Crack!, Bump!, or Puff!...Musings on Brakes/Acoustic devices

[LarryS]

For some time now I've been toying around with a 6 inch prototype cylinder attached to the end of my CR140, a .22 calib. airgun.

The shooting accuracy appears to be effected by these devices. Certainly by my variations in construction. To list the effects:

1) 6 inch cylinder with small exit hole just slightly larger than .22 - Sound is a "Bump!" Less than a Daisy Red Ryder springer. Pellets are accurate and group well with scope at 30 meters.

2) 6 inch cylinder with small exit hole just slightly larger than .22 and 3 rows of 5 small holes("Y" shape) over cylinder length. Slightly louder. Pellets are accurate and group well with scope but scope must be readjusted slightly in elevation.

3) 6 inch cylinder with small exit hole just slightly larger than .22, and 3 rows of 5 small holes("Y" shape) over cylinder length but a central partition with a medium sized hole is place in center of cylinder length. Sound is now a hard "Puff". But pellet grouping has dropped over an inch at 30 meters. Major change in scope elevation.

4) Removed cylinder. Cr140 sounds like a .22 smokeless powder rifle, in fact very close to a magnum .22 under a patio roof. Frightened or confused neighbors would call Police if it continued. I don't blame them either.... Pellet groups are FAR higher than ever before..... well over 2 inches and they smashed into the target backboard & logs with a loud "crack!".

To my mind this means the velocity of pellets thru any kind of chamber, brake, or acoustic device will likely reduce muzzle velocity, and grouping spread may be effected too. The difference between "with" and "without" is very dramatic...... in my opinion. -LarryS

[Joben]

To my mind this means the velocity of pellets thru any kind of chamber, brake, or acoustic device will likely reduce muzzle velocity,

...how do you figure that works?
Unless it's hitting something on the way out i realy don't see how something on the end of the muzzle would slow the pellet down.

I suggest you chrony or compare penetration.
(or were you the guy who made the ballistic pendulum like device?)

I very much doudt a silencer type device is making any significant change in muzzle velocity.
Though if it does i would be very much interested in hearing about it.

[sniper]

I would think that using a chrono would take the guessing work out.

I tried a couple different muzzle brakes on a 2250/24", it reduces the sound
by about 30% or more but muzzle velocity remains the same on chrono,
as without having one.

[ETA]

A 'shroud' will affect trajectory the same way as if a barrel weight is added to the front of airgun. The added weight will affect the reaction of the recoil and thus the POI. It is more pronounce on springers and on long distance shooting.
Other reasons the POI is affected are by too tight of a tolerance and you getting unequal 'surface drag' on one side of the pellet; or the pellet actually clipping parts of the shroud. This might also happen with mounting misalign.
A shroud should be permanently installed and zeroed with it install. Make sure the port tolerances are big enough to not be affected by bumps, handling and other minor variations.

[LarryS]

I am not completely sure of what is happening. I have checked and rechecked the close tolerance ports for traces of lead by misalignment. Those cases were corrected when found and were signified by a verticle AND horizontal deflection at the same time.

The dramatic elevation change ONLY is bothering me now. It seems to drop more with more suppression by the chamber.

I'll work on it some more and gather facts. My ballistic pendelum was dis-assembled from lack of use after original measures were made and the chrono device is now in two parts getting ready for the new remoted testing......Drat! I always regret cleaning up my workspaces for lack of proper room..... -LarryS