Muzzle Turbulence PB Applied to PCP?

[Troy Bakel]

Internal Ballistics:
1. High pressure air rapidly accelerates the pellet.
2. Air in front of the pellet is accelerated at the same rate as the pellet pushing it.
3. The rifling spins both the pellet and the air in front of it forming a vortex.

External Ballistics:
1. Air pushed out of the bore at high velocity by the pellet Impacts and penetrates the atmosphere immediately in front of the muzzle forming a cloud of turbulence.
2. Pellet exits the bore entering this turbulence while the high velocity higher pressure air behind the pellet, over takes the pellet adding to the turbulence.

3. Refer to:

4 . It appears, that a moderator would provide the cleanest, less turbulent transition from Internal Ballistics to External Ballistics than a standard barrel, a ported barrel, and maybe even a barrel with an air-stripper.

 

[dgeesaman]

Need to get those guys to shoot some more subsonics

 

[Troy Bakel]

Need to get those guys to shoot some more subsonics

I am sending them an email requesting High Speed video of PCP pellets and slugs!

Shot another 5 pellet group of 0.191" edge to edge with the Thomas, I want 0.189".

Think a moderator or air stripper may help. Asked Mr. Niksch what he thinks, waiting for a reply.

 

[Motorhead]

Had no idea how much disturbance is created pre-exit !! Some looks like leaked gasses going around projectile with others not so much.
A key take away ( Visually ) that the suppressed shots have little air disturbance pre or post exit ... Which does beg the question, How bad is the turbulence INSIDE the suppressor

 

[Troy Bakel]

Had no idea how much disturbance is created pre-exit !! Some looks like leaked gasses going around projectile with others not so much.
A key take away ( Visually ) that the suppressed shots have little air disturbance post pre or post exit ... Which does beg the question, How bad is the turbulence INSIDE the suppressor

The 45 ACP is an LSD trip. The gas blows by the round so fast post exit that the pressure waves are 100 % reversed with vacuum turbulence at the nose, then you can watch the pressure waves reverse back to normal as the round moves ahead of the gas.

As for what happens inside the moderator is an awesome guestion!

My next rabbit hole!

 

[thomasair]

I am sending them an email requesting High Speed video of PCP pellets and slugs!

Shot another 5 pellet group of 0.191" edge to edge with the Thomas, I want 0.189".

Think a moderator or air stripper may help. Asked Mr. Niksch what he thinks, waiting for a reply.

If this is something you care to pursue...the only way to satisfy that curiosity is to try.

I haven't found any type of air stripper to be helpful beyond reducing or eliminating recoil. Many claim they improve accuracy, though.

Mike

 

[Troy Bakel]

If this is something you care to pursue...the only way to satisfy that curiosity is to try.

I haven't found any type of air stripper to be helpful beyond reducing or eliminating recoil. Many claim they improve accuracy, though.

Mike

Thanks for your email response and the above response!

I treasure this rifle way too much to port the barrel or thread it, so a slip on moderator will be tried.

Which of course changes harmonics .....

 

[dgeesaman]

 

[Troy Bakel]

Wish the video was more frames per second!

I slowed the video to .25 speed, as such you can see more detail.

The air in front of the bullet seems to flow straight through while the gas behind expands into the first baffle slowing down and letting the bullet accelerate ahead of the turbulence.

 

[karl_h]

Had no idea how much disturbance is created pre-exit !! Some looks like leaked gasses going around projectile with others not so much.
A key take away ( Visually ) that the suppressed shots have little air disturbance pre or post exit ... Which does beg the question, How bad is the turbulence INSIDE the suppressor

For a light small subsonic projectile, depending on design of exit it can be noticeable. My .22 PB shooting using the mounts I had for my legal suppressor, noticeably harmed accuracy and it wasn't an alignment issue, my alignment was damn near perfect. My mounts are all compensators, that are primarily designed for reducing muzzle rise, so not symmetrical on gas handling. No suppressor and great accuracy, add suppressor and went downhill a bit. I had to get a couple mounts custom made for me that handled gas symmetrically and my accuracy came back. It was the gas pushing asymmetrically because of the compensator, and inside the suppressor that somehow made it bad on the 40gr 22's, the few 45 grain loads I had were less affected, but still a bit. Shooting without the suppressor attached to the compensator didn't bother it at all, only after installing the suppressor was it a problem. Probably opened groups close to 25% with the comp mount and suppressor, no problems with the symmetrical mount that bled gasses symmetrically. I'm sure it was more the gas behind the bullet than what was pushed out in front of the bullet, a lot more of it, and the gas gets in front of projectile long before the projectile passes through the compensator.

 

[nomojo65]

I will add a little to this topic, I have one of Mike’s FT guns with his shroud and have shot it with on and off haven’t seen any difference in accuracy albeit inconsistencies in pellets?
Now I realize this isn’t a true stripper “ maybe qualifies as one? “ Mike can better answer this.
I also like that his shroud does not touch the barrel so in no way does it affect harmonics of the barrel, although I’ve wondered if turbulence of air around the barrel might? I doubt I could ever tell this with the quality of pellets we have at our disposal!

 

[dgeesaman]

I believe that shrouds are superior to thread-on suppressors. For noise reduction, weight, and accuracy. The part I don't love about them is having to figure out how to clean the bore with one. On my TX200 there I found a brass tube that fits perfectly and better than a soda straw. On my Thomas FT it simply unthreads. My Anschutz ZM2002 is more complicated though.

 

[jps2486]

I agree completely. I have witness huge blasts of air ahead of the pellet as it exited the barrel. I can only assume this can affect it flight. While moderators absorb some of this energy it's main function is to reduce noise. I think an air stripper or muzzle brake in combination with the moderators would help improve accuracy. What about a test/development program Donny?

 

[jps2486]

I will add a little to this topic, I have one of Mike’s FT guns with his shroud and have shot it with on and off haven’t seen any difference in accuracy albeit inconsistencies in pellets?
Now I realize this isn’t a true stripper “ maybe qualifies as one? “ Mike can better answer this.
I also like that his shroud does not touch the barrel so in no way does it affect harmonics of the barrel, although I’ve wondered if turbulence of air around the barrel might? I doubt I could ever tell this with the quality of pellets we have at our disposal!

I agree that you haven't seen much difference in your FT gun, but don't forget, it's a .177 right and 20 fpe right? What I've seen is on .30 calibers pushing 100 fpe. There's a lot of energy to dissipate there.

 

[nomojo65]

I agree that you haven't seen much difference in your FT gun, but don't forget, it's a .177 right and 20 fpe right? What I've seen is on .30 calibers pushing 100 fpe. There's a lot of energy to dissipate there.

Not an engineer but because of the small volume of a .177 bore wouldn’t 20ftlb still effect the pellet leaving the barrel similarly?