Armory Sponsor
Posted: 9/11/2012 5:29:17 AM EDT
|
Help me clarify something to myself.
Am I correct in saying that POI shift with a suppressor vs. without a suppressor is an artifact of both barrel stiffness and the suppressor in question? I hear a lot of companies talk about their suppressors having "minimal" POI shift, but I've always wondered if that is assuming an HBAR contour, and that the results might be quite different with a LW contour of the same length. Thanks. |
|
Yes, The change in POI is mostly due to bbl flex from having stress applied in a side to side or up down direction. Examples are from a barrel being pushed sideways from a warped or ill fitting stock, up pressure from a non free floated bbl or down ward pressure from a weight attached to the end. All barrels will flex if enough stress is applied. So, both weight of the suppressor and thinness of the bbl combine to result in different POIs.
The suppressor can also affect bbl harmonics, resulting in a change in accuracy too. MLG |
|
Lighter barrel contours can be affected by a suppressor's weight if it gets hot enough.
The biggest contributing factors to zero shift are thread concentricity and the type of baffles in the suppressor. And mostly concentricity to the bore... When a suppressor MFG makes a direct thread can, your accuracy will likely be better than with a QD mount. There's fewer links in the chain to throw off propellant gases that will inevitably push the bullet in a different direction if threads and mounts and freebores don't line up perfectly. AAC designed some cans with different baffles to enhance accuracy while others are designed around maximum suppression. A pencil contour with perfect threads will have less shift than a HBAR with threads that are 4 thousandths out. Posted Via AR15.Com Mobile |
|
Thanks for the replies.
I have a 16" HBAR whose threads were checked for concentricity, and the barrel is free floated. I've got an OPS Inc brake and collar on it and am saving up for the can. Judging from your answers, it should have minimal POI shift and be a great host! 
The rifle in question: 
|
|
Quoted:
Nice rifle. FWIW, according to ADCO, Ops Inc is the only company which checks it's mounts concentricity. I think minimal POI shift, and lower report are in your future
Posted Via AR15.Com Mobile Haha thank you and very good to hear. It really seems like a shame that Ops Inc doesn't get more love on here. Everything I've read about them is all about how good their cans are, how durable they are, and how Ron will bend over backward to make sure you get a good product; I'm not even surprised to hear that they check the concentricity of the mount. I wish more people bought their products, but I imagine having to have a certain profile barrel to accept the collar is part of it. |
|
My own experience with a pencil and some other barrels has shown in my case at least that the barrel profile has nothing to do with POI shift. Atleast not a sagging effect. When hot, my groups open up a little. but in slightly bigger circle not off to one direction as if the barrel is bending. This happens on several guns with the same suppressor. A YHM Phantom in 5.56,
|
|
Quoted:
Quoted:
Nice rifle. FWIW, according to ADCO, Ops Inc is the only company which checks it's mounts concentricity. I think minimal POI shift, and lower report are in your future
Posted Via AR15.Com Mobile Haha thank you and very good to hear. It really seems like a shame that Ops Inc doesn't get more love on here. Everything I've read about them is all about how good their cans are, how durable they are, and how Ron will bend over backward to make sure you get a good product; I'm not even surprised to hear that they check the concentricity of the mount. I wish more people bought their products, but I imagine having to have a certain profile barrel to accept the collar is part of it. Ops Inc and Allen Engineering have a different tone than anything else on the market. Allen Engineering is the side company Ron also runs for R&D as well as some of his own products, which are similar to the Ops products except they do not utilize a brake for attachment (still over the barrel but muzzle is a direct thread mount inside the can). I really don't understand why some people are turned off by having a barrel contoured for an Ops/AE suppressor but have no problem doing the same for a SureFire, certain AAC or other products with over the barrel designs. The Ops/Allen Engineering mounting solution is a rock solid one. I run an Ops 16th Model on a select-fire M4 and AR SBR and the suppressor never loosens up. I run an AE30 on my precision bolt-action .308 and it is the quietest .30-cal suppressor I've ever heard even on 300Win Mags. 
Some of my Ops Inc products... 
I own and enjoy a lot of different suppressors. The Ops/AE remain my favorite rifle suppressors. Now, regarding the original post/question... I agree baffle design and weight are big contributing factors. With the weight it is really more of a harmonics issue on medium and heavier contour barrels. My AE suppressor isn't the lightest weight solution on the market but I get minimal POI shift. I've shot lighter weight suppressors including Titanium ones on the same rifle and have gotten worse shift. When buying a suppressor for your rifle just go into it assuming you'll have some shift. As long as it is repeatable it (to me) really isn't that big of a deal. Mark |
Armory Sponsor