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Discussion Starter #1
I had to re-zero yesterday after removing the barrel on my 17S to install the MI extended rail. After zeroing, I decided to see what the POI shift would be with my SDN-6. It shot about 6 inches low and three inches left in a nice tight group. Has anyone else experienced such a drastic shift with their SDN-6? I am wondering is I mounted the brakeout to the wrong torque specs. It did not seem to change the POI this drastically with 300 blk. Inspection of the can did not show any baffle strikes or other anomalies.
 

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One of the issues NSW dealt with.

Hence the switch to Surefire suppressors.

-SS
Sarge, is this mostly due to the gas flow/ internal baffle design(been reading your past post in regards to this, thx)? Since they're virtually the same weight, I would think the POI is not due to the usual suspect.
Can you elaborate further about the reasons and the POI of the Surefire vs. AAC vs. FN ECP? (OP hope you don't mind me tagging along, esoterica and technical discussion fascinate me)


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Poi shift happens with all suppressors some are better at it than others. The faster the bullet the more it will shift.

One of the reasons I picked a surefire over aac was the minimal shift in the surefires. I don't run my scar17 suppressed anymore as the wife has claimed the can as HERS. You can't fight city hall as they say.

Just write down your poi shift and dial it in when needed long as its repeatable its not a big deal.

Pro-tip: don't put your wife on the trust and you won't lose access to your nfa gear...

But she likes to shoot now so I guess it was worth it
 

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Sarge, is this mostly due to the gas flow/ internal baffle design(been reading your past post in regards to this, thx)? Since they're virtually the same weight, I would think the POI is not due to the usual suspect.
Can you elaborate further about the reasons and the POI of the Surefire vs. AAC vs. FN ECP? (OP hope you don't mind me tagging along, esoterica and technical discussion fascinate me)


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Here's an older thread that might answer some questions

http://fnforum.net/forums/scar-accessories-scopes-mods/26614-surefire-suppressors-scar-17-a.html
 

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The FN supplied suppressor experienced similar issues, albeit not as pronounced.

The easiest way to avoid shot correction would be to leave the suppressor on the weapon.

If you want a suppressor with minimal POI shift, the SF SOCOM-762-RC is worth a look.

Comparing POI shift from 300BLK to 7.62X51 with regards to velocity is misplaced theory. Barrel node and droop influence POI shift is where the issue is.

-SS
 

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Yesterday while shooting my Remington 700 AAC-sd with aac 762 sdn6 I had a distinct and repeatable shift to the 4-o'clock position of my POA.


I think all hosts interact differently with the POI impact.


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Discussion Starter #11
Sarge, is this mostly due to the gas flow/ internal baffle design(been reading your past post in regards to this, thx)? Since they're virtually the same weight, I would think the POI is not due to the usual suspect.
Can you elaborate further about the reasons and the POI of the Surefire vs. AAC vs. FN ECP? (OP hope you don't mind me tagging along, esoterica and technical discussion fascinate me)


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Not at all, I'm also very interested in this

The FN supplied suppressor experienced similar issues, albeit not as pronounced.

The easiest way to avoid shot correction would be to leave the suppressor on the weapon.

If you want a suppressor with minimal POI shift, the SF SOCOM-762-RC is worth a look.

Comparing POI shift from 300BLK to 7.62X51 with regards to velocity is misplaced theory. Barrel node and droop influence POI shift is where the issue is.

-SS
Great info as always Sgt, I appreciate you weighing in, SF


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Discussion Starter #12
I see that exact same shift (abit not so dramatic) . Low and left with my sdn6 and scar 17. Also not so much of a shift with 300aac as well
I want to sandbag it next time, or put it in a cradle and see how exact I can get it. Some of that spread is likely my poor shooting. While I would rather minimal POI shift, and maybe something like the surefire in the future, I already shelled out the clams for the aac, so as long as it's consistent I'm good with it. I'm certainly glad my can isn't the only one!

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Discussion Starter #13
Just write down your poi shift and dial it in when needed long as its repeatable its not a big deal.

Pro-tip: don't put your wife on the trust and you won't lose access to your nfa gear...

But she likes to shoot now so I guess it was worth it
That's all I needed to hear, I'm taking her out of my trust lol

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Wow !! I'm glad i stumbled upon this thread. My Scar 17 w/ AAC SDN-6 does the exact same POI shift about 2" left / 3" low . I have a AAC SD can but have not tried it yet on the Scar , will have to see if the POI shift is the same.
 

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Good thread here guys, here's my .02 cents with some pics. Shooting with a Geissele trigger, VCOG, AAC 51T Brakeout and AAC SDN-6. I tried 3 different sets of ammo, PMC 147gr, the cheap stuff, 168gr FGMM and i picked up some S&B at the range for another data point. I stock the PMC stuff since its cheap and decent .308 so i have more data points and as you can see the spread really opens up. With the PMC pic, what you are looking at is 20 rounds unsuppressed on the left and 20 rounds suppressed on the right, you can see the POI shift down. Not really much of a sample size, but surprisingly the S&B performed best unsupressed with a 1" group. On the S&B pic both targets have 5 shot groups suppressed and unsuppressed, again you can see the POI shift down. The FGMM performed the best suppressed with one of my suppressed groupings better than an usuppressed groupings. Have to chalk that up to luck and not doing my part as a shooter. Also in the FGMM pic you are looking at two targets both with 5 shot groups suppressed and unsupressed. Anyway, i remember when i was in the market for a suppressor and i wondered what the POI shift would be as well but i dont remember seeing any pics. Dont beat me up to bad on the accuracy guys, i am only a recreational shooter
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I think all hosts interact differently with the POI impact.
You hit the nail on the head right here. I could take several different guns of the same make and model and using the same silencer they would all have a different shift. What I have found is that it has more to due with the barrel threads than anything else.

Now having said that some silencers are known to have less of a POI shift than others and AAC seems to experience more shift because of the 51t mount. The 90t mount doesn't seem to have the same issues. Any silencer that uses a taper mount system (Surefire, Sig, Thunder Beast, Griffin Armament) have better POI shifts than others. However that doesn't discount the silencer companies that don't use a taper system.
 

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I know that this may sound a little remedial, but I have seen this happen if the suppressor is not firmly snuggled down and even checked from time to time. I know that it sounds silly but I have seen it happen. Also make sure the rockset or other attaching agent has not allowed the muzzle device to move and it is tight as well.
 

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That's about exactly how mine shifts. 168gr is definitely the sweet spot for ammo though.
Good thread here guys, here's my .02 cents with some pics. Shooting with a Geissele trigger, VCOG, AAC 51T Brakeout and AAC SDN-6. I tried 3 different sets of ammo, PMC 147gr, the cheap stuff, 168gr FGMM and i picked up some S&B at the range for another data point. I stock the PMC stuff since its cheap and decent .308 so i have more data points and as you can see the spread really opens up. With the PMC pic, what you are looking at is 20 rounds unsuppressed on the left and 20 rounds suppressed on the right, you can see the POI shift down. Not really much of a sample size, but surprisingly the S&B performed best unsupressed with a 1" group. On the S&B pic both targets have 5 shot groups suppressed and unsuppressed, again you can see the POI shift down. The FGMM performed the best suppressed with one of my suppressed groupings better than an usuppressed groupings. Have to chalk that up to luck and not doing my part as a shooter. Also in the FGMM pic you are looking at two targets both with 5 shot groups suppressed and unsupressed. Anyway, i remember when i was in the market for a suppressor and i wondered what the POI shift would be as well but i dont remember seeing any pics. Dont beat me up to bad on the accuracy guys, i am only a recreational shooter
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