05-15-2014, 02:46 AM
There is nothing inherently bad about the chamber. If it were in a bolt gun, it might allow longer bullets to be loaded, freeing up some case capacity for powder.
However, in the AR15, the longer throat isn't really useable because the overall cartridge length is determined by the magazine. Many of the longer bullets, which would probably see an advantage if they could be seated out longer, like being closer to the lands. Since you can't load them long because of the magazine, you can't get them close to the lands to make them accurate, either.
The chamber of the Grendel is fairly unique in designs used in the AR15, in that it has 2 angles into the caliber sized, engraved barrel. The first angle serves to help center the bullet, while the second eases the centered bullet into the bore. This design was used to allow the use of many different bullet designs and weights with the cartridge. Since all those bullets had different ogives, they all shot differently from standard chambers because of the great variation in length and amount of freebore in comparison to that length.
The chamber was a compromise, allowing bullets all the way from 85 grains to 140 grains to shoot well. Some spectacularly well. Some manufacturers have called it a "machine gun chamber" because it seemed so loose compared to conventional wisdom regarding accurate chambers. This tends to directly contradict what some seem to be experiencing with their barrels. However, it does seem to have achieved its design, allow good accuracy with all bullets in the weight group mentioned. Seldom do you hear anyone say, "I can't get this barrel to shoot anything well!"
Les Baer chose to go the other way, making a chamber with a somewhat tighter neck, (though still able to chamber factory ammo without difficulty when properly machined), and with a conventional throat. He wanted ultimate accuracy with either of 2 bullets, the 123 AMAX or the 123 Sierra HPBT. By all accounts, he achieved this with his chamber, so much so that he offers an accuracy guarantee shooting factory ammunition. Many others have used this chamber with good results as well.
The problem with the Grendel II chamber is that it doesn't use either method to effectively center the bullet, a tight neck OR a compound throat.
However, in the AR15, the longer throat isn't really useable because the overall cartridge length is determined by the magazine. Many of the longer bullets, which would probably see an advantage if they could be seated out longer, like being closer to the lands. Since you can't load them long because of the magazine, you can't get them close to the lands to make them accurate, either.
The chamber of the Grendel is fairly unique in designs used in the AR15, in that it has 2 angles into the caliber sized, engraved barrel. The first angle serves to help center the bullet, while the second eases the centered bullet into the bore. This design was used to allow the use of many different bullet designs and weights with the cartridge. Since all those bullets had different ogives, they all shot differently from standard chambers because of the great variation in length and amount of freebore in comparison to that length.
The chamber was a compromise, allowing bullets all the way from 85 grains to 140 grains to shoot well. Some spectacularly well. Some manufacturers have called it a "machine gun chamber" because it seemed so loose compared to conventional wisdom regarding accurate chambers. This tends to directly contradict what some seem to be experiencing with their barrels. However, it does seem to have achieved its design, allow good accuracy with all bullets in the weight group mentioned. Seldom do you hear anyone say, "I can't get this barrel to shoot anything well!"
Les Baer chose to go the other way, making a chamber with a somewhat tighter neck, (though still able to chamber factory ammo without difficulty when properly machined), and with a conventional throat. He wanted ultimate accuracy with either of 2 bullets, the 123 AMAX or the 123 Sierra HPBT. By all accounts, he achieved this with his chamber, so much so that he offers an accuracy guarantee shooting factory ammunition. Many others have used this chamber with good results as well.
The problem with the Grendel II chamber is that it doesn't use either method to effectively center the bullet, a tight neck OR a compound throat.
You seek escape from pain. We seek the achievement of happiness. You exist for the sake of avoiding punishment. We exist for the sake of earning rewards. Threats will not make us function; fear is not our incentive. It is not death that we wish to avoid, but life that we wish to live. - John Galt