything. I might have listed a few on here over the years. Maybe another Rick?

RR

We published 2 Reloading Handbooks, Volume II being dedicated to Hunting with the 6.5 Grendel, with a user listed series of data points for various powder, bullet, primer, and COL combinations in the back. There are many loads listed that were sourced from the forum, including your 130gr Swift Scirocco on top of CFE223 and LEVERevolution. Neither of those loads appear to be excessive. You can get them here: http://ar15buildbox.com/Sitemap.html

For example, Hornady lists a max load of 31.7gr of CFE223 under the 129gr SST, 129gr IB, and 129gr SP. Your 130gr Scirocco load was 31.5gr of CFE223 at 2.265" COL. Thanks, by the way, for being one of the early ones to work with that powder. Bwild97's tests with it really got my attention a few years ago, so I got a bunch and it is now my go-to powder for 123gr. 31.2gr gives me ~2500fps from my 16" Grendel, and is so accurate, a friend of mine cleaned a 500yd Know Your Limits plate rack his first time shooting the Grendel.

[sneaky one]

Thanks L-52, we have ranger rick up to speed.

[RangerRick]

We published 2 Reloading Handbooks, Volume II being dedicated to Hunting with the 6.5 Grendel, with a user listed series of data points for various powder, bullet, primer, and COL combinations in the back. There are many loads listed that were sourced from the forum, including your 130gr Swift Scirocco on top of CFE223 and LEVERevolution. Neither of those loads appear to be excessive. You can get them here: http://ar15buildbox.com/Sitemap.html

For example, Hornady lists a max load of 31.7gr of CFE223 under the 129gr SST, 129gr IB, and 129gr SP. Your 130gr Scirocco load was 31.5gr of CFE223 at 2.265" COL. Thanks, by the way, for being one of the early ones to work with that powder. Bwild97's tests with it really got my attention a few years ago, so I got a bunch and it is now my go-to powder for 123gr. 31.2gr gives me ~2500fps from my 16" Grendel, and is so accurate, a friend of mine cleaned a 500yd Know Your Limits plate rack his first time shooting the Grendel.

OK, thanks for that update. I've been out of the loop for awhile. Pesky job keeps getting in the way of my shooting!

I too, have had good luck with the CFE223. My previous favorite was AA 2520 I bought an 8 pound jug right before I discovered the CFE223, but the way things have been getting supplies I'm still glad I did.

RR

[bwaites]

2520 and BLC2 are still great powders for the Grendel, but we get infatuated with the new stuff!