Sonic boom/ air rifles/ and questions

[oldpro]

 I was entertaining a friend by breaking the sound barrier with my .25 cal. I kept cranking up the power and noticed the sonic boom was getting closer and closer. I was using pba platinum ultra light pellets and had the final tune over 100 fpe( with known settings and 43 grain pellets) and had a sonic boom right in front of the muzzle!!!! It was scary and caused the rifle to have a serious recoil. I stopped messing around because I began to think what would happen if it happens in the shroud? Would it blow the baffles and shroud apart? I don't know! But center fires go much faster and I've never heard of a sonic boom in a barrel before but I'm more concerned about in the baffles or shroud when the compressed forces are allowed to expand rapidly and cause the pellet to break the sound barrier. Maybe I'm being over cautious but it was kind of spooky and I didn't want to injure myself or my friend. So the question is can you have a sonic boom in the barrel or shroud and if so is it dangerous.

[Motorhead]

Travis,
While generally we don't shoot our AG's in the supersonic range velocities, the actually event that is the sound barrier and sonic crack it creates is NOT one of changed pressure or volume.  It is that of acoustics and in that no blowing apart of a shroud or such stuff likely to occur.
I periodically shoot Felt Cleaning pellets from the PCP's. This CRACK upon shooting and it happens right at the muzzle, while it startles you to be sure ... it is just sound and nothing more.

JMO,
Scott

[oldpro]

Thanks Scott! I was pretty sure that was the case But The force I felt was real and had more than sound to it , it caused the gun to recoil very hard and really got me worried even though I've never heard of even one case of this kind of failure. I'm sure it would of happened by now but I don't want to earn the Darwin Award any time soon lol.

[Bill G]

The Darwin award...... LOL.  I love those.  Could there have been a contamination of a substance that might have combusted?

[rsterne]

I have pushed pellets supersonic many times, my personal record is a 12 gr. Laser in .22 cal at 1344 fps.... The interesting thing is how quickly they slow down at those speeds, it is subsonic again before reaching 10 yards.... The additional recoil you noticed is a progressive thing, caused by the additional FPE generated not only by the pellet going faster, but more by the vast increase in air required to launch it.... It may take 3 times the air to go supersonic than it does to drive the same pellet at 1000 fps, and that air has a surprising amount of mass and FPE.... In fact, the FPE generated by the air in that 1344 fps shot was nearly as much as from the pellet.... Since the efficiency really drops.... and hence the amount of air and the recoil it produces really increases, once you go supersonic.... you notice a pretty dramatic increase in recoil and muzzle blast.... I suppose it is possible for that vast increase in the amount of air to dislodge a baffle that wasn't strong enough.... but I would think it unlikely in a properly designed LDC....

Bob

[oldpro]

   Is it possible the shockwave from the sonic boom right in front of the muzzle prevented some air from escaping and drove the rifle back at me? Thats what it felt like, I have pushed this rifle past 120fpe before and never had this same recoil effect though I was shooting very heavy lead subsonic at that time.

[RFC]

This is what's happening inside your barrel.

http://www.privatejetscharter.com/photos/photo/95#

[garczar6]

That pic of the F-18 is spectacular.

[rsterne]

Actually, inside the barrel, at the higher pressures involved, Mach 1 is higher, so it is very unlikely that the air is flowing supersonic until it exits the barrel and the pressure drops.... so you aren't seeing that spectacular shockwave inside the barrel like in the photo of the F-18.... There is a big difference in pushing a heavy bullet at 120 FPE subsonic and trying to push a lighter one supersonic at the same FPE.... The drastic decline in internal efficiency as the velocities approach and exceed Mach 1 require the valve to be open right until the bullet exits the muzzle, meaning more air is released relative to the bullet weight.... It is possible that the backpressure inside an LDC might increase the recoil when past Mach 1, not having used one (they are illegal in Canada) I can't speak to that.... However, the increase in recoil when you try and push a pellet supersonic is something I am quite familiar with, having experienced it many times....

Bo

[Mod90]

So Bob, how often/have you ever experienced muzzle flip when shooting airgun pellets/bullets supersonic?

[rsterne]

Muzzle flip?.... Most rifles have a small amount of muzzle rise on recoil, and the greater the recoil energy the greater the rise.... However, it's nothing compared to what you see in a handgun.... I built a .30 cal 2250 HPA that shot 45 gr. pellets at 490 fps (24 FPE), and it had noticeable "muzzle flip".... When you start playing with air rifles over 100 FPE, which is .22LR territory, you can certainly feel the recoil.... and when it more than doubles, such as happens when you push from 1000 fps to 1200, the difference is very noticeable.... Heck, you can tell the difference between .22LR target loads and HV loads, right?.... at least I can....

Bob

[Matt15]

Muzzle flip?.... Most rifles have a small amount of muzzle rise on recoil, and the greater the recoil energy the greater the rise.... However, it's nothing compared to what you see in a handgun.... I built a .30 cal 2250 HPA that shot 45 gr. pellets at 490 fps (24 FPE), and it had noticeable "muzzle flip".... When you start playing with air rifles over 100 FPE, which is .22LR territory, you can certainly feel the recoil.... and when it more than doubles, such as happens when you push from 1000 fps to 1200, the difference is very noticeable.... Heck, you can tell the difference between .22LR target loads and HV loads, right?.... at least I can....

Bob

My .25 Uber Pumper at 786 FPS (35 FPE) has a small amount of recoil.