Supersonic cracks....

[86alaskan]

So I was toying around with some light for caliber loads in my 300WM this weekend. I was running a 110gr RN bullet at about 3500fps through my suppressor. I was also shooting my regular 185gr berger vld loads at 2900fps and noticed something strange. It seemed to me like the 110 load was noticeably louder than the 185. Does anyone know if I was experiencing pressure noise or if supersonic cracks get louder the faster the bullet goes?

 

[danny]

So I was toying around with some light for caliber loads in my 300WM this weekend. I was running a 110gr RN bullet at about 3500fps through my suppressor. I was also shooting my regular 185gr berger vld loads at 2900fps and noticed something strange. It seemed to me like the 110 load was noticeably louder than the 185. Does anyone know if I was experiencing pressure noise or if supersonic cracks get louder the faster the bullet goes?

The crack from rounds that are supersonic will be more authoratative as the speed increases. As rounds drop from supersonic towards sub-sonic, the crack will get less authoratative and then transition to popping sounds, then to weaker popping sounds. I would suppose eventually that you get to no sounds as the speed drops under the speed of sound.

Danny

 

[86alaskan]

i guess that makes sense. the difference was about 600fps or so, and the lighter faster bullet crack was VERY pronounced above that of the 185 load.

 

[XBBR Shooter]

Also, the level of sound is dependent on the disruption of the air (i.e. the formation of the pressure wave), and a round nose bullet is louder than a pointed bullet, at any given velocity.

 

[86alaskan]

XBBR, never thought of that, I would venture to guess that a round nosed bullet going way faster than a vld would most certainly be louder.

 

[Lapua40X]

If memory serves me (it always does but sometimes not as well as others) I believe that the shape of the mass has more influence than the speed - as long a every mass is traveling at sonic speed.

 

[86alaskan]

so given that, i suppose the space shuttle sonic boom would be more pronounced than an SR-71? seems like an appropriate shape comparison right?

 

[Lapua40X]

so given that, i suppose the space shuttle sonic boom would be more pronounced than an SR-71? seems like an appropriate shape comparison right?

NASA did some testing circa 2013 "NASA's Shaped Sonic Boom Demonstration" which revealed that an aircraft's shape affects the intensity of the sonic boom it creates at supersonic speeds. That would make your assumption correct that it's a fair comparison. Whether the SR-71's sonic boom would be greater than the space shuttle is however still open to doubt - remember, it's the shape of the mass not the mass.