09-09-2023, 10:07 AM
mtn,
When you think about it, Blackout barrels have almost 30% more volume for the same length than Grendel (28.8%). This means gases have more space to expand and are quicker to lower in pressure. As the bigger diameter 30cal bullet heads down the barrel pressures in Blackout drop rapidly, and so pistol length gas systems have become the norm. When Blackout was first released it was all carbine length gas. That's about the only benefit Grendel has over Blackout in your project. Excess case volume is the big worry however.
Be careful of flashover. If there is only 50% of case space taken by either H4198 or 8208 loads it means when you fire horizontally (normal) the powder is not a column. If it is instead a larger surface area then the primer spit ignites more powder than normal, generating a spike of pressure. Larger primer holes and magnum primers will not help - probably make it worse.
Crunching the numbers, Benchmark is another powder that will likely work in your situation. Around 13 grains, but still only 46% case full.
When you think about it, Blackout barrels have almost 30% more volume for the same length than Grendel (28.8%). This means gases have more space to expand and are quicker to lower in pressure. As the bigger diameter 30cal bullet heads down the barrel pressures in Blackout drop rapidly, and so pistol length gas systems have become the norm. When Blackout was first released it was all carbine length gas. That's about the only benefit Grendel has over Blackout in your project. Excess case volume is the big worry however.
Be careful of flashover. If there is only 50% of case space taken by either H4198 or 8208 loads it means when you fire horizontally (normal) the powder is not a column. If it is instead a larger surface area then the primer spit ignites more powder than normal, generating a spike of pressure. Larger primer holes and magnum primers will not help - probably make it worse.
Crunching the numbers, Benchmark is another powder that will likely work in your situation. Around 13 grains, but still only 46% case full.