Grendel II chamber

[JDub]

So Grendel II chamber = .264LBC chamber?

[bwaites]

So Grendel II chamber = .264LBC chamber?

Grendel II chamber = .264 LBC but with .300 neck.

Its really an LBC II since the unique thing about the Grendel is the compound throat and the Grendel II doesn't have it.

[rasp65]

Do you suppose Larry sent back all the barrels that were returned to Steve and had them "Scrapped"?

[LR1955]

As long as it is OK with the Mods, it would seem a reasonable idea to begin putting this info into a single location.* Hopefully, this will prevent the need for plowing through long threads that are largely about something else in order to find pertinent information.

As of early 2014, there is a lot of speculation about the performance of "Grendel II" chambers, some of which come with new barrels, others from the modification or "scraping" of existing ones.

Please include information about the barrel, including the manufacturer or similar info (like "Stoner"), type of chamber, whether is was sent out for modification.


Hopefully, it will be useful to get enough information to help owners of these barrels choose which factory loads are most likely to provide the best accuracy.** If it is discovered that these Grendel II barrels perform well with the same loads as the 6.5 Grendel SAAMI-spec ones, so much the better.


I hope that one of the Moderators will step in and let us know if this thread should include reloading info. WARNING: DO NOT EXCEED THE PARAMETERS OF LOADS TESTED AND PROVIDED IN RELOADING GUIDES OR BY MANUFACTURERS. Damaging your weapon or yourself can ruin your day and/or result in soiled underwear.



* This thread might be considered part of the 6.5 Grendel Ammunition and Reloading section, but we don't know yet if the Grendel II prefers certain bullets or factory loads.

** Of course not all barrels prefer the same loads, but this would be a place to start.

N:

What is this 'Grendel II' chamber? For all the years I have been involved with this cartridge, I know of two chamber designs. One was the conventional design with some leade and a taper. From my recollection of the Grendel history, this was the first chamber design Alexander used and found it to be lacking in terms of ability to handle different ogive types. So he came up with the compound throat which I believe is what he used in the patent issues that came up. The compound throat was what defined 'Grendel' so guys who didn't want to deal with Alexander to use the name, simply went back to the conventional throat design.

So, you may be calling the original design a 'Grendel II'.

I will say that I have been shooting both chambers for eight or more years and that the compound throat design is more forgiving in terms of accuracy for a variety of bullet ogives, just as Alexander intended. And that the conventional design -- what I think you are calling a 'Grendel II' -- is less forgiving but may give better accuracy with some loads.

Honestly though, it is as unlikely that anyone can come up with anything conclusive as it is that anyone on the Military forum will come up with an ideal military cartridge, or even bullet for that matter.

Also, I thought your question concerned factory loads? You put the handloading disclaimer in your post.

If this morphs into a handloading issue, as I am pretty sure it will, I will move it to the handloading forum is all. Not any big deal.

LR1955

[explorecaves]

LR1955: http://www.65grendel.com/forum/showt...ing-Grendel-II

Also, see the whole AR Stoner debacle with short throats....

[LR1955]

LR1955: http://www.65grendel.com/forum/showt...ing-Grendel-II

Also, see the whole AR Stoner debacle with short throats....

What is now called the .264 LBC with a .295 neck is (I believe) the original design. Alexander wasn't happy so went with a .300 and compound throat and the compound throat design is (I believe) what defined the Grendel in legal terms. Other companies couldn't stamp 'Grendel' on their barrels unless they had some sort of agreement with Alexander. So, they used the conventional design. LB, having to call it something, used .264 LBC. And yes, there were problems with early Hornady brass fitting some of his chambers. And yes, even though LB claimed that any Grendel factory load would chamber and shoot safely from his rifles, for a while some of the Hornady factory loads wouldn't chamber. I haven't heard of this for quite a while but it did happen.

And now Satern apparently has to call it something so they call it a 'Grendel II'.

I think my only point is that this chamber design is conventional and does not represent an improvement or something unique.

LR1955

[bwaites]

Shortly and succinctly, there are 4 designs:

Grendel: The SAAMI spec chamber with compound throat and .300 neck.

CSS/LW chamber: compound throat but with a .295 neck. CSS marketed these as the Match Grendel chamber if I recall correctly. I have been told LW and CSS will still cut this chamber on request.

LBC .264: Traditional chamber with .295 neck.

"Grendel II": Same as LBC but with a .300 neck.

I hesitate to call this new one "Grendel II" because I agree with LR1955 that what makes a Grendel unique is the compound throat. I really wonder why Saterns decided to call it "Grendel II" and why they didn't just use the .295 neck in the LBC. However that is for another thread.

Lets leave this one for loading information.

[nincomp]

LR,
If you have been able to avoid the recent big Liberty - Stoner - Saturn bruhahaha, count yourself lucky. To summarize, some members purchased new barrels that would not chamber some factory ammo or would show high pressure signs. Undersized throats were suspected, reamers maligned, tolerances questioned, names called and mud slung.

As it turns out, several years ago, Steve Saturn worked with PTG to make a variation of the Grendel with a straight leade and a 1.5 degree throat. Unlike the LBC-AR, it retained the Grendel's neck diameter of 0.300". The reamer drawing says "Grendel II."

As you suspected, it is likely to be pretty much the same as the original Grendel (no compound throat), but few of us have ever seen the that reamer drawing.

Based upon a quick look at the G II drawing the end of the 1.5 degree section is slightly farther into the barrel. This means that a standard Grendel compound throat (undersized or not), it can be reamed (or scraped, as Saturn calls it) to the Grendel II.

Grendel II.jpg

[dmsims21]

Do you suppose Larry sent back all the barrels that were returned to Steve and had them "Scrapped"?

He could write one of his "Short Stories" about the whole process.

[dmsims21]

Do you suppose Larry sent back all the barrels that were returned to Steve and had them "Scrapped"?

Did you mean scrapped or scraped?

[LR1955]

Bill / nincomp:

I got it and thanks for the info.

When these 'Liberty' and 'Stoner' barrels came out, no one knew who made them. That was enough for me to avoid them.

LR55

[NugginFutz]

I found this posted recently by Arne Brennan, one of the co-developers of the Grendel. It is a very candid assessment of what he referred to as the Grendel v1.0, now called the Grendel II by Steve Satern.

It should serve to enlighten any with questions regarding what the GII is capable of, and why Arne and Bill A decided to employ the compound throat in what we now know as the SAAMI Grendel.

Actually, the Grendel V 1.0 was a 1.5 degree .120 freebore. It worked well with Nosler 120 Ballistic Tips, Sierra 107 and 120 Matchkings and the Hornady 129 SST seated magazine. I still have a couple of the barrels sitting in my garage.

...

Some questions that have been emailed to me during the past few weeks:

...

So why the compound angle throat?

A colleague of mine and I took a few rifles out in May of 2004 and we were loading at the range. The Lapua Scenar did not shoot to our expectations with a .300" neck 1.5 degree .120 freebore when seated to magazine length. As we tested out and learned shooting other 6.5mm cartridges including the 6.5 PPC, 6.5 BR, 6.5x47 Lapua and 6.5-.284, the 108 and 123 scenar achieved their best accuracy with less than .005" jump to the lands. In a nutshell, the Compound Angle throat was a compromise to still let the Nosler 120 Ballistic Tips, Sierra 107 and 120 Matchkings and the Hornady 129 SST shoot well without generating unacceptable pressure levels and "trick" the 108 and 123 Lapua Scenar into shooting better.

Which will shoot better?

Depends what bullets you are going to shoot.

Will you notice a difference in accuracy?

Depends what level of accuracy you are capable of.

Will the removal of the .5 degree result in decreased chamber pressure?

Again, depends on the bullet, but I would not deviate from published load data and pump up the volume based on an assumption that the single angle .120" freebore will result in less pressure.

...

I would caution people not to try to push the heavier bullets because pressures can climb very quickly. Every person I saw who broke a bolt did so trying to shoot 130 grain and heavier bullets and trying to push them.

I remember shooting the 140 Partition at right around 2300 fps and that was about the practical limit without spiking pressure.

This all dovetails quite neatly with a posting here on this board.

http://www.65grendel.com/forum/showthread.php?8127-A-little-chamber-development-history

The short version? With mag length as a governing factor, certain bullets will not perform to their capability in a conventional .300" throat. That was why the compound throat was introduced. It allowed more bullets to be shot accurately when loaded at or less than magazine length. The GII is not a magic chamber, by any stretch of the imagination. Nor was the v 1.0 "better" than its successor, the 6.5 Grendel. It clearly had its own shortcomings.

While there is speculation that this variant will allow heavier bullets to be shot at higher velocities, there is no basis to this, given the above constraints. As a gas gun goes, there are just so many things you can do, before you start to exceed safe limits and start breaking things, or worse. You need look no further than the .264 LBC as proof of this. There are no quantum leaps in performance with it. Why, then, would a GII be able to achieve them?

As I previously stated, I believe that in the final analysis, whether this new (old) variant performs up to its maker's expectations, the net result is more demand for Grendel ammunition. That demand should translate into greater recognition in the industry and, hopeful, result in increased production of the ammunition. Everyone wins, as I see it.

ETA: The quote from Mr. Brennan was taken from the same site owned by the ex-member who has been promoting the GII for the last few months.

[bwaites]

stokesrj, whose opinion I deeply respect, has shot both chambers extensively, and if I recall his old posts correctly, he has found that both chambers shoot well, provided you select the best bullet for that rifle.

If you want ULTIMATE accuracy with any barrel, you have to work the load and bullet correctly.

I believe that the compound throat allows you to shoot more bullets with reasonable accuracy, as LR1955 has pointed out. Bill Alexander and Arne Brennan did a lot of work to find that chamber and for good reason. At one point I shot every single factory load into sub MOA groups with a SAAMI chamber. I suspect that I could repeat that with my SAAMI Grendels now.

I already know that I can't do that with the LBC 264 Black Hole barrel I have, but it does shoot factory Hornady into sub MOA groups and my handloaded Hornady into .75 MOA groups as well. I doesn't like my handloaded 107 Sierras, or 100 grain Bergers. It also won't shoot 123 Lapua Scenars, but that fits what Arne stated above.

[LRRPF52]

Projectiles with more of a secant ogive can get mis-aligned in the bore if they jump too much at Grendel pressures in the AR15. That kind of jump equals bad accuracy, unless you load tangent ogive pills as far out as the magazine will allow, like the 130gr Sierra Game King, the 85gr Sierra HP, pills like that. Then some will say, "Just drive the projectile faster into the lands with more pressure."

Ramp up the pressures, and the barrel tennon stretches too much. Arne even stated clearly that it's better to steer clear of the heavier 140gr pills in the Grendel, as pressure can sneak up on you quickly.

All this aside, when I look at SAAMI chamber performance through the scope at distance, I have zero reason to own a .308 any more, and have seen many people come to this same conclusion after being ardent holders to the .308 Win. Many will still keep both, but I personally have no reason to. That is a huge performance advantage to me that saves me literally thousands of dollars.

This .264 version 5.0 BS is just another way of people with a chip on their shoulder to try to ruin the cartridge. It's basically a knee jerk from short chamber to long chamber with all kinds of jump. If you look at the short chambered pipes, they consistently were shooting amazing little groups, blown and pierced primers aside, because the projectiles had no room to get off center, and the pressures are consistently higher, way beyond SAAMI Maximum Average Mean even (it takes a lot of pressure to blow or pierce a primer, usually 60-70ksi and higher depending on the primer).

The gun will take that a few times, but then things start to change permanently in the chamber if the bolt hasn't given out yet. The actual Grendel chamber is a fine balance between consistent accuracy across projectile shapes, and the rated pressures keep it safe. Some consider this "handicapping" the cartridge, and want to push the pressures more and more, but the real constraint is in the dimensions of the barrel tennon, barrel extension, and upper receiver which were all built around the .222 Remington. I don't think many people have a handle on how important it was for the engineers at Armalite to really make a lightweight rifle.

It has taken me a long time to realize the importance of the diameters, while looking past the strength of the bolt. It will be interesting to see what happens with the AR-Stoner/Liberty barrels that made it out into the market, as people build round counts on them. The ones that were blowing & piercing primers with factory ammo scream something wrong right off the bat, and will get immediate attention from all but the most unobservant mouth breathers.

...but the ones that really will be problematic are the ones that are short-chmabered, but still allow factory ammo to chamber and fire repeatedly at higher pressures than the SAAMI Maximum Average Mean (55ksi), not the Maximum Average Pressure (52ksi). You can fire factory ammo all day long at over 55ksi, as long as the bolt will take it (properly made bolts from good alloys will with a trued/squared system will do it for the life of the barrel), but will the chamber?

The walls are not that thick where the barrel tennon is. This is why we like to stay at 50,000psi. Delta tested the 6.8 SPC in high volume, and concluded it was dangerous because of this, and they have teams of engineers who are from aerospace backgrounds, who know materials strengths like the backs of their hands. You can't enlarge the chamber of the AR15 barrel (Reducing the thickness of the steel) AND ramp up or match the pressures of 5.56 NATO and expect everything to be peachy. I've said for years that even 5.56 is a shoe horn into the AR15-it was literally never meant for the 5.56 NATO, and I have seen plenty of 5.56 bolts broken, and broken one myself in a high volume gun at 10,000rds.

This chamber seems like an easy manufacturing approach, where a shop with poor QC can crank them out and let the reamer wear down, while not encroaching into the space for the projectile.

[NugginFutz]

Projectiles with more of a secant ogive can get mis-aligned in the bore if they jump too much at Grendel pressures in the AR15. That kind of jump equals bad accuracy, unless you load tangent ogive pills as far out as the magazine will allow, like the 130gr Sierra Game King, the 85gr Sierra HP, pills like that. Then some will say, "Just drive the projectile faster into the lands with more pressure."

I would have to agree with you there, LRRPF52. I found my BHW quite selective about what it liked. When working up the load it finally approved of, I discovered it had more dislikes than likes, with respect to the 123 Amax. I needed to really knuckle down and tune the load to find a node that was wider than .5 grains. Fortunately, I had shot an OCW with enough steps to spot it, and was able to go back and locate the sweet spot. Seating came next, which proved out that the tube liked them long. I believe that it would have been not nearly as tedious, had I been developing a load for a standard Grendel chamber. The data I collected while developing my load reminds me very much of the way a U-2 flies at operational ceiling. It's a 5 mph envelope, where flying any slower will cause a stall. Any faster and the wings go unstable. Not much room for error.