Suppressors POI shift w/ AA 762SDN6

[Drunktank]

Howdy Gents!

So yesterday I FINALLY got to take my new .308 savage precision carbine to the range and try it out and hot damn... that thing is way better than I'll ever be. However... Im having a few issues... one of them being the POI shift with my Advanced Armament 762SD N-6. I started dialing my scope in and I got close enough for now... I couldnt control my heart rate for crap and was sitting at 1MOA or so. But the interesting thing came when I mounted my suppressor after 40 rounds since a guy hopped on the lane next to me (too bad he had a 300WM deer rifle).

Once I mounted the suppressor my groups shifted damn near 2 inches down and too the right at 100yards. At first I was worried that the bullet was grazing the edge of the suppressor... that scared the hell out of me, so I popped it off and gave it a look and it was perfectly fine.

Granted, I expected a bit of a shift... but is this whats to be expected??? With a suppressor that expensive, Im pretty surprised. Or is this a sign of a bigger issue? Could I have screwed up the mounting of the AA 51T muzzle brake? granted I mounted this thing on my kitchen counter... but I used the shims provided by AA so I imagined its mounting could be square. Or possible cut of the mounting surface on the barrel isnt square? Also, I was using 175gr SMKs in new Win Brass from Southwest Ammo... if that means anything.

Whats everyones thoughts?

Im gonna try and make it back to the range this week and put some more ammo through it and get some pictures.

 

[JSTARSZ]

Re: POI shift w/ AA 762SDN6

That you have a POI shift when the suppressor is put on the rifle really doesn't mean anything if it is a consistent change. The 2 MOA shift at a 100 is within the normal range of a shift of suppressor on and off. Once you get the suppressor dialed in why would you ever shoot without having it on? That kind of defeats the purpose of having a suppressor. You should spend your time getting to know the suppressor and how it works with the rifle and look for variations between cold bore, first five rounds and when the suppressor gets very warm - What are the changes then?

Your suppressor is fine so don't worry about that issue.

 

[eracer]

Re: POI shift w/ AA 762SDN6

My understanding is that the POI shift is caused by the extra mass of the can hanging off the end off the barrel, altering its harmonics.

My 762-SDN-6 on my Grendel resulted in a POI shift of a full 4" low at 100 yards. But the groups tightened up. Which was cool.

 

[Drunktank]

Re: POI shift w/ AA 762SDN6

well damn... never figured that was normal for a shift! guess I wont worry about it then and work on developing some stuff.

JSTARZ - you're right... I dont want to shoot this thing without a suppressor... would defeat the purpose. However, this does double duty as a hunting rifle and some states I shoot in dont allow suppressors... like MO and CA. Since Im planning on setting this up with a 300 yard zero... guess Ill have to develop two zeros. Hopefully the ballistics will be similar enough that I can use the dope for both conditions.... guess we'll see! Cant wait to figure it out!

 

[Icallem]

Re: POI shift w/ AA 762SDN6

As I wrote saturday, just got mine also and tested them over the weekend. Shot Friday evening and POI was minimal, so dialed in and waited for Sat. morning to arrive.

Cold bore shot 1/2-3/4 inch high and next 4 in a bughole at POA. As I want to hunt with this rifle, cold bore is my concern.

Does yours mount up tight on the adapter?

Are the groups good?

 

[Icallem]

Re: POI shift w/ AA 762SDN6

I thought MO was fine using the can for hunting.

Hope so!!!

 

[JSTARSZ]

Re: POI shift w/ AA 762SDN6

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Icallem</div><div class="ubbcode-body">I thought MO was fine using the can for hunting.

Hope so!!!</div></div> I bet someone is looking it up right now

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Drunktank</div><div class="ubbcode-body">Im planning on setting this up with a 300 yard zero... guess Ill have to develop two zeros. </div></div> yep, two zeros is the way to go.

 

[JSTARSZ]

Re: POI shift w/ AA 762SDN6

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Icallem</div><div class="ubbcode-body">As I wrote saturday, just got mine also and tested them over the weekend. Shot Friday evening and POI was minimal, so dialed in and waited for Sat. morning to arrive.

Cold bore shot 1/2-3/4 inch high and next 4 in a bughole at POI. As I want to hunt with this rifle, cold bore is my concern.

Does yours mount up tight on the adapter?

Are the groups good?</div></div> Icallem - sounds like minute of deer to me...

 

[AACFAN]

Re: POI shift w/ AA 762SDN6

my cyclone has a 5" poi shift at 100 yards ... 26" barrel 22 ounces of lead sticking out front... no big deal however! it shoots great and repeats perfectly when taking it on and off .. so I'll never shoot without it anyways ... I think the SDN is pretty much a QD cyclone ... the internals are very similar ...

my Sdn just cleared .. time to go pick it up !!! enjoy!

 

[The Real Morpheus]

Re: POI shift w/ AA 762SDN6

I have a AAC 7.62 SD with the 51T mount on my Savage Model 10 Precision carbine in 308. POI shift is exactly 2" low at the six O'clock position at 100 yards.
http://i523.photobucket.com/albums/w352/morpheuscrna/photo.jpg

 

[Drunktank]

Re: POI shift w/ AA 762SDN6

Good to hear all this! Wish mine was just low rather than low and to the right... guess ya cant get all!

 

[uracowman]

Re: POI shift w/ AA 762SDN6

I never quite understood why people look so negatively upon a POI shift. I'd rather have a can that tightens up my groups with repeatability (with a poi shift) than a can that just keeps the same group with no POI shift. You can just readjust the zero....

 

[The Real Morpheus]

Re: POI shift w/ AA 762SDN6

I absolutely agree. It is an easy fix to just rezero.

 

[Icallem]

Re: POI shift w/ AA 762SDN6

I can't speak for everyone, but for me, I'm not concerned with a POI change, as you said that is an easy fix.

I would just like for it to start and stop with the same POI as POA.

After a few shoots, mine will print a group like this;

0
0
0
0
0

Tight enough that the holes cut each other, but not really what I was hoping for.

 

[eracer]

Re: POI shift w/ AA 762SDN6

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Icallem</div><div class="ubbcode-body">Does yours mount up tight on the adapter?

Are the groups good? </div></div>I'll comment. There is 'wiggle' when the 762-SDN-6 is attached to the 51T. I've been assured by AAC that there is no danger of baffle strikes, or loss of repeatability, and so far that's been true. In fact, my suppressed groups are tighter than my unsuppressed groups.

Having said that, it's a shame that the 762-SDN-6 won't fit on the new (soon to be released) 90T QD mount, which is being released to address the 'wiggle' issue.

 

[uracowman]

Re: POI shift w/ AA 762SDN6

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Icallem</div><div class="ubbcode-body">I can't speak for everyone, but for me, I'm not concerned with a POI change, as you said that is an easy fix.

I would just like for it to start and stop with the same POI as POA.

After a few shoots, mine will print a group like this;

0
0
0
0
0

Tight enough that the holes cut each other, but not really what I was hoping for. </div></div>

What can are you running? Do you group like that unsuppressed?

 

[Icallem]

Re: POI shift w/ AA 762SDN6

"What can are you running? Do you group like that unsuppressed?"

It is an AAC-7.62SD on a 51 tooth brake.

I have not had a chance to shoot more than 15 rounds at a time, but twice it has had the shots run up and down on 11-15. It is on a 20 inch MTU barrel. Without the can, it does very well. I'm not displeased with this one, as I want to hunt with it and the cold bore shot has been good. The other one does not lock up tight and I've not shot it yet.

 

[HPLLC]

Re: POI shift w/ AA 762SDN6

That would be good IMO.

My 762SD caused a 4.5MOA shift. The barrel was tornado threaded but the 18tooth mounting system locked up loose.