I agree, the Blackout is more suited to this dual supersonic/subsonic capability than the Grendel.
The .30 cal Blackout has less space to fill with powder than the Grendel; 25grains H20 space compared to the Grendel's 35gns. The bullet choice is also heavier; up to 240 grns in .30cal compared to 160gn in 6.5mm. Both of these make loading for subsonic easier and less dangerous. There is less chance of flash-over or secondary-explosion-effect (SEE) from partially filled cases.
Taking the earlier stated Grendel load of 13.3gns of A2015 with a 160gn projectile and running the numbers, even pushing the bullet back as far as is reasonable (say, 2.12" OAL) you still get only 57% case capacity filled. Anything less than 80% and you have to start worrying about it being dangerous. Trail Boss is about the only powder I know designed to be high-bulk, low-pressure. But you fill the case and get safety at the expense of cycling and perhaps even low subsonic speeds.
As for low subsonic, given the supersonic crack starts at about 90fps below the sound barrier and gradually builds to its loudest about 100fps beyond the sound barrier a round travelling at 800-900fps would be quieter than the same round at 1,000fps, even though they are both subsonic. Plus there's not much difference in drop between 900fps and 1000fps at 100M, and let's face it, that is about as far as subsonic is practical.
Hornady's subsonic Blackout load is their 208gn AMax bullet. They've taken an off-the-shelf supersonic match bullet which was never designed for flesh, no doubt because it saves them money, it is the right weight, and the most reliable feeding (pointy tip). Perfect for punching paper.
Again, I have to agree, it is all about supply and demand. There's just not enough demand for the real thing in the civilian market. And when Hornady's SS paper-punching ammo is half the price of LeHigh's SS specialised flesh ammo which one are the majority of civilians going to choose?
One more edit... A typical supersonic Blackout projectile is 110-125gns whereas a subsonic is 200-240grains. You are doubling your ammunition weight for no more ability to kill (probably less). The only benefit subsonic ammo gives you over supersonic is sound. It has to be a real specialised need to use subsonic before it offsets the downsides; the extra weight, and the severely compromised effective range, and the cost. This assumes you've solved the potential danger of flash-over and you believe a subsonic round is no less deadly than a supersonic rd...but it is quiet! Well, not 'Hollywood' quiet but you know what I mean, quieter.
The .30 cal Blackout has less space to fill with powder than the Grendel; 25grains H20 space compared to the Grendel's 35gns. The bullet choice is also heavier; up to 240 grns in .30cal compared to 160gn in 6.5mm. Both of these make loading for subsonic easier and less dangerous. There is less chance of flash-over or secondary-explosion-effect (SEE) from partially filled cases.
Taking the earlier stated Grendel load of 13.3gns of A2015 with a 160gn projectile and running the numbers, even pushing the bullet back as far as is reasonable (say, 2.12" OAL) you still get only 57% case capacity filled. Anything less than 80% and you have to start worrying about it being dangerous. Trail Boss is about the only powder I know designed to be high-bulk, low-pressure. But you fill the case and get safety at the expense of cycling and perhaps even low subsonic speeds.
As for low subsonic, given the supersonic crack starts at about 90fps below the sound barrier and gradually builds to its loudest about 100fps beyond the sound barrier a round travelling at 800-900fps would be quieter than the same round at 1,000fps, even though they are both subsonic. Plus there's not much difference in drop between 900fps and 1000fps at 100M, and let's face it, that is about as far as subsonic is practical.
Hornady's subsonic Blackout load is their 208gn AMax bullet. They've taken an off-the-shelf supersonic match bullet which was never designed for flesh, no doubt because it saves them money, it is the right weight, and the most reliable feeding (pointy tip). Perfect for punching paper.
Again, I have to agree, it is all about supply and demand. There's just not enough demand for the real thing in the civilian market. And when Hornady's SS paper-punching ammo is half the price of LeHigh's SS specialised flesh ammo which one are the majority of civilians going to choose?
One more edit... A typical supersonic Blackout projectile is 110-125gns whereas a subsonic is 200-240grains. You are doubling your ammunition weight for no more ability to kill (probably less). The only benefit subsonic ammo gives you over supersonic is sound. It has to be a real specialised need to use subsonic before it offsets the downsides; the extra weight, and the severely compromised effective range, and the cost. This assumes you've solved the potential danger of flash-over and you believe a subsonic round is no less deadly than a supersonic rd...but it is quiet! Well, not 'Hollywood' quiet but you know what I mean, quieter.