Barrel lenght vs. fps suppressed

[Mikey]

We are talking big bore here.
Specifically, Airforce Texan 45 caliber
I know that the longer the barrel, the faster the slug, to an extent.
I have read on the  forums that you will loose approximately 20 fps per 1" of barrel length lost.
My question is what happens when you add a suppressor?
In theory,  the air pushing the pellet is loosing
energy by expanding at every baffel and expansion chamber but, it IS STILL PUSHING!
So... if you cut 5" off the barrel and added a 8" can, would the fps go down, up or sideways?
I suppose that could be answered by just shooting your gun with and without the moderator and looking at the data.
Does anybody have actual crony data with and without a moderator on their gun?
What do you think?

[jackssmirkingrevenge]

Back when I had a Daystate MK3 I had measured two 5 shot strings, both starting from the same fill pressure.  The second one was with the Daystate "Airstream" moderator fitted:

860, 860, 870, 869, 872 (866.2 average)

877, 880, 884, 882, 883 (881.2 average)

The moderator did boost the velocity, but only by 15 fps, nowhere near what the equivalent barrel length would have given.

[Mikey]

That's interesting.
Maybe when the weather breaks I'll try that with my Vulcan .25

[ShakySarge]

I have noticed a slight increase in FPS when using the suppressor. Not much, as stated above, no more than 10-20FPS but an increase nonetheless. I do not think that reducing the barrel length and adding the suppressor would be enough of a gain to make it worth while. As stated, every inch you remove, would have to be compensated for. The smaller the diameter of the suppressor, the more speed it will produce in my findings, but, you would likely end up with a longer overall length once the suppressor is in place. So, no real advantage there.

Perhaps a shorter, fatter suppressor would be in order that would maintain the original length of the barrel.

Just my 5 cents though.

[Mikey]

Yeah, I am just sitting around watching the snow fall and thinking too much.
I'd like to quiet this beast a little but it is already 4 feet long!

[ShakySarge]

I absolutely get that. My Sumatra comes in at 51" with the suppressor, 4'-3" is quite long indeed.

[rsterne]

It seems normal to gain a small amount of velocity with a surpressor…. but if you are shortening a barrel to fit one, you will certainly not gain back what you lost by cutting the barrel, staying with the same length overall....

Bob

[Blacktalon6]

Airforce is saying that the SS and the carbine have the same power and they both have the same barrel length.

[Mikey]

Thanks for all the input to my seemingly dumb thoughts!
I think that I will get Tony's gen 6 and just live with the extra 8 inches.
Heck, at 56", it will make a good crutch if I fall in the woods and break a hip!
Does anyone make a wheel kit for the bypod?
Could push the beast like a wheelbarrow!
Just kidding.

[Hayfoot]

But I've also heard that adding a suppressor decreases the turbulent out flow of air from the barrel, as well... resulting in increased accuracy.
So ~ for what you are losing in decreased barrel length, it could be mitigated by other benefits.

[Mikey]

I have several licensed suppressors for my powder burners and can attest to the fact that it does help accuracy. For me, I think it's probably from reducing the recoil.
My state has just this year allowed air rifles for big game hunting.
I hate to start cutting down the barrel and losing feet per second because that equates to loss of energy on the target.
Not to mention the game being able to see that slow-moving slug coming at of them and jumping out of the way!

[rkr]

I have several licensed suppressors for my powder burners and can attest to the fact that it does help accuracy. For me, I think it's probably from reducing the recoil.
My state has just this year allowed air rifles for big game hunting.
I hate to start cutting down the barrel and losing feet per second because that equates to loss of energy on the target.
Not to mention the game being able to see that slow-moving slug coming at of them and jumping out of the way!

There was some experimentation in UK using 12 fpe .30 for ratting. A conclusion was that at around 300 fps mark rats were able to dodge the bullet. At 500 fps (.25 at 12 fpe) they had not enough time to react.

[Hayfoot]

There was some experimentation in UK using 12 fpe .30 for ratting. A conclusion was that at around 300 fps mark rats were able to dodge the bullet. At 500 fps (.25 at 12 fpe) they had not enough time to react.

That's something I enjoy about this hobby/sport... that there is quite a bit of science behind the results of our participation! Sure for some it's 'point and shoot'... but you can also pour yourself into the mechanics to any degree you like and be rewarded by enhanced benefits!    :-)

[subscriber]

There was some experimentation in UK using 12 fpe .30 for ratting. A conclusion was that at around 300 fps mark rats were able to dodge the bullet. At 500 fps (.25 at 12 fpe) they had not enough time to react.

Here is a video of the 12 ft.lb .30 pellet dodging rat: 


I think the rat is reacting to the sound...

[jackssmirkingrevenge]

I think the rat is reacting to the sound...

That would be my estimation too, I mean the pellet is "slow" but 300 feet per second means that it will take 0.2 seconds to cover 60 feet, that does not seem like enough time for the rat to look up, notice the pellet and dodge it Neo style.  The muzzle noise on the other hand will reach it about 0.05 seconds, enough for the reflex to scurry off to kick in before the pellet arrives.