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POI change suppressed v. un-suppressed - Is this normal?

Posted: Wed May 08, 2013 2:59 pm
by Jer
Took the AR to the indoor range today to sight in the MBUS sights I put on a couple days back.
After getting it zeroed I decided to test both my ability and the difference between the point of impact suppressed and regular. The results are a bit odd.

I fired a total of 10 shots on this test - 5 Normal and 5 with the can.

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Conditions:
Distance: 25 meter indoor range
Ammo: International .223 45 grain Frangible ammo (long story)
Barrel: 1:8 16"
Sights: MBUS Flip Up
Position: Standing, shoulder fired, unsupported.
Target: 1.2" ID Bull's Eye

The normal shots are in green, and all in the center circle. I am still getting used to this Geissele SSA Trigger group which is fantastic.
It walked around the bull's eye a bit, but measuring with my micrometers from the center of each hole, I have a 1.006" group un-suppressed and all in the bull's eye.

The suppressed shots are in red. Admittedly, I pulled my last one and I knew I did. But the first four are all touching each other. But slightly high and right of my aimpoint. They are in a 0.56" group - discounting the pulled shot. Not really sure how to measure that.

I'm assuming that the added barrel weight on with the weapon from the suppressor helped me to stabilize my aim and tightened my group. Maybe...I don't know. Is this a typical difference between suppressed and non-suppressed shooting? Am I to expect this constant "high & right"?

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 3:19 pm
by Wahnsinn
Looks normal to me. As for the high and right, just keep running tests to make sure it's consistently hitting there. If possible, change the orientation of the can (make a mark, go by the lettering on it, whatever) to see if that has any effect. If so, make sure you orient it the same each time :D

Fun stuff huh.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 3:28 pm
by Bendersquint
Yup thats normal, especially for standing unsupported.

Try from a bench and you will see what the actual POI shift is for it.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 3:32 pm
by Jer
Good to know, folks - and thanks.

I am, overall, VERY happy with this build and really enjoying this can.
My bank, on the other hand, will feel significantly less full with this new hobby.

When I can, I'l do some bench rest shooting and get this thing really dialed in - but for standing, I'm still pretty tickled with it.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 3:32 pm
by ick
Seems like a pretty small and consistent shift at that distance. Seems like a keeper to me.

Would love to see photos of the setup.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 3:37 pm
by Jer
ick wrote:Seems like a pretty small and consistent shift at that distance. Seems like a keeper to me.

Would love to see photos of the setup.

Here ya go!

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Yes, I am aware the Front Sight is on backwards - it's done with intent.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 4:05 pm
by ick
Awesome.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 4:11 pm
by Bendersquint
Nice looking stick.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 5:34 pm
by Fulmen
Hard to say, but +1" POI at 25 yards is a little more than I'd like and I don't like the direction although that isn't a definitive sign that something is wrong. But then again unsupported shooting is more sensitive to trigger errors so it's really impossible to say anything for sure. Try again with support at 100' and report back.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 5:39 pm
by twodollarbill
Sweet!!!
I too like UBR's .... a little heavy for some :roll: ,
but they balance out a longer barrel nicely.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 8:03 pm
by Jer
Fulmen wrote:Hard to say, but +1" POI at 25 yards is a little more than I'd like and I don't like the direction although that isn't a definitive sign that something is wrong. But then again unsupported shooting is more sensitive to trigger errors so it's really impossible to say anything for sure. Try again with support at 100' and report back.
I'll be at a 100 yard range this weekend. I've got plenty of places on my turf to shoot, but the weather now is total crap and this place is covered. I'll run some comparison tests then also. I'll shoot normal - then suppressed / normal - suppressed to see if the POI shift is consistent and repeatable.

Shoulder firing IS a bit different with an extra 6" and several ounces...
twodollarbill wrote:Sweet!!!
I too like UBR's .... a little heavy for some :roll: ,
but they balance out a longer barrel nicely.
This. 1000x this. I've had several people who saw the build in photos tell me that it would be too heavy - then after they fire it, they understand. Yes, the build has about 8.5 lbs empty + mag and suppressor after that. But it is soooo worth it. :)

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 11:26 pm
by AkGun&ammo
Most of my POI shifts have been up and down. And on one rifle not enough to say it shifted. Waiting to get out with the newest rifle and get it sighted in and do the POI test.

Congrats on camera setup and new rifle.

Chris

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 11:30 pm
by AkGun&ammo
And Wahnssinn is correct.
sometimes orientation is important. On my m4, changing from my pencil mark makes the impact go up and down. I am trying to figure out a washer that will tighten up on non-susspressed impact. Haven't found it yet. Might settle for the two inches high have now at "hand-tight". Have to check it after firing a few though, it does un screw.


Chris

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 08, 2013 11:56 pm
by Jer
AkGun&ammo wrote:Congrats on camera setup and new rifle.
I'm sorry - "camera setup?"

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Thu May 09, 2013 6:10 am
by AkGun&ammo
nice looking photos.

Yeah, I know you can't tell I got a college degree or two. :)

Chris

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Thu May 09, 2013 1:35 pm
by Jer
AkGun&ammo wrote:nice looking photos.

Yeah, I know you can't tell I got a college degree or two. :)

Chris

I took the weapon photos while it was lying on the floor of my reloading room, with an iPhone 5....
The photo of the target was simply me tossing the target on my scanner and scanning it. :)

I wish I knew how to use a DSLR camera - but it has way too many buttons for me.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Thu May 09, 2013 7:06 pm
by Historian
Jer,

Congratulations, you certainly have a most enviable, pretty, and compelling set up.

To top it off your iPhone shots meet or exceed what we used to
do in the 1970's with a 4x5 SINAR-P view camera and hours in
a darkroom.

Please realize that my compliments come from a person
who personally has no weapon that is not all steel and snuggled in natural wood. :)


Best.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Thu May 09, 2013 8:31 pm
by ericlw
i just got my aac 762sdn6 few weeks ago. at 100 yards my remington 700 in 308 would bulls eye.with the suppressor;same everything it was 2 inches low.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Fri May 10, 2013 7:46 am
by Historian
ericlw wrote:i just got my aac 762sdn6 few weeks ago. at 100 yards my remington 700 in 308 would bulls eye.with the suppressor;same everything it was 2 inches low.
A way out thought.

Can the drop possibly be attributed to the added weight of the
suppressor on the front, dampening the normally unweighted barrel's
rising slightly as it normally would when unencumbered for which the
scope is set for?

Is there a real explanation that I seem to have not read?
Might do a test without the can but a weight hung on the end.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Fri May 10, 2013 12:39 pm
by JasonM
Historian wrote:
ericlw wrote:i just got my aac 762sdn6 few weeks ago. at 100 yards my remington 700 in 308 would bulls eye.with the suppressor;same everything it was 2 inches low.
A way out thought.

Can the drop possibly be attributed to the added weight of the
suppressor on the front, dampening the normally unweighted barrel's
rising slightly as it normally would when unencumbered for which the
scope is set for?

Is there a real explanation that I seem to have not read?
Might do a test without the can but a weight hung on the end.
The "real" explanation is that there is no definitive explanation.

It varies with every single setup. The shift you'll see with a particular setup is affected by so many variables- can's internal structure and design, barrel length, barrel profile, ammo, freefloat or not, torque of the muzzle device, etc, etc.

Add to that the physical variables- how perfectly concentric your bore/barrel are, how perfectly concentric the thread job is, how perfectly concentric the mount and the can are.

You can't predict with any certainty what direction shift will be in, even between otherwise identical guns with the same can.

The key is that for a particular gun and can, the shift will exactly repeat each time it's mounted.

Historian- yes, changes to a barrel's whip and harmonics from the added weight are definitely a factor.

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Tue May 14, 2013 4:46 am
by AkGun&ammo
Is there a way to garontee the shift will be the same each time you un-mount and remount the suspressor?

The one I have for my Tikka, moves up and down with where it is indexed. Am trying to keep my "pencil marked"- index mark oreinted the same each time. But sometimes I clean the mark off...

Torque???

Chris

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Tue May 14, 2013 5:43 am
by Tuukka
For testing POI shift, I would really recommend the following to elimnate the shooter induced variables as much as possible.

- Good support for the weapon ( prone, front and rear supported )
- Match Grade and regular ammo
- 100 yards or meters
- Enough magnification on the optic
- I prefer to use an MOA target, for example like this http://www.asesivut.net/taulu_MOA100m_ver2.gif

Of course groups can be shot with more sophisticated devices such as systems that fully cradle / hold the gun and the shooter is taken out of the equation, however the above is good advise for any regular testing.

Regards!

Tuukka Jokinen
Ase Utra sound suppressors

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Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Wed May 15, 2013 10:02 pm
by Iceman755
Question! How much poi shift does averybody have in general? I have 1.5 inch groups at 100 yards at full speed when I put my suppressor o. It's shift is horrendous. I needed up moving the target all the way up to 15 yards before I was even on target. I haven't attempted to see what it shoots like other than hand tight. So it could shoot high if rotated.. Anybody have ideas..

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Thu May 16, 2013 9:53 am
by Pman5KMO
FYI.... many manufacturers will void warranty for use of frangible ammunition....

Re: POI change suppressed v. un-suppressed - Is this normal

Posted: Thu May 16, 2013 5:55 pm
by Jer
FYI.... many manufacturers will void warranty for use of frangible ammunition....
YHM recommends against it - but they don't void the warranty.