Over-boring a .22lr barrel

[hardcorps]

A good, modern 22 can suppresses well on rifles even with bulk high velocity ammo.
Some of the 308 cans do some kind of voodoo magic because they work way better than they should for their size.
If you A-B a good, modern 22 can with bulk high velocity vs subsonic ammo you won't hear much difference, if any.

 

[Tolerent]

I have a single pump pellet rifle that boasts 1300 feet per second with light weight alloy pellets. When I do shoot the alloy pellets it came with there is a distinct and loud report. That report is more similar to the sound of a .22 rifle than it is to the sound of the same pellet rifle shooting a standard weight lead pellet. Based on that information I have to conclude that a well built and modern design silencer or suppressor is going to make it easy for me to tell the difference between a subsonic round and a supersonic round if the suppressor is part of the equation.

I might be able to agree with someone claiming that a supersonic .22LR exiting a good suppressor will not sound much different than the same bullet exiting a standard crowned barrel. But even there I anticipate the difference would be less than difficult to notice.

Anyway, this thread was not about the efficiency or value of a suppressor. It was about over-boring as a possible way to legally transition a 16.5" barrel to reliably reduce the muzzle velocity of standard inexpensive bulk .22LR ammunition. Then the issues of barrel distortion, bore misalignment, cleaning repercussions, and turbulence from escaping gasses passing the projectile in a tighter than typical bloop tube all came into play.

It has been an interesting exercise in mentally predicting outcomes that are better observed than predicted. The barrel is low value so ruining it is of little consequence and shortening it into a pistol barrel that is never allowed back on a rifle receiver after any failure as a bloop tube conversion, or simply throwing it away, would also be of little consequence.

Regarding the usefulness of a suppressor on:
1. Standard velocity supersonic .22LR I do tend to agree it is mitigated by the sonic crack. Still I would anticipate some easily noticed attenuation.
2. Subsonic ammunition I have witnessed the results of decent suppressors and have faith in the technology. Silenced... No. But quieter than closing a car door.
3. High powered high velocity rounds I have confidence the suppressor can knock the muzzle blast to a level where the sonic crack becomes the major report and that can be in the neighborhood of a 30AdB reduction. Still the remaining report at about 130AdB rather than the 160ish it started out to be is not silenced in any respect. But your ears won't ring after shooting a few rounds.
4. The 308 cans you noted above: Their special voodoo is subsonic loads. Something as easily obtained with a much cheaper 9mm carbine shooting 147 or 158 grain bulk ammunition.

 

[hardcorps]

I have many pellet guns, some of which do exhibit a supersonic crack when fired. Most are .22, though and getting 950-1000 FPS with a 22 pellet rifle is pretty strong. Also, have 9mm air rifle that will put a 60g pellet through a 2X4. Have a .308 air rifle that shoots cast 30 carbine bullets.
My 22 cal suppressor is from the lower end of the price spectrum but still tames the supersonic crack from bulk ammo. I have a chrony, a real time audio spectrum analyzer, and a few dB meters. I have not, however, set all the equipment up and made measurements. I am just speaking from experience. I've threaded many 10/22 barrels, many other AR style 22 semi auto rifles, and a bunch of 22 pistols. The short barrels on the pistols usually keep the high velocity ammo from supersonic velocities. The rifles and carbines experience more suppression than you would think, the supersonic crack is not there.
My point is before you go taking measures to lower velocity in a rifle or carbine you should try the suppressor and see where it can get you. If you want quiet pest control there are air rifles, some with suppressors that are called "moderators" or "lead dust collectors" or "noise dampers" that are very effective at short ranges and can approach 22LR capabilities.
As for the 308 vodoo magic, my buddy has a can that quiets standard 308 hunting ammo way more than you would think it could in such a small package. He's a dealer/manufacturer and has had many suppressors.

 

[john.k]

This is done with target type 32S&W autos ...holes in the barrel from just in front of the chamber ...round has to have a certain power at test,but not at gun muzzle ...sort of cheating ,but allowed ,and everyone does it.