AR-15 in 6.5 Grendal: Thoughts/Experiences for perspective upgrade/build

[corym465]

The Grendel chamber is SAAMI and kind of like a 5.56 Nato as far as performance with a wide range of bullets. I haven't had any issues with the 264LBC which is kind of like a .223 Wylde. It prevents over working the brass and can be more accurate.

The .264lbc chamber was designed for the 123gr AMAX. The chamber can make it easier to find a pet load for 123gr AMAX and similar bullets. However, the chamber is no more accurate than the SAAMI and the SAAMI is no more accurate, in regards to the bullets mentioned. The gunsmith who chambers your barrel and the shooter themselves have orders of magnitude more impact on accuracy, in this comparison.

If these bullets are all you'll shoot, this is a great chamber. If you want versatility than the SAAMI, is the more accurate choice with a wider range of bullets.

The Grendel II is a chamber you should absolutely stay away from. And beware of these no name rack grade barrels. They can be great barrels. However, they've been known to have a short chamber, on occasion. This will cause you to jam ammo in the lands, causing pressure spikes. This can happen to any barrel with any chamber, it's just been seen more recently with the aforementioned barrels. It's caused by using worn reamers.

Your brass comparison is a apples to oranges comparison. The 5.56/Wylde are 60+ksi chambers, the Grendel/LBC are 52ksi chambers. If you stay within the SAAMI pressure limits, you'll be shocked at your brass life from either chamber. I know guys who have 20+ loadings on their Lapua brass from SAAMI Spec chamber, no trimming and no annealing.

[constructor]

The .264lbc chamber was designed for the 123gr AMAX. The chamber can make it easier to find a pet load for 123gr AMAX and similar bullets. However, the chamber is no more accurate than the SAAMI and the SAAMI is no more accurate, in regards to the bullets mentioned. The gunsmith who chambers your barrel and the shooter themselves have orders of magnitude more impact on accuracy, in this comparison.

If these bullets are all you'll shoot, this is a great chamber. If you want versatility than the SAAMI, is the more accurate choice with a wider range of bullets.

The Grendel II is a chamber you should absolutely stay away from. And beware of these no name rack grade barrels. They can be great barrels. However, they've been known to have a short chamber, on occasion. This will cause you to jam ammo in the lands, causing pressure spikes. This can happen to any barrel with any chamber, it's just been seen more recently with the aforementioned barrels. It's caused by using worn reamers.

Your brass comparison is a apples to oranges comparison. The 5.56/Wylde are 60+ksi chambers, the Grendel/LBC are 52ksi chambers. If you stay within the SAAMI pressure limits, you'll be shocked at your brass life from either chamber. I know guys who have 20+ loadings on their Lapua brass from SAAMI Spec chamber, no trimming and no annealing.

The Grendel II(really the Grendel 1) is the same as the original Grendel chamber before Lothar Walther suggested to Bill to use a compound throat. It was not designed for the 123 AMax because the 123 AMAX did not exist. The 264LBC chamber is the same as the Grendel II except that the neck dia of the 264 is smaller diameter than the SAAMI Grendel. The only difference in the SAAMI Grendel and Grendel II is a compound throat. My chamber was designed in 2007 long before the 123 Amax was made. I designed it for the Lapua 100 amd 107 SMK. Just so happens when the 123 AMAX and SST came out it was a perfect fit. It is very close to the 264 with the freebore being a little shorter in order to get the long ogive bullets closer to the lands.
The short chamber issues you speak of was because of a slightly small SAAMI Grendel chamber. The reamer was ground .001 under the minimum spec for the SAAMI Grendel. That made the throat very short because of the 1/2 degree throat angle used in the SAAMI Grendel chamber. IN spec Grendel chambers can vary as much as .137" in throat location because of the 1/2 degree throat and reamer spec of +.002"
Do you think that the neck of Grendel brass will not expand to the chamber walls even at 52,000 PSI? Do you think brass .012" thick will contain 52,000psi?
If so why are barrels made of stainless and CMV and the walls of the barrels 1/4" thick? The 264LBC and Arne's 6.5 CSS both have smaller neck diameters to keep the neck from expanding too much.
Bill, Grendelizer and Waites have all called the Grendel chamber a general purpose chamber even a machine gun chamber...General purpose and big like a 5.56. The 264LBC chamber is more like a match chamber with a smaller neck diameter and a normal freebore that is bullet diameter to align the bullet on the bore regardless of the OAL. The freebore is .264 dia. It doesn't matter where in the freebore a .264 bullet is it will always be centered on the bore. Where a freebore that is tapered like the Grendel the bullets must be within .010 of the .264 diameter of the lands to properly align. If not the bullet is laying on the bottom slope


from another forum-
The 6.5 Grendel was created by Alexander Arms, LLC and Arne Brennan, former head of Competition Shooting Sports, Inc.

Arne began development in 1998 with the goal to offer the range performance of the 7.62 NATO (.308 Winchester), but do so in the AR15 / M16 platform. As part of this development, flexibility in projectile weight and design was a major criteria as every caliber from .224 to .308 was evaluated. Selection of the 6.5mm caliber combined with our case design allows use of bullets from 85 grains to 144 grain in magazine length loadings. 6.5mm bullets provide high ballistic coefficients particularly in the 100-144 weight range with OTM bullets ranging in BC from .444 to .615. In comparison, the 77 grain Sierra in .224 has a .362 BC. In addition to OTM projectiles, there is an abundance of hunting projectiles from Nosler, Swift, Speer and Remington available that will operate magaizne length at respectable velocities that allow the cartridge to be used for a variety of game animals including deer, hogs and sheep. There are also FMJ projectiles in 100, 120 and 144 grain weights available in 6.5mm.

The case design of the 6.5 Grendel was born from the world record holding PPC family (22 and 6mm) of cartridges. Dr Lou Palmisano (Doc PPC), who became a friend of Arne Brennan, watched Arne's development work with great interest as a new variant of his cartridge designs showed its capabilities with higher projectle weights in a platform such as the AR15 / M16. The case for this family of cartridges were designed to be highly efficient combustion chambers that deliver incredible consistancy, often with velocity variations between shots in the single digits ( Consitent Velocity between shots is a major contributor to accuracy) The initial result of Arne's work became a 6.5 PPC optimized to work within the AR15 platform.

In 2002, Bill Alexander was introduced to Arne Brennan by Lothar Walther and Arne shared with Bill Alexander his work and performance obtained over many thousands of rounds of shooting. While the "Grendel" was unveiled in 2003 at Blackwater, the Grendel case was modified by Brennan, Alexander and Lapua into a production version best described a 6.5 PPC with a blown forward shoulder and shorter neck.

Case capacity of the Grendel is just over 35 grains of H20 with powder capacity within 5% of the 6 BR case. During development, a 6.5 BR AR15 was built and tested for many thousands of rounds. While the BR offered a slight increase in case capacity, the gain in velocity was insignificant. This insignificant gain in velocity, combined with the reduced magazine capacity (only 8 rounds in the space of a 20 round .223 Rem magazines), along with the extensive modifications required in the magazines made the BR case impracticle for the commercial market or any other volume user.

Testing and proof work have been underway to test the 6.5 Grendel in benchrest competition (the land of the 22 PPC and 6 PPC) and initial results are showing great promise of being competitive with the smaller caliber PPC family members. On March 6, 2006, Arne Brennan achieved a witnessed 1.198 inch 5 shot group at 660 yards using the Lapua 108 Scenar Projectile with N133 powder... no voodoo or black magic powder / bullets there. In addition, the 6.5 Grendel is being used or being developed in F-Class, Rifle and Handgun Silhouette and of course, High Power Rifle Competition. Further, the 6.5 Grendel is capable of making the 320 power factor (major) in 16-20 inch barrel AR's. With permission from the Commanding Officers, we are allowed to state that both the US Army Marksmanship Unit and US Air Force Shooting Team have match Grendel's which are in testing.

In January 2010, Les Baer discontinued offering "6.5 Grendel" branded products and launched the "264 LBC-AR" having worked with Hornady and Black Hills Ammunition to supply a complete product offering of Rifles, Uppers, Dies, Brass and Loaded Ammo. While Alexander Arms allows other manufacturers to use the "6.5 Grendel" brand under a licensing program, Les Baer has chosen to make it's cartridge "open source". As such, any manufacturer is permitted to use the "264 LBC-AR" chambering and branding without licensing or royalties. Competition Shooting Sports, who always offered a specialized chambering in its specific products, changed the branding of its products to "6.5 CSS" in 2006 so not to conflict with Alexander Arms products. As follow-up to Les Baer's release, Competition Shooting Sports has also released the availability of "264 LBC-AR" products. .

[corym465]

The Grendel II(really the Grendel 1) is the same as the original Grendel chamber before Lothar Walther suggested to Bill to use a compound throat. It was not designed for the 123 AMax because the 123 AMAX did not exist. The 264LBC chamber is the same as the Grendel II except that the neck dia of the 264 is smaller diameter than the SAAMI Grendel. The only difference in the SAAMI Grendel and Grendel II is a compound throat. My chamber was designed in 2007 long before the 123 Amax was made. I designed it for the Lapua 100 amd 107 SMK. Just so happens when the 123 AMAX and SST came out it was a perfect fit. It is very close to the 264 with the freebore being a little shorter in order to get the long ogive bullets closer to the lands.
The short chamber issues you speak of was because of a slightly small SAAMI Grendel chamber. The reamer was ground .001 under the minimum spec for the SAAMI Grendel. That made the throat very short because of the 1/2 degree throat angle used in the SAAMI Grendel chamber. IN spec Grendel chambers can vary as much as .137" in throat location because of the 1/2 degree throat and reamer spec of +.002"
Do you think that the neck of Grendel brass will not expand to the chamber walls even at 52,000 PSI? Do you think brass .012" thick will contain 52,000psi?
If so why are barrels made of stainless and CMV and the walls of the barrels 1/4" thick? The 264LBC and Arne's 6.5 CSS both have smaller neck diameters to keep the neck from expanding too much.
Bill, Grendelizer and Waites have all called the Grendel chamber a general purpose chamber even a machine gun chamber...General purpose and big like a 5.56. The 264LBC chamber is more like a match chamber with a smaller neck diameter and a normal freebore that is bullet diameter to align the bullet on the bore regardless of the OAL. The freebore is .264 dia. It doesn't matter where in the freebore a .264 bullet is it will always be centered on the bore. Where a freebore that is tapered like the Grendel the bullets must be within .010 of the .264 diameter of the lands to properly align. If not the bullet is laying on the bottom slope...

The SAAMI Spec is the original Grendel chamber. A lot of chambers were drafted in the development of the Grendel. It's called design and development. It does not make any of those chambers Grendel chambers.

The 264lbc is in no way close to being bastardized Grendel variant chamber Satern uses to cover their ass.

Your chamber??? The 123gr Amax and 264 LBC were designed in conjunction.

It isn't a matter of will the brass expand, it's at what rate from what amount of force.

The Grendel is a versatile chamber by design. If I was to build a Grendel Bolt gun I'd likely size the neck down to the 0.295", but not in a semi. The SAAMI Grendel is capable of better than 1/2 MOA. Why would I sacrifice reliability, when I can have it with a chamber that offers accuracy and reliability.

"Grendel the bullets must be within .010 of the .264 diameter of the lands to properly align. If not the bullet is laying on the bottom slope" :??? I've got a bartlein barrel from precision firearms that says this is hogwash. Being able to load 0.010" off the lands allows you to better tailor your load to your rifle. However, it's not required for superb accuracy.

[constructor]

The SAAMI Spec is the original Grendel chamber. A lot of chambers were drafted in the development of the Grendel. It's called design and development. It does not make any of those chambers Grendel chambers.

The 264lbc is in no way close to being bastardized Grendel variant chamber Satern uses to cover their ass.

Your chamber??? The 123gr Amax and 264 LBC were designed in conjunction.

It isn't a matter of will the brass expand, it's at what rate from what amount of force.

The Grendel is a versatile chamber by design. If I was to build a Grendel Bolt gun I'd likely size the neck down to the 0.295", but not in a semi. The SAAMI Grendel is capable of better than 1/2 MOA. Why would I sacrifice reliability, when I can have it with a chamber that offers accuracy and reliability.

"Grendel the bullets must be within .010 of the .264 diameter of the lands to properly align. If not the bullet is laying on the bottom slope" :??? I've got a bartlein barrel from precision firearms that says this is hogwash. Being able to load 0.010" off the lands allows you to better tailor your load to your rifle. However, it's not required for superb accuracy.

I think you need to line up all the Grendel/264 chamber prints side by side and look at them before making statements you know nothing about.
Are you saying Hornady developed the 123 AMAX for Les Baer and his 264LBC not the Grendel? Ask Dave Kiff where the design for the 264LBC came from. Why do the Grendel II and 264LBC both have .120" freebore? Why is every other dimension except the neck diameter the same on all cartridges including the Grendel?
Yep, my chamber design from 2007, like the 264LBC but has a shorter freebore close to Arne's chamber. Arne's chamber had a .292 neck, mine was .295. I didn't like the Grendel/6.5CSS chamber, I changed it to work better with the Lapua 100 Scenar and 107 SMK.
A couple of you have the opinion that the SAAMI Grendel chamber is better. My opinion like Les Baer's is the other chambers work better. The OP will decide if he wants a general purpose chamber like the Grendel or a match chamber like the 264LBC.

[corym465]

I think you need to line up all the Grendel/264 chamber prints side by side and look at them before making statements you know nothing about.
Are you saying Hornady developed the 123 AMAX for Les Baer and his 264LBC not the Grendel? Ask Dave Kiff where the design for the 264LBC came from. Why do the Grendel II and 264LBC both have .120" freebore? Why is every other dimension except the neck diameter the same on all cartridges including the Grendel?
Yep, my chamber design from 2007, like the 264LBC but has a shorter freebore close to Arne's chamber. Arne's chamber had a .292 neck, mine was .295. I didn't like the Grendel/6.5CSS chamber, I changed it to work better with the Lapua 100 Scenar and 107 SMK.
A couple of you have the opinion that the SAAMI Grendel chamber is better. My opinion like Les Baer's is the other chambers work better. The OP will decide if he wants a general purpose chamber like the Grendel or a match chamber like the 264LBC.

I made no mention of a Grendel/264lbc comparison.

No the 123gr AMAX was developed as a Grendel optimized bullet. I'm saying Les Baer had access to the 123gr AMAX being developed when the 264lbc was developed.

You know what they say about opinions and some smell worse than others.

[constructor]

I made no mention of a Grendel/264lbc comparison.

No the 123gr AMAX was developed as a Grendel optimized bullet. I'm saying Les Baer had access to the 123gr AMAX being developed when the 264lbc was developed.

You know what they say about opinions and some smell worse than others.

You and Paul Lrrpf52 repeat that crap like a broken record. Why would anyone designing a chamber for a certain bullet design the chamber so the bullet you say they designed it for has a .050 jump to the lands? You guys repeat that because you think it scares people away from the 264 chamber and toward the Grendel chamber. You think that is the only bullet that will work in that chamber. It shows how little you and Paul know about chambers. The 264 LBC chamber was NOT designed specificaly for the 123 AMAX, Sierra or Lapua. I'll bet you any amount of money Dave Kiff offered the first Grendel (developmental as you call it) reamer design to Les Baer just like he did me. The compound throat design was protected at that point. There were 3 designs being used in 2006. 2 had .120" freebore, the other the compound Grendel throat. The Grendel had a .300 neck dia and Arnes 6.5CSS version had a .295 neck diameter. ETC-Arne's first 6.5( before Bill A)had a .292 neck and an unknown freebore length, that was not a production chamber.
Short freebores are used with longer ogive high BC bullets. The tip of the bullet is loaded to a maximum length to fit in the mags. 2.28 or 2.30 depending on the mag. you take that length and work backwards to figure where the freebore should start. If you use a long nose high BC bullet the start of the freebore should be closer to the case. By telling everyone that chamber was designed for the Amax you all have been saying it's a better chamber for the high BC bullets and easier to load most bullets .010 off the lands where they have better accuracy.
My chamber has an even shorter freebore so the Amax, SST, 100 Scenar, 107 SMK when loaded to max length has a .010" jump to the lands, right where it should be. I can seat every bullet made 123gr and under(Except the Lapua and Sierra 123) .010 off the lands and use it at mag length.
The Grendel clan loves to talk about the high BC bullets. Why would you want a long freebore that allows the use of big round nosed blunt bullets when a shorter freebore allows everyone to set the bullets closer to the lands and get better accuracy?
You're right about opinions, some have their head so far up others asses they can't smell what they follow.

Unfortunately the OP is getting an ear full about a lot more than he asked for. OP, any real smith can make any rifle work. The gas system length isn't a problem, drilling the right sized port in the barrel shouldn't be a problem for someone that knows what they are doing. The only real problem I see is mags can be an issue but some have figured it out. They say 25 round mags work better than the others...they shouldn't but probably do. Tweaking the lips and spring of the mags to make them feed may take a few minutes. I don't use Grendel mags so I haven't had some of the problems that others do. Buying an upper to shoot long range accurately will be a little tougher than finding one good enough to hunt with. Lilja makes good barrels. learn to handload.

[corym465]

You and Paul Lrrpf52 repeat that crap like a broken record. Why would anyone designing a chamber for a certain bullet design the chamber so the bullet you say they designed it for has a .050 jump to the lands? You guys repeat that because you think it scares people away from the 264 chamber and toward the Grendel chamber. You think that is the only bullet that will work in that chamber. It shows how little you and Paul know about chambers. The 264 LBC chamber was NOT designed specificaly for the 123 AMAX, Sierra or Lapua. I'll bet you any amount of money Dave Kiff offered the first Grendel (developmental as you call it) reamer design to Les Baer just like he did me. The compound throat design was protected at that point. There were 3 designs being used in 2006. 2 had .120" freebore, the other the compound Grendel throat. The Grendel had a .300 neck dia and Arnes 6.5CSS version had a .295 neck diameter.
Short freebores are used with longer ogive high BC bullets. The tip of the bullet is loaded to a maximum length to fit in the mags. 2.28 or 2.30 depending on the mag. you take that length and work backwards to figure where the freebore should start. If you use a long nose high BC bullet the start of the freebore should be closer to the case. By telling everyone that chamber was designed for the Amax you all have been saying it's a better chamber for the high BC bullets and easier to load most bullets .010 off the lands where they have better accuracy.
My chamber has an even shorter freebore so the Amax, SST, 100 Scenar, 107 SMK when loaded to max length has a .010" jump to the lands, right where it should be. I can seat every bullet made 123gr and under(Except the Lapua and Sierra 123) .010 off the lands and use it at mag length.
The Grendel clan loves to talk about the high BC bullets. Why would you want a long freebore that allows the use of big round nosed blunt bullets when a shorter freebore allows everyone to set the bullets closer to the lands and get better accuracy?
You're right about opinions, some have their head so far up others asses they can't smell what they follow...

Nobody is trying to scare anybody off. Just providing the facts as they sit. If the facts upset you then so be it. The fact is real world data backs up what I have posted.

I've read enough of your gibberish to understand that if someone disagrees with your narrow understanding of things, then you attempt to label them as fools. You do this while running around claiming to be an engineer, while seeming to have a serious lack of understanding of physics and other basics of which an engineer's skills are based on.

[constructor]

Nobody is trying to scare anybody off. Just providing the facts as they sit. If the facts upset you then so be it. The fact is real world data backs up what I have posted.

I've read enough of your gibberish to understand that if someone disagrees with your narrow understanding of things, then you attempt to label them as fools. You do this while running around claiming to be an engineer, while seeming to have a serious lack of understanding of physics and other basics of which an engineer's skills are based on.

Yep, at 170,000 a year I've been fooling the crap out of them since 1984. Lucky that the Titans Stadium, 191Peachtree, 300 park ave, parts of universal Studios and Disney haven't fallen. Half of Atlanta and every ski resort in Colorado should be in shambles.
You said be sure to get the Grendel chamber, I said I haven't had any trouble with the 264LBC chamber. Then you opened it up but you can't explain with facts why the Grendel chamber is better. Provide us the facts as they sit . Give us some technical information(numbers) that shows why you think the Grendel chamber is better and better for what. Tell us where the part of the throat gets smaller than .264 and the lands start when the Grendel reamer is at the smallest in spec dimension and then where it starts at the maximum in spec dimension. Tell us how large in diameter the throat is just in front of the case in both situations. It takes about 5 minutes maybe 10. When the reamer is at maximum spec is there a force field holding the bullet up in the middle aligning it on the bore or is the cartridge, case and bullet laying in the bottom of the chamber? Take into consideration where the bullet is loaded in the case and where the full diameter of the bullet is in relation to the slope of the compound throat. I'll help you a little. This is a SAAMI chamber print. And check out the other one in my collection...look at that freebore!
Mods, sorry we're running this out but, it is kind of a learning experience.
http://www.saami.org/PubResources/CC...%20Grendel.pdf
65Grendel.jpg

[constructor]

I assume you wont answer with facts so I'll do it for you.
The SAAMI Grendel spec states the tolerance is +.002" different from most reamers +- .001"
Using the minimum SAAMI Grendel spec. .0178" in front of the max case length is the end of the cone and start of what we normally call the freebore the diameter is .2644"
The throat of a SAAMI Grendel tapers at .5 degrees. .023" in front of the cone the throat reaches .264 diameter and the lands begin to engrave the bullet. At .2635" in front of the cone the lands reach full height and the land to land diameter is .256" According to the SAAMI Grendel print.
When using a maximum diameter spec Grendel reamer (+.002)things change.
The diameter at the end of the cone is .2664" at .5 degree the bore does not reach .264 diameter until .137" in front of the cone. That is .114" further forward than the minimum spec reamer. That is like having a .137 freebore that is .0024" larger in diameter than the bullet. At .3775" in front of the cone the lands reach full height and .256" diameter.
Using the minimum spec reamer if you have a big blunt round nosed bullet it must be seated deep in the case to keep it from jamming into the lands .023" in front of the cone.
Remember the issues with bullets getting stuck in the lands on the Grendel forum a few months ago?
If using a Lapua 123gr Scenar .040" (.023+.017 cone length)of the full diameter of the bullet may protrude outside the case mouth and be very close to touching the lands.
However if the max chamber spec is used the same Lapua bullet must be seated .114" further out to get as close to the lands.
Considering same brand Factory ammo is all loaded the same length some bullets could be very close to the lands and some could be way off depending whether the reamer was at max spec or minimum spec.
A normal non compound throat chamber has a 1.5 degree throat. instead of having .114" difference due to tolerance they have 1/3 of the difference or .038". It also splits on the reamer spec +.001 or -.001. Lets say the 264 chamber has a design spec of .120. Due to reamer tolerance the freebore could be any where between .101 and .139" Kind of close to the max SAAMI Grendel freebore huh? Still much longer than the minimum spec Grendel. Now which one did you say to stay away from because it can cause pressure spikes? Now if JGS makes the 264LBC reamers the tolerance is half of PTGs or +- .0005" That reduces the freebore to a .019" difference min to max. .1105-.1295 for the LBC .0715-.0905 for my chamber...just about the same as mid spec of the Grendel but with a lot less movement of the lands due to tolerance.
I guess we could say a minimum spec Grendel chamber is good for High BC bullets like the Lapua, SMK, AMax and SST and not so great for blunt nosed bullets it could cause pressure spikes.
At the same time we can say a maximum spec Grendel chamber is good for blunt nosed bullets but not so great for long high BC bullets unless you load long and single feed them. One question, how do you know if you're getting a minimum spec or a maximum spec? A .023 or a .137" freebore?

[constructor]

A little more general info on the G. This is a post by Arne, the first guy to make a 6.5 on a PPC case.
The Grendel Version 1.0 as he calls it is the same as a 264LBC.

"TX65

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.

My previous 6.5 PPC chambers (had 2 of them) had free bores that were not known to even the reamer maker because I used a separate throating reamer. I do know that the reamer maker made an extra 4 reamers that had 1.5 degree .120 freebore throats because they thought that the cartridge would be of interest to handgun silhouette shooters.

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

What chambers have I had?

In addition to my original 6.5 PPC chambers (2 of them), I had a .295 neck compound angle (aka the 6.5 CSS), a .295 neck 1.5 degree with .120 freebore and lastly, multiple .292 neck 1.5 degree chambers with different free bores for different applications with the longest being .120.

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." end quote Arne



This is a list showing where the bullets will touch the lands in a Grendel II or 264LBC and as we see from above the Grendel V 1.0.
100gr. Nosler Partition OAL= 2.271
100gr. TTSX OAL= 2.330
100gr. Nosler BT OAL= 2.308
120gr. Hornady Amax OAL= 2.2575
120gr. Barnes TTSX OAL= 2.333
120gr. Barnes TSX OAL= 2.2945
123gr. Hornady SST OAL= 2.335
129gr. Hornady SST OAL= 2.380
129gr. Hornady SP Interbond OAL= 2.252
140gr. Nosler BT OAL= 2.316
140gr. Hornady SST OAL= 2.380
140gr. Nosler Partition OAL= 2.302
140gr. VLD OAL= 2.398

It's pretty clear to see the 264LBC, Grendel V1.0 or Grendel II was not designed for the 123 Amax or 123SST factory loads loaded to 2.25" but if you load them to 2.3" in a PRI mag you can get within .035" of touching the lands.