Supressors on ELR supersonic shots?

[Migs]

Friends

I saw some video on an extreme long range rifle event. Some of the competitors were using suppressors. So what is the logic behind:

-using a suppressor if your bullet has to be super sonic in order to reach long distances. Supersonic means there will be lots of noise anyway since the sound barrier is being broken.
-putting a cover on a suppressor-why?

Thanks for enlightening me

Migs

 

[Art Eatman]

If you can reduce the db without reducing accuracy, what's not to like?

 

[9x19]

The covers are used to break up the heat waves coming off the silencer, so there is no heat mirage to sight through.

 

[Migs]

Thank you all very much. I had no idea. I thought a suppressor only worked with subsonic rounds. And the mirage makes sense.

 

[T. O'Heir]

"...no heat mirage..." The mirage you need to deal with is the one down range, not off the barrel or muzzle. Whether there is mirage, this time of year, depends on where you are. Up here, at this time of year, you're far more likely to be dealing with rain, snow, sleet or all three in a single day.
Lotta times people will do stuff like that just because they legally can rather than having a need. Logic rarely has anything to do with it.
"...only worked with subsonic rounds..." They do. The sonic boom you hear from a gun shot is the air slamming back after the bullet has passed or the muzzle gases have dissipated.

 

[Rimfire5]

I've shot both .308 and 6.5mm Creedmoor rifles with supersonic loads (about 2,650 fps muzzle velocity) with and without a .30 cal. suppressor measuring velocity with an Oehler chronograph.

I didn't notice any change in accuracy at 100 yards with either rifle between using the suppressor and shooting without it.

Even with the supersonic loads, the suppressor made enough difference in reducing the sound behind the rifle that I think we could have removed our hearing protection. I can't attest to how much it attenuated the sound in front of the rifle, however.

But the .308 gained about 30 fps in muzzle velocity and the 6.5mm CM gained from 16 to 18 fps using the suppressor that added 8.5 inches beyond the muzzle.

I would think that the difference in gain of muzzle velocity between a .264 bullet in a .30 cal. bullet was due to the bullet fit in the suppressor tube. The added space between the suppressor tube and the .264 bullet might have caused some loss of back pressure in the added 8.5 inches of the suppressor even though the suppressor would allow some leakage even with a .30 caliber bullet.

 

[Migs]

Very interesting. I'm learning this PRS or ELR sport and it is an ocean of information. (Not to mention the reloading aspect)

 

[Brian Pfleuger]

"...only worked with subsonic rounds..." They do. The sonic boom you hear from a gun shot is the air slamming back after the bullet has passed or the muzzle gases have dissipated.

That's not true at all. Suppressors work quite well on super-sonic rounds. By far, the majority of sound from a gun comes from the rapid expansion of gases which come out the barrel after the bullet exits.
The shock wave from the bullet itself accounts for a small fraction... roughly the equivalent of a normal .22 rifle by most accounts.... which makes sense, since a .22 rifle is typically super-sonic but the muzzle pressure is very low compared to high-powered rifle rounds.

And the sound of anything super-sonic has nothing to do with air "slamming back"... no more than thunder is the air "slamming back" after lightning. A "sonic boom", whether from lightning, bullets, aircraft or anything else is caused by sound waves being compressed because their source is moving faster than they can propagate away.

 

[JohnKSa]

I thought a suppressor only worked with subsonic rounds.

Suppressors only reduce the sound of muzzle blast. They do not reduce the supersonic crack, but that's only part of the overall noise of discharge.

The overall noise of the discharge will be reduced because the muzzle blast is reduced--but you are correct that the supersonic crack will remain.

"...no heat mirage..." The mirage you need to deal with is the one down range, not off the barrel or muzzle.

Heat mirage off the barrel during a long string of fire can definitely cause issues with seeing a clear image through the scope. The mirage downrange can also be a separate issue, but that doesn't mean that heat shimmer from the barrel is not.

"...only worked with subsonic rounds..." They do. The sonic boom you hear from a gun shot is the air slamming back after the bullet has passed or the muzzle gases have dissipated.

The sonic boom is the shockwave from the bullet passing through the air at supersonic velocities.

 

[Mobuck]

Some bullets produce more air disturbance than others BTW.

 

[Jim Watson]

Back before NRA disallowed silencers in F class, there were a couple of guys in the area with suppressors on .308s.
Accuracy was as good as a bare barrel. Recoil was less, a silencer is a pretty good compensator; I think the main reason they were banned.

Report was muffled, but it was NOT hearing safe even if they were the only ones shooting. If you did put up with it for a shot or two, you could hear a whistle after the shot as the can bled pressure down.

Supersonic Crack! as the bullet passed over the target pit was the same as a bare barrel, loud enough that I wore plugs all the time.

 

[TXAZ]

Some bullets produce more air disturbance than others BTW.

I have a Barrett .50 cal with a suppressor.
From the shooter's perspective, it's much quieter with the suppressor than not.

From an observer's perspective it's still louder than any other weapon on the line.

From someone's perspective in the target pit area, the supersonic screech doesn't change one bit.

(What does significantly change is the POI with the 5+ lb suppressor)

 

[MarkCO]

Brian and John in posts #8 and #9 are correct.

Realize that all suppressors are not equal however. I have several, and one that is movie quiet round 1, but unless you wait 2 or 3 seconds, gets louder. My integrally suppressed .308 is so quiet you really do not need hearing protection if you are at the shooter position or further back. Right off to the side, yes, you need it due to the supersonic crack.

The suppressor I use for PRS type matches reduces recoil a little less than a middle of the road comp, and shrinks my groups about 10 to 15 percent. I pick up about 10 to 15 fps and my POI changes a little due to that out far. That is on a .950 Bull barrel. On the smaller tapers, the POI will drop a little. Suppressor cover mandatory for multiple shots in most cases.

 

[FrankenMauser]

Suppressors can be very effective at reducing muzzle report, as well as reducing recoil.
The real "fun" is with subsonic loads; but suppressing supersonic stuff is still well worth it.

I've been running my .270 Win with a SilencerCo Harvester 300 this year. Without hearing protection, the report from full power (supersonic) loads is a crack like .22 Mag or a light .22 Hornet out of a rifle, followed by a 'hiss' from the suppressor.
Recoil seems to be reduced even more with that suppressor than what other shooters describe with theirs, likely because the Harvestor has an integrated muzzle brake. Recoil is a highly subjective matter, perceived differently by different people, but, to me, full power loads through that .270 with the Harvester feel even 'softer' and 'smoother' than .223 Rem out of an AR-15. It's nothing.

While nothing like movie magic, reducing the report from a very loud 'bang' to a minor 'crack' and 'hiss' is a substantial change.
And, under certain circumstances, 'silencing' supersonic loads can be more beneficial that doing so with subsonics.

For starters, you still get the trajectory of a supersonic load.
On top of that, you reduce shooter fatigue at competitions.
For hunting, you save your hearing. ...And potentially more.

I dropped two antelope this year, one after the other, with the aforementioned rifle and supersonic ammo, with the animals at 300-350 yards. To myself and a hunter next to me, the impact sounded louder than the rifle's report. The animals didn't seem to hear anything but the impact. Each time, the herd jumped, looked at my victim on the ground with confusion, and went back to feeding. A hunter about 300-400 yards away never heard the rifle. He heard the impact on one of the speed goats, but not the rifle. Another hunter, about 500 yards away, never heard anything. He heard an unsuppressed rifle banging away about 1/4 mile away, but neither shot from mine.

To non-hunters, that may seem like the 'good' I'm attempting to highlight is being able to remain undetected for poaching or other nefarious activities. But the beauty of it, for us, was that it kept the herds from spooking and running into the next valley. So, we were able to pick some more off later and fill eight tags in a small area, in one day.


For that rifle, in particular, accuracy has improved with a few loads, versus shooting them from a naked barrel.
But, as noted by other members, point of impact does shift if the suppressor is removed. The rifle's zero must constantly be re-verified, or even adjusted, if the suppressor is removed or installed.
**Both of the above are, in my opinion, more a function of barrel harmonics than anything happening internally with the suppressor. But I do not discount the possibility of changed gas flow being a factor.