09-27-2011, 07:30 PM
Brick,
Bwaites's 28" has a standard rifle-length gas system, which provides more dwell time. I would think that an extended gas system is more appropriate for a 28" pipe, since heavier bullets will create stresses on cases that wouldn't exist in a rifle-length gas 20"-24" system. There is one other area you need to check that can cause short-stroking, but I doubt this is your problem unless you've been in heavy rain or submersed your fire stick: The receiver extension tube screw has an air bleed/drain hole in it, which also holds the stock to the tube. If that is clogged, it can cause short-stroking in the system, since you now have a pneumatic recoil reduction chamber in the extension tube.
I would also try it with a standard rifle recoil spring, and standard 5.2 oz rifle buffer. After that, you might start looking at opening your gas port, which is probably the direction you'll go since the Grendel uses larger port diameters than the 5.56. Since you have an adjustable gas block, if you have a larger port on the barrel, you can still control it with your gas setting screw, so I wouldn't worry too much when it comes time to open the port. Also think about how you will need more gas flow in the winter, when the temps are lower.
As far as the Vihtavuori 500 series powders go, they are bad news for auto-loaders, and are known for eroding throats quickly. The velocities, while very fast, are often erratic, and I've seen crazy extreme spreads with them in my .260 Rem. Since you have such a long pipe and an extended gas system, you can benefit from slower powders.
Bwaites's 28" has a standard rifle-length gas system, which provides more dwell time. I would think that an extended gas system is more appropriate for a 28" pipe, since heavier bullets will create stresses on cases that wouldn't exist in a rifle-length gas 20"-24" system. There is one other area you need to check that can cause short-stroking, but I doubt this is your problem unless you've been in heavy rain or submersed your fire stick: The receiver extension tube screw has an air bleed/drain hole in it, which also holds the stock to the tube. If that is clogged, it can cause short-stroking in the system, since you now have a pneumatic recoil reduction chamber in the extension tube.
I would also try it with a standard rifle recoil spring, and standard 5.2 oz rifle buffer. After that, you might start looking at opening your gas port, which is probably the direction you'll go since the Grendel uses larger port diameters than the 5.56. Since you have an adjustable gas block, if you have a larger port on the barrel, you can still control it with your gas setting screw, so I wouldn't worry too much when it comes time to open the port. Also think about how you will need more gas flow in the winter, when the temps are lower.
As far as the Vihtavuori 500 series powders go, they are bad news for auto-loaders, and are known for eroding throats quickly. The velocities, while very fast, are often erratic, and I've seen crazy extreme spreads with them in my .260 Rem. Since you have such a long pipe and an extended gas system, you can benefit from slower powders.