A Thales F90-based 21st Century 6.5mm Grendel +P Steyr AUG

[SHORT-N-SASSY]

I today E-mailed the following Message to Steyr Arms, Inc. C.E.O., Scott O'Brien:

"Mr. O'Brien,

Thank you for your encouraging response to my March 20, 2013 suggestion for a much-needed "heart transplant" for the 20th Century AUG: a multi-purpose 6.5mm Grendel-chambered Steyr AUG. To that end, I now submit for your consideration a suggestion for taking the new, large-diameter Barrel design (breech end) of the improved Thales F90, to its logical conclusion: increase the diameter of the Bolt head-Barrel Extension, while retaining the present diameter of the Bolt shank, to allow safe operation of higher chamber pressures for the Grendel --- operating pressures which have proven safe in 6.5mm Grendel Bolt-action rifles, with increased performance a result.

Remington Arms has used this technique in their 22-inch-barrelled .30 Remington AR-chambered R-15, to good effect: a rebated cartridge with a .308 Winchester rim diameter, in an AR-15-length action. Per Remington's ballistics chart for their best .30 RAR loading: 125-grain AccuTip BT bullet (BC=0.335) Velocity/Energy values of 2800 fps/2176 ft-lb, at the muzzle, and 1610 fps/719 ft-lb, at 500 yards.

Compare to 6.5mm Grendel +P load, in a 22-inch Bolt-action rifle: 139-grain Lapua Scenar BT (BC=0.615) Velocity/Energy values of 2700 fps/2250 ft-lb, at the muzzle, and 2020 fps/1259 ft-lb, at 500 yards. And, even from a compact 16-inch-barrelled 6.5mm Grendel +P-improved Steyr AUG, the 139-grain Lapua Scenar BT projectile leaves the muzzle at approx. 2550 fps/2007 ft-lb (surpasses the .30 RAR's 22-inch barrel slight ME advantage, by 100 yards), and retains 1895 fps/1108 ft-lb, at 500 yards.

I think it's fair to state that a 6.5mm Grendel +P Steyr AUG would be well-received.

Thank you for your consideration.

Sincerely,"

[Bill Alexander]

How would the weapon handle the recoil. Would the re acquisition of target and shot to shot times suffer.

I am somewhat cautious of increasing chamber pressures. The current 50,000 psi is a little low but is well suited to the case volume and the propellent types. There is ample buffer for cold weather pressure spikes. A revised figure of 55,000 psi would be perfect for the propellant but the parent platform would preclude this for durability reasons. Working from a 123 projectile the pressure increase would net around 64 fps velocity increase. Conversely the shift to a 139 projectile would drop velocity by 176 fps. The resulting cartridge is now over 100 fps slower. Note should be made that no adjustment is present for the longer 139 projectile an the extra intrusion into the case.

One of the most exhaustive albeit not formalized examinations of the weapon handling effects of the Grendel has been developed by LRRPF52.

[SHORT-N-SASSY]

How would the weapon handle the recoil. Would the re acquisition of target and shot to shot times suffer.

I am somewhat cautious of increasing chamber pressures. The current 50,000 psi is a little low but is well suited to the case volume and the propellent types. There is ample buffer for cold weather pressure spikes. A revised figure of 55,000 psi would be perfect for the propellant but the parent platform would preclude this for durability reasons. Working from a 123 projectile the pressure increase would net around 64 fps velocity increase. Conversely the shift to a 139 projectile would drop velocity by 176 fps. The resulting cartridge is now over 100 fps slower. Note should be made that no adjustment is present for the longer 139 projectile an the extra intrusion into the case.

One of the most exhaustive albeit not formalized examinations of the weapon handling effects of the Grendel has been developed by LRRPF52.

Bill,

Thank you for taking the time to chime in on this Topic.

First, it is my opinion that the AR-15 and the 6.5mm Grendel (in its present state of tune) make an outstanding team. Indeed, the latter was designed for peaceful cohabitation with the former: job well done! And, this is demonstrated throughout our Forum. That said, it is also my opinion that the 6.5mm Grendel is too good to be limited to just one auto-loading rifle platform.

And, I'm quite comfortable with your referencing respected 6.5 Grendel Forum Member, LRRPF52, in this matter. Fact is: it was the hard-earned experience and fact-based input that LRRPF52 and others contributed to the Forum that prompted me to join.

Just a couple quotes from LRRPF52 which relate to this Discussion:

1, August 12, 2012, Re Rebarreling a CZ 527 Carbine in 7.62x39 to 264 LBC, ". . . My buddy who has a 22" CZ527 Grendel is getting 2650-2700 with 139gr Scenars on top of N140, so you will be looking at muzzle velocities that are no longer limited by the 50K psi AR15 bolt. . . ."

2, February 9, 2013, Re necking down the .30 RAR to 6-7mm, ". . . Yeah. I think the RAR could be a family of cartridges in the AR15 that would serve target shooters and hunters alike, who are looking for longer-range or heavier pill performance, in addition to varminters. There is no need to do all the High Pressure Testing and MPI on the AR10 bolt, because it has so much mass, and was designed around the cartridge it was meant for, namely the 7.62x51 NATO. The AR15 bolt, receiver set, and extension was NOT designed around the 5.56 NATO, but the 50,000 psi limited .222 Remington. They never changed the geometry of the stress components, when they blew the shoulder forward and ramped up pressures to well over 50,000 psi for the .222 Remington Special, since the dimensions would have grown maybe .100", so they just left it as is, but then started realizing the need for Carpenter 158 versus 8620 on the bolt, and the whole HPT/MPI process to QC the bolts. I like that the RAR uses an AR10 bolt lug & face geometry, with an AR15 bolt body, enlarged outer diameter just behind the lugs to support them, and a larger extension to handle the hoop stress. . . ."

And, I've worked, extensively, with the AR-10: in the 1980's, with the Sudanese and Portugese AR-10's, and reporting on same in the AR-10'er; in 2001, successfully converting an American Spirit Arms .308 to the extremely satisfying .300 WSM.

Lastly, to those of us who would dare venture outside the 6.5mm Grendel-AR-15 comfort zone you have created, wish us luck!

[Nukes]

The AUG is chambered in 5.56 NATO. Are the 5.56 NATO chamber pressures also a durability problem?

I put thousands of mil-spec rounds through my AUGs without any problem other than shooting "weak hand." Was I missing something?

[SHORT-N-SASSY]

The AUG is chambered in 5.56 NATO. Are the 5.56 NATO chamber pressures also a durability problem?

I put thousands of mil-spec rounds through my AUGs without any problem other than shooting "weak hand." Was I missing something?

Nukes,

You may be aware that MSAR produced 7.62x39mm Conversion Kits for their 5.56x45mm STG-E4 (Steyr AUG clone), for a time. So, a Steyr AUG or a MSAR STG-E4 Conversion Kit (not interchangeable) for today's 6.5mm Grendel factory loadings, utilizing a proper Bolt and Barrel, should be good to go --- tinkering with the gas valve, as may be necessary.

However, today's E-mail to Steyr Arms is with respect to the improved Australia Thales F90, which now incorporates a large barrel diameter, at the breech end (unlike the rather slim OD of the present Steyr AUG/MSAR STG-E4, at the breech end) prompting my suggestion for consideration in chambering an "enhanced"/"+P" version of the 6.5mm Grendel cartridge, for the upgraded Thales F90 modified to include a larger Bolt head-Barrel Extension similar to the design incorporated in the Remington R-15 .30 RAR.

[Nukes]

Past tense? MSAR no longer produces the 7.62x39's?

It wasn't that long ago that I perused their website.

It looks like they too have been captivated by the .300 BLK: http://www.msarinc.com/products.html

I am pleasantly surprised that the 6.5 Grendel was not in Hornady's "temporarily suspended" list.

[LRRPF52]

Steyr has been working on a Grendel AUG since as early as 2008. One thing to consider with the AUG is looking at nations who issue it as their standard service rifle, and then look at what their special operations units are using in the same role. Australia comes to mind:

[Nukes]

Obviously a weapon that cannot be fired weak-handed has a serious impediment as a combat weapon. I am surprised that any army fields the AUG.

My profession and my nature are quite peaceful so, as a sport firearm, I would very much enjoy a 6.5 Grendel AUG. :-)

[LRRPF52]

I love the feel and handling of the AUG, but it needs a metal fire control group. Not sure if the newer guns have metal hammers, but anecdotal experience from Aussie soldiers seems to indicate that they had a lot of reliability issues with the AUG.

[stanc]

Obviously a weapon that cannot be fired weak-handed has a serious impediment as a combat weapon. I am surprised that any army fields the AUG.

What should be obvious is that it is NOT a serious impediment, judging by the lengthy and successful use in combat of rifles like the AUG and SA80.