A little chamber development history

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  • A little chamber development history

    www.alexanderarms.com phone#: (540) 639 8356

    Competition Shooting Sports, Inc can be found at www.competitionshooting.com : 770-889-9998

    Uppers and Barrel Kits are currently manufactured by both companies.

    Dealers:
    Competition Shooting Sports, CSS offers its own complete uppers and barrel, bolt & gas block packages in 6.5 CSS and 264 LBC-AR.

    Midway USA offers standard Alexander Arms uppers and supplies.

    Available Configurations: complete rifles or just uppers with barrel lengths of 14.5" 16.1", 19.5", 20", 24" and 28 inches ranging from mild to wild.

    Flash suppressors/muzzle brakes - The Tactical and GDMR series currently have flash hiders available. The GCS series by CSS has flash hiders on 16.1 and 20 inch models with compatibility for supressors.

    Magazines - Creative Products www.cproductsllc.com is currently selling 26 round stainless steel teflon coated magazines equipped with anti-tilt followers. A 17 round magazine of the same materials, albeit shorter, has also been released. 10 round magazines are made by Alexander Arms.

    Forends: Depending on configuration, the Grendel makes use of carbine, mid-length and rifle length gas systems with gas ports tuned to individual barrel lengths.

    Lower Receiver Compatibility: 6.5 Grendel uppers can be installed on any AR15 lower. No change is required to the lower receiver group.

    Buffers: The Grendel requires no change to the buffer system.

    Butt stocks, pads: Can use any buttstock offered for the AR15.

    Ammunition: Since 2004, Ammo and Brass have been available from Alexander Arms.

    At SHOT 2006, Wolf published their availability of 6.5 Grendel ammo offerings beginning with a 120 MPT and 123 SP loading. Ammo is scheduled to arrive in the USA in early Summer 2006. Wolf Ammo is brass cased, boxer primed and is reloadable with no modificaiton. Estimated price point per box is $5-$6 (20 rounds).

    Lapua has also entered agreement to sell and distribute Lapua headstamped brass and loaded ammo worldwide. While exact specs are unknown, my suggestion has been for Lapua to offer their 108 grain Scenar with a .478 BC. This loading can achieve 2600+ fps in a 16 inch barrel while operating at safe pressures. Also this would replicate trajectory performance of the 7.62 NATO with 168 grian bullets (24 inch barrel loadings)

    Les Baer contracted with Black Hills ammunition to produce ammo under the "6.5 Grendel" brand. In January 2010, Les Baer discontinued the "6.5 Grendel" brand and released 264 LBC-AR ammo produced by Black Hills Ammunition.

    15. What are the details of the all chambering options and names?
    Answer -
    “6.5 Grendel” .300 neck diameter with compound angle throat - Alexander Arms Chamber
    6.5 CSS” .295 neck diameter with compound angle throat for AR-15 rifles - Competition Shooting Sports / Lothar Walther Chamber in use since 2004.
    “.264 LBC-AR” .295 neck diameter with 1.5 degree throat for AR-15 rifles - Les Baer Custom Chamber - - Open Source Chamber - Contact Dave Kiff at Pacific Tool to obtain reamer
    “6.5 PPCX” .292 neck diameter with 1.5 degree throat for bolt action rifles only - Open Source Chamber - Contact Dave Kiff at Pacific Tool to obtain reamer - Chamber used to fire witnessed 1.18" five shot group at 660 yards using Lapua 108.
    "6.5 BPC" Special Purpose Bench Rest Bolt Action Chamber - Open Source Chamber - Contact Dave Kiff at Pacific Tool to obtain reamer
    Last edited by Guest; 02-25-2014, 06:17 PM.

  • #2
    part 2-
    Top Question Asked About The Grendel

    1. What will the 6.5 Grendel do that I cant do with a .223 Remington?

    Answer - The 6.5 Grendel extends the range capability of the AR15 platform and allows the AR15 to be used for ethical hunting of medium game such as Deer, Hogs and Sheep.

    2. Is the military doing anything with the 6.5 Grendel?
    Answer - Other then the items mentioned above regarding the USAMU and USAF Shooting Team with permission, Alexander Arms and Competition Shooting Sports never discuss military orders or discussions. If something is happening, it is up to the military parties involved to release that information.

    3. What is Grendel recoil like?
    Answer - The 6.5 Grendel recoils slightly more then the .223 Remington (Heavier Bullets = Increased Recoil).. However, calculations show the recoil to be 40-60% less then the .308 Winchester.

    4. The Grendel case is very straight, how does that impact feeding?
    Answer - Actually, the Grendel has more taper then a 7.62 NATO and the 5.56 NATO..

    5. Isnt a large rifle primer better then a small rifle primer for military purposes?
    Answer - The 5.56 NATO has a small primer and has survived for over 40 years. While it lacks terminal energy, the primer has nothing to do with this factor.

    6. The 7.62x39 has never worked well in the AR, why does the Grendel.
    Answer - First, the Grendel does not have as much case taper as the 7.62x39. The 7.62x39 due to its case taper requires a magazine with a pronounced curve (like the AK47) to work well. The AR15 with its mag well require a straight magazine section. The Grendel with its less pronounced taper then the 7.62x39 works. Second, Alx Arms designed new barrel extensions and magazines specifically for the Grendel.

    7. How does it perform in shorter barrels?
    Answer - The Grendel is a high efficiency cartridge and therefore burns its powder very well in short barrels. Barrels have been made as short as 12 inches with no problem. In fact, the 6.5 Grendel has already been used in handgun silhouette competition and won.

    8. How does the 6.5 Grendel perform less then 300 meters since it seems to be designed for beyond 300 meters?
    Answer - Yes, the 6.5 Grendel was designed for long distance shooting. However, the Grendel's projectiles dont magically appear at 300 meters and go the distance. Many people have had great success hunting deer and wild boar at close range. History is the ultimate judge and 6.5mm has been a proven hunting caliber for well over a hundred years even at moderate velocities.

    9. How do the bolts hold up?
    Answer - the only bolt that I have seen broken was one after 3000 rounds of excessive abuse running very high pressure loads (65,000 PSI). Even then, only one lug broke and the gun was back in working order with a quick 2 minute bolt swap. In 9 years of work on this, that is the only bolt I have ever seen fail.

    10. What if I need a replacement bolt?
    Answer - no problem, contact the manufacturer of your barrel for a replacement.

    11. I want to shoot 1000 yards with this cartridge, what should I do to set it up properly?
    Answer - When shooting at 1000 yards, you need to be sure your scope has sufficient elevation adjustment to correct for bullet drop. If you do not have a base with elevation built in, you need a scope with a minimum of 90 minutes of elevation (+/- 45 minutes). If you incorporate a 20 moa base, you can use a scope with a minimum of 50 minutes of elevation (+/- 25 minutes) although a scope with 75 minutes of elevation (+/- 37.5 minutes) will keep you out of the edges of the elevation adjustment range.

    12. What is practical range limit for different barrel lengths?
    Answer - While the cartridge will perform with 14.5 and 16 inch barrels, most people find that 18, 20 and 22 inches are the ideal barrel lengths for target shooting and hunting. Either of these 3 barrel lengths will allow medium game hunting out to 300 yards and allow accurate shooting to 600 yards. If you are going to be doing a lot of long range shooting beyond 600 yards, you should use a 28 inch barrel to extract as much velocity as possible.

    13. I will be hand loading my own ammo, what are the best bullets to consider?
    Answer - While many people are focused with 120+ grain bullets because of their ballistic coefficient, the best bullets to consider in cartridge of this size range from 81.5 to 108 grains. This lighter bullet weights will let you use a wide assortment of both ball and extruded powders and obtain respectable velocities at safe pressures. Bullets 120 grains or greater in weight are very powder choice limited compared to the lighter bullets.
    The 108 Grain Lapua can be safely loaded to achieve a trajectory match with the 7.62 NATO M118 LR round. For hunting, the Nosler 100-grain Ballistic Tip and Partition bullets are outstanding as is the Hornady 95 VMAX and Speer 90 grain TNT. Other bullets to consider include the Berger 85 grain flat base and Berger 100 grain HPBT.

    14. Why is the cartridge rated at 49,000 to 51,000 PSI in published load data? Cant the brass handle more?
    Answer - Because the AR-15 rifle is the main platform this cartridge was developed for, the rifle platform became the pressure-limiting factor due to its bolt/ locking lug design and bolt thrust limitations.

    Comment

    • BluntForceTrauma
      Administrator
      • Feb 2011
      • 3897

      #3
      Originally posted by woohoo View Post
      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.
      And who is claiming that Brennan worked with Alexander and Lapua to blow it forward?

      John
      :: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets

      :: I Drank the Water :: Revelation 21:6 ::

      Comment

      • NugginFutz
        Chieftain
        • Aug 2013
        • 2622

        #4
        Please - some citations would be nice.

        And thanks for the very interesting read.
        If it's true that we are here to help others, then what exactly are the others here for?

        Comment


        • #5
          It came from beyond 5.56. Arne could have written it.

          The Grendel and 6.5CSS go/no-go and field gauges are the same. That's how I knew the chambers were the same. The above says the CSS had a compound throat. My barrels did not look like a compound throat.
          Last edited by Guest; 02-25-2014, 06:57 PM.

          Comment

          • mongoosesnipe
            Chieftain
            • May 2012
            • 1142

            #6
            One thing I did not see which seems relevant given the current climate is the AA compound throat design which for all intensive proposes along with neck diameter is what separate the Grendel from other chamberings


            It is my understanding that the Grendel throat was modeled after the original 6.5x55mm swedish throat and was chosen because of the ability to shoot an extremely wide range of projectiles well obviously being modeled after a 118 year old design suggests that the compound throat is not exactly a new idea and if it was a design inherent to superior accuracy over all others it would be the dominant throat in bench rest shooting which it isn't

            The goal being a reasonably accurate chambering that could feed and fire anything thrown at it reliably 6.5x55 swedish and subsequently Grendel, not to say that there is anything wrong with a non compound throat they are certainly more popular than not and there are many Grendel clone listed above that shoot accurately and reliably with their traditional throats

            That being said the AA specified chambering has a compound throat
            Punctuation is for the weak....

            Comment

            • BluntForceTrauma
              Administrator
              • Feb 2011
              • 3897

              #7
              I'm not going to bother to argue, but from my ringside seat I'm going to give MAJOR credit for the blown-forward shoulder of the 65G case to Janne, the Finnish Lapua engineer, and the compound throat decision goes to Bill Alexander. But I understand no idea exists in a vacuum, both the Lee-Enfield and the Swedish Mauser, if I'm not mistaken, having compound throats.

              But I don't consider any of that to matter at this point. 6.5 Grendel is SAAMIed. If you want to label it such, please follow the specs exactly. Otherwise, do what thou wilt with wildcat permutations.

              John
              :: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets

              :: I Drank the Water :: Revelation 21:6 ::

              Comment

              • bwaites
                Moderator
                • Mar 2011
                • 4445

                #8
                Its a balanced, reasonable history, with only a very few nit picks.

                Comment


                • #9
                  The .303 Enfield and 6.5x55 Mauser have the shallow .5 degree leade, so they can handle a wide variety of projectile shapes. They are both known for having exceptional accuracy no matter what you do.

                  I think Bill combined that shallow leade with a standard target 1.5 degree throat, to make the Grendel's compound throat.

                  Comment

                  • BluntForceTrauma
                    Administrator
                    • Feb 2011
                    • 3897

                    #10
                    Ah! Thanks, LR.

                    John
                    :: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets

                    :: I Drank the Water :: Revelation 21:6 ::

                    Comment

                    • jawbone
                      Warrior
                      • Jan 2012
                      • 328

                      #11
                      fantastic collection of info. thank you, Sirs.

                      Comment

                      • BjornF16
                        Chieftain
                        • Jun 2011
                        • 1825

                        #12
                        Additional context to WooHoo's post...(Disclaimer: I don't "know" any of the players. I've never directly communicated with Bill Alexander. I've recently traded some emails with Arne Brennan. I own 2 "pre SAAMI" Satern barrels. I'm only filling in some gaps as I understand them.)

                        In 2000, Arne Brennan starts shooting what is a 6.5mm PPC having a tight neck (.292") with a conventional throat (having ordered a throat-less reamer in 1998 with separate throat reamer to experiment with designs). It apparently becomes a tack driver with 108 and 123 Scenars.

                        Brennan and Alexander are "introduced" in 2002. Apparently, it was a phone call Brennan made to Alexander with a dual purpose: discuss Beowulf and 6.5 project. A collaboration begins.

                        Alexander apparently didn't have a working gun in 6.5 yet, but had already been collaborating with Lothar Walther. It was LW that encouraged Brennan to contact Alexander.

                        It seems a lot of the collaboration was design tinkering between Alexander and LW, with testing done by Brennan. This may be a bit simplistic, as I'm sure Brennan would have made some inputs.

                        However, I've been told by Brennan (via email, matching what he wrote on the Beyond556 forum) that he was very unhappy with an early throat design in LW barrels delivered to him that incorporated an Alexander designed chamber/throat. This chamber had .300" neck and throat was apparently a traditional throat with long freebore in order to accommodate a wide range of bullets. It did not exhibit good accuracy over the wide range of bullets, in particular the Scenars (although Brennan admits it shot the 120 Nosler, 120 SMK, and similar bullets well). It was rejected by Brennan, and he apparently issued a recall of 10 of these LW barrels (I'm assuming built into uppers by him) and allegedly replaced them with his 6.5 PPC chambered barrels. According to Brennan, this includes two uppers sent to the US Army Marksmanship Squad for evaluation.

                        Alexander and LW went back to drawing board. Out of this came the compound throat that would achieve what a long freebore would accomplish (i.e. accommodate a wide range of bullets). I'm not sure how many iterations of this compound throat there would be before they settled on the current SAAMI spec.

                        Arne complained about low brass life of the 6.5mm PPC brass using .300" neck. He was getting only a few reloads. Reducing the PPC neck to .295 allowed him to get on the order of 10 reloads. So he went to a .295" neck.

                        Alexander collaborates with Lapua for brass. Lapua had a .338 based project they were working on and were looking for someone to build a rifle for their project. In discussing with Alexander, the 6.5 project was raised. Since Lapua's project was based off of .220 Russian case and Lapua made .220 Russian cases, they suggested a cost savings for the 6.5 project could be realized if they went with .220 Russian case instead of PPC since they could use their existing tooling. Case neck thickness was increased to address brass life issue raised by Brennan. This is when the 6.5 Grendel cartridge was born.

                        I've attached a David Fortier photograph of the original 6.5 PPC and 6.5 Grendel for comparison purposes. Are they the same cartridges?

                        I guess you could say the 6.5 Grendel is a variant of Brennans' 6.5 PPC. Out of 6.5 Grendel, we have 6.5 CSS, .264 LBC, etc.

                        IMPORTANT. Satern and Dave Kiff at PTG have allegedly been very critical of the compound angle throat. YET, we have recently learned that Brennan's 6.5 CSS chamber was essentially the Alexander/Lapua cartridge design complete with compound angle throat but with a .295" neck.

                        Question 1: If the compound angle throat was so "crappy", then why did Brennan go with the compound throat? Is it possible that it did what Alexander advertised it would do?...accommodate a wide range of bullets while maintaining accuracy?

                        Question 2: Since Brennan rejected the original .300 neck cartridge with traditional throat as being unsatisfactory, then why is Satern/PTG pushing essentially the same thing?

                        You decide.



                        Sources:
                        1. http://www.6mmbr.com/65grendel.html
                        2. http://www.rifleshootermag.com/2011/...del-evolution/
                        3. http://www.beyond556.com/bboard/foru...-december-2003
                        4. http://www.msrhunt.com/post/satern-a...71354?trail=30
                        5. Personal emails with Arne Brennan
                        Attached Files
                        Last edited by BjornF16; 03-05-2014, 02:39 AM.
                        LIFE member: NRA, TSRA, SAF, GOA
                        Defend the Constitution and our 2A Rights!

                        Comment


                        • #13
                          I can confirm much of this, particularly the developments with Lapua, as I personally know Janne, who was working on the .338 (8.6x39 Lapua Tactical) idea before Bill came to him, or he came to Bill at 2003 SHOT. The complaints we used to hear about split necks dates back to the PPC wildcats, which were necked up, so the necks were thin using 220 Russian brass.

                          Push those loads really hard, especially with the 130gr JLK's and you run into reduced life on the brass with the .300" neck, which is meant to function in self-loaders reliably, without having to full-length size your virgin brass before loading, like I have to with my .260 Remington.

                          The 6.5 Grendel is a well-engineered cartridge and chamber design, the result of a series of collaborations of several engineers with extensive experience with numerous cartridge and weapon designs. Looking at the history between Janne and Bill, you would have to spend several years of study to begin to grasp some of the things they have worked on.

                          It truly does have many fathers that contributed their own specialized piece of the pie to make the sum of the parts greater than the whole.

                          Comment


                          • #14
                            Here's a very detailed account from David Fortier:

                            "After founding Alexander Arms in 2001 he set-up shop at Radford Army Arsenal. Next he designed and placed into production the .50 Beowulf and an AR-15 chambered for the Soviet 5.45x39mm M74 cartridge. Then in 2002 he began brainstorming on what to do next. Eventually the 6.5mm PPC caught his attention as it would fit his existing high strength .50 Beowulf bolt. So he machined a solid brass 6.5mm PPC dummy round to ponder over. It seemed like a fantastic cartridge which was small enough to double-stack in an AR-15 size magazine. To test the concept, he built a rifle using a free floated 24 inch stainless steel match barrel with a 1-9 inch twist. He fed it using modified USA brand 7.62x39mm magazines. Initial testing revealed the small cartridge to have excellent potential.

                            Now the 6.5mm PPC was hardly new. It was simply a necked up version of the incredibly successful 6mm PPC Benchrest cartridge designed by Dr. Lou Palmisano and Ferris Pindell in 1975. After experimenting with it Alexander came to the conclusion that it was a logical solution for improving both the exterior ballistics and terminal performance of an AR-15. On August 13, 2002 Alexander was introduced to Arne Brennan. An avid High Power competitor, Brennan had built an AR space gun in 6.5mm PPC. They compared notes and Brennan became a vocal supporter of Alexander’s new project. However while Brennan was solely interested in long range competition, Alexander recognized the cartridge had much more potential. The problem was the lack of cartridge cases. Both Norma and Sako had ceased production of .22 PPC and 6mm PPC cases.

                            So at the 2003 SHOT Show Alexander approached Lapua’s US importer/distributor about doing a run of .220 Russian brass reformed into 6.5mm PPC. Unfortunately, with Alexander Arms being a small fish, they had no interest. He had hit a brick wall. Then fate stepped in when a stone-faced Finn in a typically European suite appeared at his booth. Janne Pohjoispaa, an engineer from Lapua, unfolded a piece of paper and handed it to him. Drawn on it was a new cartridge concept, the 8.6x39mm Lapua Tactical. It was basically a .220 Russian case necked up to .338, and Pohjoispaa was looking for someone to make a rifle for it. Alexander instead suggested necking the .220 Russian up to 6.5mm. When Pohjoispaa nodded the foundation for the Grendel was laid.

                            After the show Alexander began bouncing cartridge drawings off of Pohjoispaa. Initially these were almost identical to the 6.5mm PPC. Pohjoispaa though didn’t like the long neck due to production losses. So working together the two of them evolved the design into today’s 6.5mm Grendel. The first step was to shorten the neck and increase case capacity. With such a relatively small case, any increase in capacity was a plus. The final change was to thicken the case neck to .012 inch. This served to lengthen case life in a semi-auto rifle. Alexander Arms paid for the cartridge tooling and placed an initial order for 50,000 brass cases on 24 November 2003. About this time I asked Alexander what he planned on calling the new cartridge. “.26 Grendel,” he replied. Unimpressed, I suggested 6.5mm Grendel instead. He mulled it over, and the new cartridge was christened.

                            The finalized 6.5x38mm Grendel cartridge has a .441 inch diameter casehead and a case length of 1.524 inches. Rim thickness, at .059 inch, is significantly thicker than a 5.56x45mm. This aids reliability. Shoulder angle is 30 degrees and a small rifle primer is utilized. Overall cartridge length runs from 2.200-2.265 inches. 80 to 144 grain projectiles may be utilized, but it performs best with bullets in the 100-123 grain range. The result is a handsome little cartridge which fits neatly into the confines dictated by the AR-15's magazine well.

                            Due to its diminutive size one would expect the Grendel to be a purely short range number, like the visually similar 7.62x39mm. Such is not the case. Despite operating at low pressures and mid-range velocities, performance is surprising. Rather than trying to chase high velocities and dealing with high pressures, the Grendel case is designed to use very efficient projectiles. Efficient projectiles with high Ballistic Coefficients shed velocity and energy at a slower rate. Remember; it’s not the muzzle velocity which is important, but rather the retained velocity at your target."

                            Comment

                            • Drillboss
                              Warrior
                              • Jan 2015
                              • 894

                              #15
                              I put this diagram together in Excel to help me visualize what's going on in the Grendel's compound throat in relation to the grooves and lands. The dimensions are all taken from the SAAMI minimum chamber specs, and I think I got them transferred over correctly. Obviously, the vertical scale is greatly exaggerated to see the detail in the throat taper.

                              I thought this thread was as good as anywhere to post it.

                              Hope it helps.

                              Chamber Diagram.pdf

                              Comment

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