The Firing Line Forums - View Single Post - Question about the "Shockwave" and short barrels

tpcollins · August 7, 2012, 01:28 PM

I got to thinking about the shockwave that occurs upon firing and I'm under the impression that it's about 18,000 fps. So I measure the barrels on my 22 3/8" .204, 16" .223 AR15, and 20" on my .243. I subtracted a cartridge length from each, divided that length by the fps I get from those loads, and deterimined the amount of time each bullet is in the barrel. Then I divided that length by 18,000 fps to determine one trip in the barrel. When I divide the shockwave time into the time the bullet spends in the barrel, I came up the the amount of times it would go back and force until the bullet exited the muzzle and found the following:

22 3/8" .204 Ruger - 6.64 times

20" .243 Winchester - 5.46 times

16" .223 Remington AR15 - 7.2 times.

The 16" .223 has the shortest barrel as well as the lowest velocity but it would seem to me it would be the hardest of the 3 to find a suitable load where the shockwave is closer to the breech rather than nearer the muzzle, since it's making more trips back and forth. Does this sound reasonable?

August 7, 2012, 01:28 PM	#1
tpcollins Senior Member Join Date: February 18, 2009 Location: SE Michigan Posts: 558	Question about the "Shockwave" and short barrels I got to thinking about the shockwave that occurs upon firing and I'm under the impression that it's about 18,000 fps. So I measure the barrels on my 22 3/8" .204, 16" .223 AR15, and 20" on my .243. I subtracted a cartridge length from each, divided that length by the fps I get from those loads, and deterimined the amount of time each bullet is in the barrel. Then I divided that length by 18,000 fps to determine one trip in the barrel. When I divide the shockwave time into the time the bullet spends in the barrel, I came up the the amount of times it would go back and force until the bullet exited the muzzle and found the following: 22 3/8" .204 Ruger - 6.64 times 20" .243 Winchester - 5.46 times 16" .223 Remington AR15 - 7.2 times. The 16" .223 has the shortest barrel as well as the lowest velocity but it would seem to me it would be the hardest of the 3 to find a suitable load where the shockwave is closer to the breech rather than nearer the muzzle, since it's making more trips back and forth. Does this sound reasonable? __________________ What direction did that last shot at Kennedy come from?