View Full Version : Suppressor(s): Existing atmosphere can change accuracy in a rifle?
islandermyk
03-08-2013, 22:06
So I took out the GAP and the new SDN6 can.
http://i418.photobucket.com/albums/pp261/brutaltlr/The%20Guns%20and%20shoots%20and%20%20all%20related %20to%20it/IMAG1488_zps18e70125.jpg
Did a 5 shot group cold bore without the can. It was fine and dandy. (Top left)
Okay.. now with the SDN6 on. (Top right) First shot dang near dead on. Second shot was right below it. Third one another inch below it. I was shooting pretty fast strings, but when I saw where that third one hit I pretty much freaked out and stopped for a minute or two. So I then shot the fourth one and got it dead nuts again (right beside the first shot) and the fifth one is on the left of the second shot.
Seeing that first group shot with the can on made me wonder....
Note the middle target. That one was with the can, but this time with a different shooting strategy.
After every shot in this 5 shot group I left the bolt open for little more than 3 seconds ejecting the spent cartridge.
So do you think the existing atmosphere from residual pressure in the can after a shot can cause a spread in groups?
By the way, I love this SDN6... been smacking steel at 1000 yards and everything inside that. It really shines from 800 and inside of that... and the rounds were hand loaded 175 gr SMKHPBT 43.7 gr Varget[Beer]
Did you get the golfball?
I don't think you could have any "residual pressure" in the suppressor.
Where is Hoser? He might have some knowledge on the subject.
islandermyk
03-08-2013, 22:12
Did you get the golfball?
yeas I did... and I brought that home with me [ROFL1]
Got it dead smack center.
islandermyk
03-08-2013, 22:15
I don't think you could have any "residual pressure" in the suppressor.
Where is Hoser? He might have some knowledge on the subject.
I wonder cause when I was shooting faster strings smoke was coming out of the action... it got me thinking too that since the SDN6 is shorter... I don't know... It's driving me crazy trying to make sense of all this [Bang]
Just an idea, but your spread was vertical. Since you were shooting faster, could it have been breathing? I don't have any kind of shift like that with my can ( different can but ? ) Thats the same load I run in my .308 43.7gr of Varget! Works great.
I wonder cause when I was shooting faster strings smoke was coming out of the action... it got me thinking too that since the SDN6 is shorter... I don't know... It's driving me crazy trying to make sense of all this [Bang]
Lend me your can and I will figure it out for you. :D
islandermyk
03-08-2013, 22:53
Just an idea, but your spread was vertical. Since you were shooting faster, could it have been breathing? I don't have any kind of shift like that with my can ( different can but ? ) Thats the same load I run in my .308 43.7gr of Varget! Works great.
You could be right.. I wasn't watching my breathing on that one.
I was shooting prone....
It was that one time I pulled the bolt back and watched the case eject that caught my attention. The case almost acted like a plunger sucking the left over smoke out of the barrel this question...
Who knows.. it's my first can.. I'm pretty sure I'll have more weird questions coming along the more I shoot with them[Dunno]
You may need to swab it.
http://youtu.be/LoSLZP0e-M4
Haven't seen a shift like that in either of my TBAC cans . My first guess would be a lack of preload on the bipod since it went away when you started concentrating again . That being said AAC has had a lot of issues with their QD mounts and if your can uses one that can cause issues also .
islandermyk
03-09-2013, 07:13
You may need to swab it.
[LOL]
Haven't seen a shift like that in either of my TBAC cans . My first guess would be a lack of preload on the bipod since it went away when you started concentrating again . That being said AAC has had a lot of issues with their QD mounts and if your can uses one that can cause issues also .
The Brakeout I have on the rifle locks up pretty tight with the can. I think it maybe my shooting at the time getting spoiled that there was barely any recoil with the can on.... whoa! whoa! whoa...! lets not talk about my shooting [ROFL1]
Will there be residual pressure in a can (shooting in fast strings), and will or can that effect accuracy?
There is no residual pressure. The combustion gases will result in slightly higher density in the bore and can for several seconds. However, from a thermodynamic perspective, the difference is statistically insignificant.
islandermyk
03-09-2013, 08:16
There is no residual pressure. The combustion gases will result in slightly higher density in the bore and can for several seconds. However, from a thermodynamic perspective, the difference is statistically insignificant.
God I wish there was a way to see through a can to watch how gases flow, compress, etc.. through the baffles in a can... especially between a short and longer suppressor.
I was thinking when the bullet leaves the barrel on its way toward the can... pressure is being built up in front of the round and when it enters the suppressor... pressure (I would think) is building up with existing higher density gases and would that actually affect the flight path of the round.....?
You're over thinking it. Concentrate on your technique, be consistent.
God I wish there was a way to see through a can to watch how gases flow, compress, etc.. through the baffles in a can... especially between a short and longer suppressor.
I was thinking when the bullet leaves the barrel on its way toward the can... pressure is being built up in front of the round and when it enters the suppressor... pressure (I would think) is building up with existing higher density gases and would that actually affect the flight path of the round.....?
There is. I do this in CFD packages. When a round is fired, the column of gases in the barrel are part of the ejecta. When a HV round leaves the barrel, it is flying supersonically backwards. That is why the base of the bullet affects accuracy (specifically nutation). The suppressor strips the gases off in a more controlled manner, and sooner, thus increasing accuracy (with a good can). BUT...
You're over thinking it. Concentrate on your technique, be consistent.
This is better advice.
islandermyk
03-09-2013, 08:52
You're over thinking it. Concentrate on your technique, be consistent.
[ROFL1]
I probably am... but just think!
The next can you might want to get...
Would the shorter or longer can be more accurate?
Would more baffles or less would be more accurate?
islandermyk
03-09-2013, 08:54
This is better advice.
[ROFL1] enough about my shooting [LOL]
To ellaborate on MarkCO's point (NERD ALERT!).
Yes there will be a bit of pressure, but less than 2 bar (2x standard atmospheric pressure). Consider that a 308's max SAMMI is about 4,500 bar in the chamber. It will be somewhat lower than that by the time it gets to the can, but you are still talking thousands of time higher pressure during the shot than with residual pressure.
If anything, the heating of the barrel would be the first place to have a significant reaction. Between heating, and swelling and a slight change in its metallurgic stiffness (K = M/phi) wherein metal becomes more maliable as it heats up, you would see changes several fold more significant than pressure changes. I'm still not sure its enough to cause these big differences, but it may be measurable as some fraction of an MOA on a target. Changing the Length and end weight on a barrel (with a can) could conceivably produce more change due to heating:
Lets consider a more direct approach at determining the stiffness of the barrel,
K = nAE/L. N is a constant for a given material, considering the boundary conditions and A is a constant considering the cross sectional area of the material, and E is a constant considering the elasticity of the material (all constant for this problem as we aren't swapping the material). As we don't want a value but merely a rough picture of the system, lets assume n=1 and A=1 and E=1 for this material, and throw them out, so we have (K=1*1*1)/L, therfore K (stiffness) = 1/L (length. So we see as Length goes up, our stiffness goes down. This proves there will be some change in POI due to a change in stiffness by adding length to the system.
Yes there is a flaw in this logic, as n,A,E are different between the supressor and the barrel. But we could come up with some approximation for the suppressor as a smaller increase in the length of the barrel that will behave the same. So we still know L is going up. Therefore, stiffness goes down.
Lets also consider that the amount of deflection is related to the moment of inertia vs the moment of force applied to the barrel. Again we have K=M/phi. Lets rewrite that as phi = M/K, where phi is the amount of barrel deflection, M is the moment of force applied, and K is the stiffness. We know that K has gone down, which means a bigger phi, deflection. But we have not yet considered M. M is the summation of all moments of force throughout the system, an integration from start to end for those with some calculus background. Lets consider than the barrel will have the same forces applied to it with can on, or can off. This can be ignored. We can therefore account (to a second order approximation) for only the moment of force applied to the can. While smaller than that applied to the barrel, because only pressure puts force on the can rather than the projectile itself, this smaller force will be enhanced by its radial distance from our pivot point (considering the barrel as a pivot around the action, as it moves more closely to a radial system than a linear system). And some copy/paste from my formula editor http://upload.wikimedia.org/math/7/1/a/71a004837db898a8379cb2c7f1b017d0.png is the radial equation for moment of inertia in a radial system. As we can see, the moment of inertia increases exponentially with increased radius. Because radius is squared, we get large gains as we increase the radius upon which the force is applied. So even the smaller forces there play a role due to increased radius. So now we have phi = M/K, where K is getting smaller, and M is getting bigger both as heat increases, so we may see some noticeable observations depending on how much each change. Running rough numbers, I come up with something at least measurable, but even my most overly liberal estimations put it just over 1MOA.
Conclusion: You get better accuracy when you go slow, because everyone gets better accuracy when they go slow and take their time on a shot.
If you've made it this far, thanks for nerding out with me for at least a few minutes.
I blame the trigger presser.
Load the bi-pod harder and focus on your rear bag.
Best advice is to get a really accurate 22 and shoot it a lot at 50-100 yards. One little itty bitty flaw in what you are doing will move the bullet quite a ways compared to a centerfire.
islandermyk
03-09-2013, 11:45
To ellaborate on MarkCO's point (NERD ALERT!).
Yes there will be a bit of pressure, but less than 2 bar (2x standard atmospheric pressure). Consider that a 308's max SAMMI is about 4,500 bar in the chamber. It will be somewhat lower than that by the time it gets to the can, but you are still talking thousands of time higher pressure during the shot than with residual pressure.
If anything, the heating of the barrel would be the first place to have a significant reaction. Between heating, and swelling and a slight change in its metallurgic stiffness (K = M/phi) wherein metal becomes more maliable as it heats up, you would see changes several fold more significant than pressure changes. I'm still not sure its enough to cause these big differences, but it may be measurable as some fraction of an MOA on a target. Changing the Length and end weight on a barrel (with a can) could conceivably produce more change due to heating:
Lets consider a more direct approach at determining the stiffness of the barrel,
K = nAE/L. N is a constant for a given material, considering the boundary conditions and A is a constant considering the cross sectional area of the material, and E is a constant considering the elasticity of the material (all constant for this problem as we aren't swapping the material). As we don't want a value but merely a rough picture of the system, lets assume n=1 and A=1 and E=1 for this material, and throw them out, so we have (K=1*1*1)/L, therfore K (stiffness) = 1/L (length. So we see as Length goes up, our stiffness goes down. This proves there will be some change in POI due to a change in stiffness by adding length to the system.
Yes there is a flaw in this logic, as n,A,E are different between the supressor and the barrel. But we could come up with some approximation for the suppressor as a smaller increase in the length of the barrel that will behave the same. So we still know L is going up. Therefore, stiffness goes down.
Lets also consider that the amount of deflection is related to the moment of inertia vs the moment of force applied to the barrel. Again we have K=M/phi. Lets rewrite that as phi = M/K, where phi is the amount of barrel deflection, M is the moment of force applied, and K is the stiffness. We know that K has gone down, which means a bigger phi, deflection. But we have not yet considered M. M is the summation of all moments of force throughout the system, an integration from start to end for those with some calculus background. Lets consider than the barrel will have the same forces applied to it with can on, or can off. This can be ignored. We can therefore account (to a second order approximation) for only the moment of force applied to the can. While smaller than that applied to the barrel, because only pressure puts force on the can rather than the projectile itself, this smaller force will be enhanced by its radial distance from our pivot point (considering the barrel as a pivot around the action, as it moves more closely to a radial system than a linear system). And some copy/paste from my formula editor http://upload.wikimedia.org/math/7/1/a/71a004837db898a8379cb2c7f1b017d0.png is the radial equation for moment of inertia in a radial system. As we can see, the moment of inertia increases exponentially with increased radius. Because radius is squared, we get large gains as we increase the radius upon which the force is applied. So even the smaller forces there play a role due to increased radius. So now we have phi = M/K, where K is getting smaller, and M is getting bigger both as heat increases, so we may see some noticeable observations depending on how much each change. Running rough numbers, I come up with something at least measurable, but even my most overly liberal estimations put it just over 1MOA.
Conclusion: You get better accuracy when you go slow, because everyone gets better accuracy when they go slow and take their time on a shot.
If you've made it this far, thanks for nerding out with me for at least a few minutes.
you got to be sh*tting me [Shock]
I think I understand.... it does have some effect, and I have to learn how to slow down and shoot better.
Yep, I'm over thinking this ain't I? Just want to get a general idea of what would be a good suppressor design to go with on my next buy.... There's seems to be a sacrifice for everything here. If I go short.. I'll get the accuracy but not the quietness. If I go longer I'm sacrificing accuracy for quietness.. is this right?
Damn, you guys thinking like this early in the morning... sh*t... making my head hurt [Beer]
islandermyk
03-09-2013, 11:57
I blame the trigger presser.
Load the bi-pod harder and focus on your rear bag.
Best advice is to get a really accurate 22 and shoot it a lot at 50-100 yards. One little itty bitty flaw in what you are doing will move the bullet quite a ways compared to a centerfire.
Believe me... I know that there was an extreme lack of focus in my shooting that day. Was to excited with the new can and all [Tooth]
For some reason I was paying more attention to other things like the felt recoil, how much back pressure I was getting from shooting the Krink suppressed and .45's (with the Ti-rant) which got me started with this.
All I can say is.... You guys are awesome! [Beer]
Any movement between the can and the muzzle adapter is going to be bad for accuracy . The problems with AAC's mounts goes way back , that's why they keep adding teeth to the ratchet surface but the issue is in the tapered seat dimensions . QD cans will never be my first choice in a precision rifle can .
But back to the part where the rifles group tightened back up when the fundamentals were followed really is an indication of shooter error . The biggest causes of vertical dispersion are bipod preload , rear bag technique , and cheek weld issues .
I shoot all 3 of my precision rifles exclusively suppressed , 260 , 308 , and 338 with a 30P and 338BA . None of them will throw shots out of the group regardless of how fast I shoot them . One of the best groups I've fired out of my 260 was 5 rounds in about 30 seconds while sharing a chrono and was more interested in the numbers than group size , put all 5 into just over 1/2 inch at 200 .
The reduction of recoil and the way the recoil impulse is changed with the suppressor on can and will lead to sloppiness in the fundamentals because the rifle is more forgiving to shoot but they are just as important .
There is no reason to sacrifice accuracy for the noise reduction .
islandermyk
03-09-2013, 15:27
Any movement between the can and the muzzle adapter is going to be bad for accuracy . The problems with AAC's mounts goes way back , that's why they keep adding teeth to the ratchet surface but the issue is in the tapered seat dimensions . QD cans will never be my first choice in a precision rifle can .
But back to the part where the rifles group tightened back up when the fundamentals were followed really is an indication of shooter error . The biggest causes of vertical dispersion are bipod preload , rear bag technique , and cheek weld issues .
I shoot all 3 of my precision rifles exclusively suppressed , 260 , 308 , and 338 with a 30P and 338BA . None of them will throw shots out of the group regardless of how fast I shoot them . One of the best groups I've fired out of my 260 was 5 rounds in about 30 seconds while sharing a chrono and was more interested in the numbers than group size , put all 5 into just over 1/2 inch at 200 .
The reduction of recoil and the way the recoil impulse is changed with the suppressor on can and will lead to sloppiness in the fundamentals because the rifle is more forgiving to shoot but they are just as important .
There is no reason to sacrifice accuracy for the noise reduction .
I believe it... the time I started shooting with the brake on.. I got spoiled... and having the can on... the spoiled just got rotten [Coffee] I kid! I kid! It is always a learning process every time I go out.
There is no reason to sacrifice accuracy for the noise reduction .
Now imagine if there were a way to get the best of both worlds [Flower]
There is , call TBAC
I think you will find a lot of people who have analyzed suppressors from the firing position and from an engineering perspective prefer Thunderbeast. It is not coincidence.
islandermyk
03-09-2013, 16:42
There is , call TBAC
I think you will find a lot of people who have analyzed suppressors from the firing position and from an engineering perspective prefer Thunderbeast. It is not coincidence.
I shall look into this for the next rifle... Thanks fellas [Beer]
ssgenuine
04-05-2013, 10:01
Hey Mike, did you ever figure out what the issue was? It would be cool to get together for a shoot and see how the diff cans compare. I got the SAS Arbiter Ti and the Thunderbeast 30p1. Both are thread on. As far as the breathing goes, my son has assured me that it doesn't matter at all "There is 20 rounds in the mag for a reason". I suppose there is some logic to it since if one were really, really good at shooting all rounds would go through the same hole and that would just be a waste of ammo. [ROFL1]
islandermyk
04-05-2013, 10:25
Yeah.. the real problem is my shooting [facepalm]
[ROFL1]
Having J and the rest nerd out on me I figured out that my shooting needs some work... shoot slower, learn to use a rear rest bag (I've been using a mono-pod), etc.. the rifle with and without the can is a whole lot more accurate then I will ever be. With the can on the rifle it has been very consistent which proves my shooting sucks [facepalm]
[Beer]
Great-Kazoo
04-05-2013, 11:35
I think you will find a lot of people who have analyzed suppressors from the firing position and from an engineering perspective prefer Thunderbeast. It is not coincidence.
That's because Zak and Ray are super anal (in a nice way) and expect the best for not only for them, but TBA customers too. They don't have a"let's sell some cans" They have a lets see what works consistently, then make it better.
RYAN50BMG
04-05-2013, 16:20
To ellaborate on MarkCO's point (NERD ALERT!).
Yes there will be a bit of pressure, but less than 2 bar (2x standard atmospheric pressure). Consider that a 308's max SAMMI is about 4,500 bar in the chamber. It will be somewhat lower than that by the time it gets to the can, but you are still talking thousands of time higher pressure during the shot than with residual pressure.
If anything, the heating of the barrel would be the first place to have a significant reaction. Between heating, and swelling and a slight change in its metallurgic stiffness (K = M/phi) wherein metal becomes more maliable as it heats up, you would see changes several fold more significant than pressure changes. I'm still not sure its enough to cause these big differences, but it may be measurable as some fraction of an MOA on a target. Changing the Length and end weight on a barrel (with a can) could conceivably produce more change due to heating:
Lets consider a more direct approach at determining the stiffness of the barrel,
K = nAE/L. N is a constant for a given material, considering the boundary conditions and A is a constant considering the cross sectional area of the material, and E is a constant considering the elasticity of the material (all constant for this problem as we aren't swapping the material). As we don't want a value but merely a rough picture of the system, lets assume n=1 and A=1 and E=1 for this material, and throw them out, so we have (K=1*1*1)/L, therfore K (stiffness) = 1/L (length. So we see as Length goes up, our stiffness goes down. This proves there will be some change in POI due to a change in stiffness by adding length to the system.
Yes there is a flaw in this logic, as n,A,E are different between the supressor and the barrel. But we could come up with some approximation for the suppressor as a smaller increase in the length of the barrel that will behave the same. So we still know L is going up. Therefore, stiffness goes down.
Lets also consider that the amount of deflection is related to the moment of inertia vs the moment of force applied to the barrel. Again we have K=M/phi. Lets rewrite that as phi = M/K, where phi is the amount of barrel deflection, M is the moment of force applied, and K is the stiffness. We know that K has gone down, which means a bigger phi, deflection. But we have not yet considered M. M is the summation of all moments of force throughout the system, an integration from start to end for those with some calculus background. Lets consider than the barrel will have the same forces applied to it with can on, or can off. This can be ignored. We can therefore account (to a second order approximation) for only the moment of force applied to the can. While smaller than that applied to the barrel, because only pressure puts force on the can rather than the projectile itself, this smaller force will be enhanced by its radial distance from our pivot point (considering the barrel as a pivot around the action, as it moves more closely to a radial system than a linear system). And some copy/paste from my formula editor http://upload.wikimedia.org/math/7/1/a/71a004837db898a8379cb2c7f1b017d0.png is the radial equation for moment of inertia in a radial system. As we can see, the moment of inertia increases exponentially with increased radius. Because radius is squared, we get large gains as we increase the radius upon which the force is applied. So even the smaller forces there play a role due to increased radius. So now we have phi = M/K, where K is getting smaller, and M is getting bigger both as heat increases, so we may see some noticeable observations depending on how much each change. Running rough numbers, I come up with something at least measurable, but even my most overly liberal estimations put it just over 1MOA.
Conclusion: You get better accuracy when you go slow, because everyone gets better accuracy when they go slow and take their time on a shot.
If you've made it this far, thanks for nerding out with me for at least a few minutes.
Got any other questions you need answered?
Any benchrest shooters set a world record with a suppressor? [pick-me]
Any benchrest shooters set a world record with a suppressor?
Not yet...
Are suppressors even allowed in bench rest? I don't think they are.
Are suppressors even allowed in bench rest? I don't think they are.
Dont think so. And thats a lot of weight they could put in a stiffer barrel and action.
TheBelly
04-07-2013, 11:24
I blame the trigger presser.
Load the bi-pod harder and focus on your rear bag.
Best advice is to get a really accurate 22 and shoot it a lot at 50-100 yards. One little itty bitty flaw in what you are doing will move the bullet quite a ways compared to a centerfire.
Bipods and rear bags for that, too? I have a Winchester model 52 target that was gifted to me via FIL.... It was waiting on me when I got here to tx. That's pretty creepy.
Powered by vBulletin® Version 4.2.3 Copyright © 2025 vBulletin Solutions, Inc. All rights reserved.