Just an FYI:
The muzzle blast is (approximately) a point source. This means the sound decreases as the square of the distance. An observer at 200 yards distance will experience a sound level about 1/4 that at 100 yards.
The sonic crack is a line source. This means the sound decreases as the distance increases. An observer at 200 yards distance will experience a sound level about 1/2 that at 100 yards. However the longer the distance to the observer, compared to the flight path of the bullet, the more this line source acts like a point source. If you shoot into the berm at 100 yards and the observer is a thousand yards away, the sonic crack will be more like a point source.
It seems to me that if you are shooting at a fixed target, then just build a simple lengthwise shed with 45 degree (one in one) roof, and little to no sides (that is, just roof). This will deflect the muzzle blast straight down into the ground. However I think metal roofing is not a good choice as it transmits sound well.
The muzzle blast is (approximately) a point source. This means the sound decreases as the square of the distance. An observer at 200 yards distance will experience a sound level about 1/4 that at 100 yards.
The sonic crack is a line source. This means the sound decreases as the distance increases. An observer at 200 yards distance will experience a sound level about 1/2 that at 100 yards. However the longer the distance to the observer, compared to the flight path of the bullet, the more this line source acts like a point source. If you shoot into the berm at 100 yards and the observer is a thousand yards away, the sonic crack will be more like a point source.
It seems to me that if you are shooting at a fixed target, then just build a simple lengthwise shed with 45 degree (one in one) roof, and little to no sides (that is, just roof). This will deflect the muzzle blast straight down into the ground. However I think metal roofing is not a good choice as it transmits sound well.