I and my Ear know what bullet snap-over is. The only time I personally ever get bullet crack-over is down here in the valley 'sometimes' in the winter days. about 3 hours ago and they were ALL 1033 to 1056 FPS. I just also dialed in a subsonic 30-221 powder-load in this week (by ear Only). (this next sentance I will tie-in latter). Also I take the same rifle to Idaho several times a year to over 3700-ASL and have never had a bullet ever crack over and POP either. ![]() I have been shooting for many years and I think I do know and can hear when there is, Bullet snap-over. All shots were below 1100 fps and bullets were quiet. I have Never had any bullets snap over and crack. (not just once) but During several trips over several years. 22 rimfire and eley club-x and agulaSE with 16" barrel and suppressor at 4500+ ASL in Moab Utah. bullet flight and the effects of bullet falling into unstable Transonic flight and going subsonic before reaching the target.ĭon't Know what to tell you 'But'. Then move back opposite into the world of Long-Range & extreme LR shooting and high Vel. Subsonic gets pushed less by wind and is superior even though the other that is going faster, moves flatter in projection. The bullet traveling sonic has to travel (something like) 1000+ fps faster to equal and surpass wind push effects in flight of the subsonic bullet. In comparison, Two bullets, one going super 1200 fps and the other going subsonic under 1099 fps. Subsonic is more efficient for being affected by wind push down range over high Vel. for bullets and the efficiency of subsonic bullet flight. And does not follow the general rule, is wind holds using Super & Sub. Nothing to do with (sub.crack-over) but some other weird science. You start dealing with gas pressure post combustion and friction of barrel length. It is the opposite as the barrel gets longer past the 16-18 inch in length using subsonic ammo. (for example) The longer the barrel, The more Velocity gained. Also using Subsonic ammo does not follow the Normal ballistic thought about barrel-length and Vel. The Higher you move ASL the chances for a subsonic round to break the speed limit Decreases. When I actually fired and keeping data found it Was Not the Truth or the Norm.Ĭant always believe what you read but I usually bank-on and put my money to true life experience. ![]() (for example) Vel.ballistic' Drop' of Zero POI as the temp. I have also read and heard things from the Sniper Manuals quoted that (IMHO) are not the truth in real life. air density and humidity are the same when it cracked-over before at Lower ASL altitudes.īullets and Science theory move in strange ways and I am No Rocket Scientist with a math major. I have also been told by people that are knowledgeable in this subject that this occurrence (of cracking over) will happen 'Less Often' as you raise up Altitude ASL when firing Subsonic. In real life This happens every year to me in the winter time. Even though in most user conditions it does not. It will MOVE FASTER and DOES leave the muzzle to crack the sound barrier. Will break over and crack the sound barrier at times. ![]() It 'Usually' fires under the 1100 fps mark and is not cracking BUT ammo that is Chrony and always shoots Sub-Vel. If you take that as fact, it would suggest use of bullets with velocities no greater than 975FPS at sea level when the intent is to travel to 5000 ft and retain performance below transonic which is approximately 1058FPS. Increase altitude to 5000 feet and given a 20degree temperature drop, Speed of sound will drop by ~44FPS and Bullet velocity will remain constant due to temperature offsetting the effect of altitude. According to my Army Sniper Manual, bullets fly faster as altitude increases, and as temperature increases. OR ~22feet per second.Įvery 20 degree drop in temperature lowers speed of sound by ~15MPH also. For every 5000 ft of altitude added speed of sound is reduced by ~15 MPH. The transsonic region is approximately 5% either side of the speed of sound. The one thing you will need to keep in mind is that there is increased noise generated in the transsonic region from buffeting of the bullet. There are a lot of variables in the equation, but in the end everything cancels out except the temperature. The variance with altitude is due to decreasing temperature with increasing altitude. According to the USAF Standard Atmosphere, the speed of sound varies with the square root of the absolute temperature.
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