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Old August 27, 2019, 03:14 PM   #1
MTT TL
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How Much POI Change?

Several Questions for those that swap cans and guns around.

On average how much POI change do you see when attaching a suppressor as opposed to without?

Does this seem to vary much based on using a heavier can on a weaker caliber gun (say a can rated for .308 on a 300BO or .223 on a 22lr)?

How much does ammo type, velocity and grain size effect the change?

For those that use adapters is the change reduced using an adapter as opposed to a screw on type?

Looking for comparisons with my experiences.
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Old August 28, 2019, 11:23 AM   #2
TrueBlue711
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I asked this same question about a year ago and the best answer I got was "test it for yourself and get your own data". I have a SilencerCo Omega 300 can that I swap around on 2x 5.56 AR style rifles, 1x 300 Blackout and a SCAR 17. And since I swap it around, I don't do direct thread on. I haven't tested the POI shift on my 5.56s or the SCAR, but I have shot my 300 Blackout a LOT suppressed and unsuppressed. Since the purpose for my 300 BO is for close range shooting, it's sighted in at 50 yards with a red dot and I haven't pushed it past 100 yards. So I can't attest to any POI shift past 100 yards. But I haven't noticed any POI shift when I take the can on and off (using the same ammo) shooting it at 50 yards. I do see a POI shift when I use different ammo (namely subsonic vs supersonic), but that goes without saying.

I also have a .22 suppressor that I swap around between my 10/22, Ruger Mark III and my .22LR AR upper. Again, no direct thread. As with the 300 BO, I haven't seen any POI shift going between can and no-can.
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Old August 28, 2019, 12:03 PM   #3
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I have been testing it myself and getting my own data. I was just curious what others have found.
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Old August 28, 2019, 07:01 PM   #4
Bart B.
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Adding weight to the muzzle lowers the frequency it vibrates at vertically. Bullets will depart at a different angle to the line of sight.

Groups with the weight on are usually higher if bullets leave on the muzzle up swing, lower if on the down swing. If bullets leave about the extremes of the muzzle swing, the reverse can happen or not be significantly different.

Last edited by Bart B.; August 28, 2019 at 07:29 PM.
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Old August 28, 2019, 10:42 PM   #5
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At an extreme, a Barrett .50 BMG M107A1, on target at 1000 yards clean, will see a POI massive difference with the QDL suppressor. The QDL weighs 5 lbs, cantilevered on the 29” barrel ends up hitting around 80” low, hitting around 800 yards instead of 1,000. MV is pretty close but there is a major POI change.
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Old August 29, 2019, 07:51 AM   #6
zeke
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If memory holds, most the riflles am using cans on see from .3 to .6 mil shift down at 100 yds. Believe the 300 BO and 308 show more with sub sonic loads, but would have to check the records. The 22 lr has a noticeable shift down at 50 yds.
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Old August 29, 2019, 08:44 AM   #7
MTT TL
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I will say I have never seen one shift up even though there tends to be a marginal velocity increase. Part of the reason I am wondering is because recently I ran a smaller (but adequately rated) can on an AR-10 with supersonic loads. There was huge shift to the left on the order of 14" at 25 yards. I found this very odd. Once I dialed it in, it was very consistent even after the can was very hot.

When I swap .22lr cans out on different weapons I find that there is merely a minor shift downward. I tend to lose consistency after 100 rounds or so, when the can has heated up a lot. This is much worse if I run HV ammo, which I tend to avoid.
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Old August 29, 2019, 09:08 AM   #8
zeke
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14 inches left at 25 yards is way, way, way beyond the norm. Enough to be concerned on mounting/baffle strikes. Am getting slight shift to left, again would have to look it up.

Some of mine use brand specific muzzle brakes/ flash hiders. Some screw on directly.

Some rifles do not have a squared shoulder behind threading, and can fails a centering test.

Am using steel rods made to check centering of bore to can baffles.

A more specific description of the can, mount and rifle may help.

Last edited by zeke; August 29, 2019 at 07:24 PM.
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Old August 29, 2019, 09:31 AM   #9
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I fired over 50 rounds with no baffle strikes or any other odd behavior. But I was pretty shocked by the movement.

The suppressor came with a nut to provide a square shoulder to rest on and to provide a friction lock. These seem to have worked just fine.
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Old August 29, 2019, 07:26 PM   #10
zeke
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Can ya say what specific can and rifle? I can't explain it, but would be wary.
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Old August 29, 2019, 09:16 PM   #11
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Sure, the rifle with the huge movement is an early DPMS AP4 (pre-Freedom Group). Round count is about 1200 rounds on the original barrel. The can in question is Hardened Arms Black Widow II. Since it was rated for .308 I took it off my 300BO pistol to see how it would perform. The sound reduction was underwhelming.

The AP4 is a sub 1 MOA rifle. With the can on it, it is right around 1 MOA, which is not bad IMO. I'd ask Hardened about it but they are in Chapter 15.
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Old August 31, 2019, 05:47 AM   #12
zeke
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The only thing can find on this can is it is mono-core, serviceable and designed to be pin welded. Guessing you already dissembled to check for bore strikes/looseness, that appears to just leave the mounting system.

That is almost 5 feet at 100 yards.
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