11-25-2013, 05:10 PM
The reason why gas blocks and FSB's don't abut with the shoulder is because the gas port location was made with the intent of the handguards being captivated by a handguard cap. Since we don't really use handguard caps on precision rifles, they being free-floated, there is no usefulness to this dimension, unless someone wants to take a higher end barrel, and turn it into a service rilfe look-alike.
I personally lean towards the idea that mating the gas block up with the shoulder would probably be better for harmonics, and this is how I had GA Precision do my .260 Rem AR10. They profiled the shoulder to match the OD of the gas block OD as well, and it has a nice, blended fit, feel, and finish.
If I was profiling 18" and longer Grendel barrels that are clearly being used in free-float AR15's, I would get rid of the silly handguard cap space. Even if someone wanted to take their Jaguar and turn it into a Chevy, they could just machine down the rear flat of the military FSB and still make it fit just fine.
Some of the gas blocks will allow you to abut them to the shoulder, because their gas port hole is large enough to still cover the barrel gas port, even of the holes are not concentric to each other. If you do set up a gun like that, you then need to trouble-shoot the gas tube where it inserts into the carrier key, ensuring that everything still allows for the carrier to go into battery without binding on the gas tube flange.
I personally lean towards the idea that mating the gas block up with the shoulder would probably be better for harmonics, and this is how I had GA Precision do my .260 Rem AR10. They profiled the shoulder to match the OD of the gas block OD as well, and it has a nice, blended fit, feel, and finish.
If I was profiling 18" and longer Grendel barrels that are clearly being used in free-float AR15's, I would get rid of the silly handguard cap space. Even if someone wanted to take their Jaguar and turn it into a Chevy, they could just machine down the rear flat of the military FSB and still make it fit just fine.
Some of the gas blocks will allow you to abut them to the shoulder, because their gas port hole is large enough to still cover the barrel gas port, even of the holes are not concentric to each other. If you do set up a gun like that, you then need to trouble-shoot the gas tube where it inserts into the carrier key, ensuring that everything still allows for the carrier to go into battery without binding on the gas tube flange.