Does A Can or Suppresor Increase Back Pressure and Decrease Velocity??? Well????

[QuietTexan]

To be completely honest I don't think the 10x2 shots I took amounts to anything other than the "match grade" factory ammo I was using was trash. SD 32 on 10 shots is embarrassing. ES pegged on the fourth shot of twenty to 96 FPS; the entire suppressed string shot fell inside the ES of the unsuppressed string. My data might really be a case of statistics finding trends in random noise.

That's all I've got though because I've never run a string of that many rounds suppressed/unsuppressed back to back again.

 

[Veteran]

Yes, I believe the changes in velocity due soley to can or no can no matter in which direction will be small, on the order of 5 to 10 fps.

So, you gotta have really low ES and SD ammo to get a true measurement.

 

[Kmccord]

Is the velocity increase from adding inches to the barrel? So you have a 24 inch barrel and add a 6 or 8 inch can, making the barrel 30 or 32 inch which ends up burning all of your powder to increase it another 20 or 40 FPS?

 

[Shooter264]

Interesting read. I can agree with the short bbl statements. I've got a 6mm creed with an 18" Benchmark CF bbl that runs 2942 with a 7" Thunderbeast on it and 2966 unsuppressed with a brake. Tested well after bbl had sped up. Round count on bbl was in excess of 300. In longer bbls 22"+ I've seen up to 10fps gain but never anything more than that

 

[Veteran]

A can is overbored and there is no rifling, so its not truly a barrel extension in that light, but it may allow more time for the gas behind the bullet to propel it and add velocity depending on how much gas goes into the baffles, where that gas is routed, and the length of bbl and the burn rate curve of the powder used...... so if all these things are a certain design or a certain way it can certainly increase velocity.

 

[Veteran]

Interesting read. I can agree with the short bbl statements. I've got a 6mm creed with an 18" Benchmark CF bbl that runs 2942 with a 7" Thunderbeast on it and 2966 unsuppressed with a brake. Tested well after bbl had sped up. Round count on bbl was in excess of 300. In longer bbls 22"+ I've seen up to 10fps gain but never anything more than that
View attachment 340037
View attachment 340038

So CPGfan has shorter barrels, shooting faster powders in 6mm
and his data says a can causes velocity reduction vs. a brake on the same rifle and his gains are like 10 fps with no can if I read that right.

Still The the folks who have responded so far, the increases are still leading......Lets get more data points from short bbl. fast powder folks to see if theres any correlation or pattern.

 

[JTH]

I have a similar experience.

Same here. Slight velocity increase with the can. 6.5 CM, 6.5 SS, 7 Max and 300 WM. Barrels 22" to 24". Powders from Varget to H1000. Slight increase in velocity across the board.

 

[GoosePilot]

I gained 50 fps on my 7mm blaser rogue and 30 with my 6mm cm. 30 banish

 

[Veteran]

Wow those are big gains....well above the range I would expect.

The gains are gaining here....

 

[TexSavage]

I'll be interested to see how my 26" 300WSM does. With the muzzle break I'm getting 2810 on my Berg 215 hybrid, 2820 on my 208 hybrid and 3010 on my 185 juggernauts. M

 

[lancetkenyon]

Is the velocity increase from adding inches to the barrel? So you have a 24 inch barrel and add a 6 or 8 inch can, making the barrel 30 or 32 inch which ends up burning all of your powder to increase it another 20 or 40 FPS?

No. As the bore of the can is bigger than the bullet, so you build no pressure like a longer barrel would. 6-8" of barrel should add 120-200fps, not 10-20.

 

[Veteran]

Its not a barrel. It has no rifling.
It is routing gas away from behind the bullet. It is overbore so the bullet is no longer engraving.

If it was of this magnitude everyone would want to shoot cans just to get the extra kick.....Why would anyone fool with slower powders to milk out 50 fps more when they could just shoot a supressor?

If you have data, send it.

I have an open mind but 100s of fps seems overboard.....

 

[Veteran]

No. As the bore of the can is bigger than the bullet, so you build no pressure like a longer barrel would. 6-8" of barrel should add 120-200fps, not 10-20.

Here's more data. This source which ran some tests says that the velocity increased 20 fps from no can to shooting with a can,
and he tried to get enough rounds to make it statistically correlative with a high Rsquare value.

His conclusion was that the amount of change is statistically insignificant.

I tend to agree with him when I see the amount of ES and SD he had on his testing......He must have used some terrible quality ammo.

Ask Foghorn: Does a Silencer Affect the Velocity of the Bullet? - The Truth About Guns

I’ve had a number of people ask me the exact same thing after they learned I had recently received my first silencer. “Hey Foghorn, doesn’t a silencer slow down the bullet?” And to be honest, I had no idea. But I had a silencer, a chronograph and R loaded onto my computer and I was […]

www.thetruthaboutguns.com

 

[cohunt]

Increase here too, 7rm, 300wsm, 308, 30-06, 223, 6.8, 6.5cm. All slight @ 8-23 fps.

As far as a rifle suppressor being a "muffler" they are not like a normal auto muffler as a rifle suppressor has a straight through hole so it's more like a glass pack muffler. An auto muffler does not always cut horsepower, but it definitely changes the torque curve. It depends on the flo rate required by the motor-- I was in pro racing for 8 years and if the muffler has the flow capabilities that the motor needs then you won't loose horsepower but you will change the rpm/torque curve.