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Thread: Sound Suppression and Accuracy

  1. #1
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    Sound Suppression and Accuracy

    A friend of mine has been toying with the idea of buying and mounting a suppressor on his Bushmaster AR - he asked me if it would affect the accuracy of the rifle (it currently has a 20" free-floating barrel). Having no experience in this area, I don't know. Any opinions?

    (It would be a commercial suppressor, probably a YHM or similar)
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    It will probably affect the point of impact as hanging a big weight at the end of a barrel affects its harmonics.

    I've found that my rifle groups really tighten up with a suppressor for several reasons:

    - I don't flinch (call me a wimp) due to the reductions in recoil and muzzle blast, and

    - Decreased "barrel whip".
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    +1 to "Bubbles" post.
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    In addition, at least by some reckoning, a suppressor helps diffuse the muzzle blast around the projectile as it emerges from the muzzle, and keeps it from being upset by the same.

    Perhaps Oleg can come around and tell us about his adventures suppressing an AR-15. The gas buster charging handle might be a good investment.
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    I Can't Speak for AR-15's...

    ...but from what I have seen and heard, suppressors on larger-caliber rifles (e.g., precision .308 rifles) degrade accuracy beyond 100 yards.

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    thats not true.. good and modern suppressors will change the POI, but won't affect your groups..

    I have friends shooting long range matches with .50 calibers AND suppressors.
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    The Gasbuster charging handle helps a little but it's expensive. RTV sealant works well but has to be replaced every so often.

    Unless you're getting baffle strikes or your mount/can is not indexed on the shoulder of the barrel you certainly won't see a degradation in accuracy.

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    Unless you're getting baffle strikes or your mount/can is not indexed on the shoulder of the barrel you certainly won't see a degradation in accuracy.
    Hanging a weight on the end of the barrel WILL affect accuracy.

    The question really is was the rifle accurate enough before to even tell.

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    ...but from what I have seen and heard, suppressors on larger-caliber rifles (e.g., precision .308 rifles) degrade accuracy beyond 100 yards.
    Where have you seen and heard this? And why would the effect take place after 100 yards? Most seem to report a slight increase in accuracy.

    Hanging a weight on the end of the barrel WILL affect accuracy.
    Why? It is the same weight every time. I can see the weight variation between suppressed and unsuppressed causing a point of impact shift, but why would a constant weight change the spread of the groups?
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    The short answer? POI will change, however most people will experience a slight increase in accuracy. I got my first AR15 suppressor about 4 weeks ago and have experienced slightly tighter groups myself.


    Tell your friend to do a youtube search for AR15 Suppressor, there are a lot of videos showing AR15 suppressed with all the various different manufacturers of suppressors.

  11. #11
    Why? It is the same weight every time. I can see the weight variation between suppressed and unsuppressed causing a point of impact shift, but why would a constant weight change the spread of the groups?
    he didn't say groups, he said accuracy. the gun will print, but it won't have the same zero.

    The short answer? POI will change, however most people will experience a slight increase in accuracy. I got my first AR15 suppressor about 4 weeks ago and have experienced slightly tighter groups myself.
    I'd almost say you're shooting better, not the gun. a suppressor saps away the bullets lone source of energy by increasing the area it has to disperse, creating slightly lower pressures. same as shaving a few tenths of a grain out a load, the bullets POI moves.
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    Boy a bunch of comments and hearsay from people that don't know... Cool.
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    "I can see the weight variation between suppressed and unsuppressed causing a point of impact shift, but why would a constant weight change the spread of the groups?"

    You need to learn how barrels vibrate, and what the optimum position of the vibration nodes is.

    There is always some variation in powder weight, pressure, and velocity.
    There are a couple competing theories right now about the optimum node placement, but it is pretty well demonstrated that the position of the vibration nodes directly affect groping ability.

    The question remains, was the rifle accurate enough to start with to see the additional error?

    If you are shooting 1 inch groups and the suppressor adds 0.2 inches of error, the groups only increase to about 1.02 inches.

    If you are shooting 0.3 inch groups and you add the same error you open up to 0.36

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    "I'd almost say you're shooting better, not the gun. the bullets POI moves."

    And I'd completely agree. I'm shooting better due to less pre-recoil flinch, and more practice; both of which I owe to having a suppressor.

    As for it making a rifle inherently more accurate? If that were the case, every single long range competition rifle would be suppressed

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    a suppressor saps away the bullets lone source of energy by increasing the area it has to disperse, creating slightly lower pressures. same as shaving a few tenths of a grain out a load, the bullets POI moves.
    That makes no sense. You're not cutting down the barrel. You're adding to it.
    The powder has just as long to push on the bullet. The pressure escaping from the muzzle is now passing through baffles instead of the open atmosphere. Meanwhile, the bullet has left the barrel and is passing through the holes in the baffles.

    I see nothing mechanical to slow the bullet down.

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    Groups are the ACCURACY.. POI is not..
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    he didn't say groups, he said accuracy. the gun will print, but it won't have the same zero.
    I am well aware of the scientific meanings of accuracy and precision. In the shooting sports vernacular, people generally refer to groups as accuracy. Since a scope reticle can be made to put a group anywhere on the target, scientific "accuracy" is really not a factor. If your gun has the precision to put 5 shots in a 1 inch hole, shooters call that amount of "accuracy" a 5 shot 1" group. I apologize if their was a confusion in terms. In my experience, guns shoot slightly better groups with cans on.


    a suppressor saps away the bullets lone source of energy by increasing the area it has to disperse
    How does this happen? The bullet (god willing) never comes into contact with any part of the can. As soon as the bullet exits the barrel it has gotten all of the energy it is going to have. I don't see how baffles are taking any velocity away. Some people have actually reported a slight increase in velocity with a can (free bore boost), but I've never tested this myself and the numerical increase is usually minor.

    There are a couple competing theories right now about the optimum node placement, but it is pretty well demonstrated that the position of the vibration nodes directly affect groping ability.
    Would it be possible by this theory that groups would tighten with the addition of a suppressor?
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    ...but from what I have seen and heard, suppressors on larger-caliber rifles (e.g., precision .308 rifles) degrade accuracy beyond 100 yards.

    Ooohhh, that's interesting spwenger. Can you tell us more?
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    You Want More?

    Ooohhh, that's interesting spwenger. Can you tell us more?
    1. I used to work with someone who designed suppressors for Sionics and did field testing in Southeast Asia. He reported degradation of accuracy (as in increased group size) beyond 100 yards.

    2. I once spotted for a San Fernando [CA] PD SWAT officer who had a suppressed .308 precision rifle. He got nice, tight groups at 100 yards with subsonic loads but the groups opened up considerably at 200 yards. Even after switching to full-velocity (supersonic) loads at 200 yards, he was still shooting larger groups than he was accustomed to shooting at that range. At that point, he decided to remove the suppressor and got his group size back down.

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    "Would it be possible by this theory that groups would tighten with the addition of a suppressor?"

    Only if by blind luck the added mass puts the vibration node at exactly the correct spot.

    The BR guys have been using them on .22 rim fires and some center fires, and they are adjusted in thousandths of an inch to move the node around.

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    Boy a bunch of comments and hearsay from people that don't know... Cool.
    And on the internet of all places! But then, who are you, and how much do you know about people not knowing? Do you hearsay that these people do not know? Astonishing!

    OP,

    General knowledge dictates that a suppressor will not have much of an effect on accuracy. Odds are, you will notice far greater improvement in the concern that has caused you to get a suppressor than in the accuracy.
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    General knowledge dictates that a suppressor will not have much of an effect on accuracy.
    Adding a nice weight at the end is NOT generally going to improve things unless the position can be adjusted to alter the barrel vibrations.

    On a typical run of the mill rifle you may not be able to tell.

    On a rifle capable of BR type accuracy you would see a definite change.

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    PM me if you want some more info. But here is the quick and dirty of it.

    I have a Gemtech M4-02 that I mount it on a Remington 700 with a 20 inch barrel, the gun is bedded in a Mcmillan A2.

    I have found my groups open up when I first shoot the gun without the can, and then screw it on.

    Now without changing anything besides putting the can on, my POI moves 2.5 inches up and to the right. My groups also open up from about .5 to 1.5 inches.

    What I have done to solve this problem is reload, and work loads with the can on. I can then reduce my group size back to .5. Since harmonics are changed, the barrel shoots different.

    With a YHM Phantom mounted on a 16 inch shorty AR, (Eagle Lower, Bushy A4 Upper) I have found the same results. Groups that were 3/4 of an inch tend to open up to 1.25 inches. Changing the load seems to tighten the groups.

    I have found by putting a can on a rifle, the groups do open up, POI normally changes. BUT by doing load development, groups are reduced. Its easier just to work the loads, and then stick with shooting the rifle with the can on all the time. It saves you time and aggravation of POI shift.

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    BUT by doing load development, groups are reduced.
    You are altering the loads to make the vibration nodes be at better locations.

    You may be able to get back to the starting accuracy before the can was installed, but no real guarantee since you cannot move the weight around.

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    both sides are correct in this argument depending on suppressor design

    machined baffles and properly aligned suppressor means no loss in velocity or accuracy but does result in POI "shift"

    Suppressors using a "Wipe" or "Wipes" (rubber, vinyl, or other plyable material used to make contact with projectile) DO effect POI, Accuracy, and Velocity.

    these days, most people go with option A due to the fact that wipes wear out and the can's effectiveness diminishes over time directly porportional to the degradation of the wipes.

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