Page 1 of 2

Suppressor POI Shift PS90 SBR

Posted: 23 Jun 2015, 10:14
by jhjenkins4th
I did some testing on the POI shift due to a suppressor mounted on my PS90 SBR 10.3”. On a previous trip to a public range, I zeroed my PS90 without a suppressor out to 50yds. When I attached my Specwar762 (with trifecta mount) to my PS90, it wouldn’t even hit paper.

This past weekend I went to my private range test some new reloads. So I set up my chronograph at 10ft and cardboard directly behind it, to confirm my rounds were not keyholing before mounting my suppressor. The PS90 was strapped tightly into a bench rest to prevent shooter error. Without suppressor, the shots hit tighly without keyhole. I then attached suppressor to the trifecta mount. I shot 2 rounds and the new bullet holes were hitting roughly 2 inches lower on the cardboard….at just 10ft!!!! Thankfully it did not hit the chronograph. Velocity was similar suppressed/unsuppressed.

This POI shift explains why I was not hitting paper on my previous range trip. This same suppressor on my 300blk AR15 has very little POI shift. I assume the size/weight of this suppressor combined with the skinny PS90 barrel may be causing the barrel to droop downward maybe… When I had shot my PS90 with a 22Sparrow a long time ago, I did not observe such a POI shift but did not really measure it either. My barrel was cut down by TROS a couple years ago and don’t think that is the issue at all.

For the remainder of my reload testing, I took the suppressor off and had great test results for my reloads. At the end of my session, I had some fun finishing off 2 mags of SS197 ammo I had laying around. I reattached the suppressor so I could see how the shots hit with the POI shift. The two mags being used were ATI brand and were both having multiple jams through the rapid fire session. At one jam a round failed to feed completely and resulted in a round with the blue tip ruined…so that round was discarded. After the session was over, I noticed that the Specwar had an end cap strike. I know there are not concentricity issues so it amazed me that this happened. The only thing I can think of is maybe another round got damaged during one of the jams caused it to keyhole. Thankfully the damage only appears to be cosmetic. No baffles were touched.


I think the jams were due to the ATI mags, as upon inspection they would not even feed the next round while messing with the rotary section with my fingers. Might be a combination of mag being dirty and weak mag spring, but the mags are nearly brand new. The mag I was using during reload testing was a FN brand mag.

Long winded but I just wanted to put my experience out there. I will not be running my Specwar on this PS90 any longer due to POI shift and possibility of another end cap strike.
Any input or thoughts are welcome.

Pics of the end cap strike
Image
Image

Re: Suppressor POI Shift PS90 SBR

Posted: 23 Jun 2015, 14:09
by DoubleJ
How much does the Specwar weigh?

Re: Suppressor POI Shift PS90 SBR

Posted: 23 Jun 2015, 14:13
by jhjenkins4th
24oz
https://silencerco.com/products/specwar/" onclick="window.open(this.href);return false;

Re: Suppressor POI Shift PS90 SBR

Posted: 23 Jun 2015, 14:28
by Ditch
Do you have one of the CMMG adapters there was an issue with concentricity issue with the first batch?
I have heard that SilencerCo repair times are fast when you send you item in, and my paperwork said that no questions asked on first repair.

Re: Suppressor POI Shift PS90 SBR

Posted: 23 Jun 2015, 15:13
by jhjenkins4th
The 1/2"-28 adapter came from TROS, from when hey chopped/threaded the factory barrel. Concentricity looks good when eyeballing the bore.

I will have to look into the Silencerco warranty. If it still functions fine with no POI Issue on on ther gun, it may not be work the hassle of shipping the suppressor back through my dealer that's 1.5 hours away.

Re: Suppressor POI Shift PS90 SBR

Posted: 23 Jun 2015, 15:47
by satellitedr3ams
Silencer Co. Had a can repaired and back in hand within 24 hours of sending it off before. Kenny is who took care of me, but I assume they extend this quality customer service to anyone. I recently had a end cap strike that look just like your from the suppressor being too loose. Good luck with your repair friend!

Re: Suppressor POI Shift PS90 SBR

Posted: 23 Jun 2015, 17:12
by Ditch
jhjenkins4th wrote:The 1/2"-28 adapter came from TROS, from when hey chopped/threaded the factory barrel. Concentricity looks good when eyeballing the bore.

I will have to look into the Silencerco warranty. If it still functions fine with no POI Issue on on ther gun, it may not be work the hassle of shipping the suppressor back through my dealer that's 1.5 hours away.
I believe you can go direct to them and you since it not a transfer.

Re: Suppressor POI Shift PS90 SBR

Posted: 24 Jun 2015, 18:24
by DoubleJ
jhjenkins4th wrote:24oz
https://silencerco.com/products/specwar/" onclick="window.open(this.href);return false;

Dang. I'm no PS90 expert, but I think you might be right about that much can on that little barrel. I've got a 6oz can on my FsN, and it's considered heavy in the 22LR world.

Re: Suppressor POI Shift PS90 SBR

Posted: 24 Jun 2015, 21:11
by panzermk2
The Gemtech SFN-57 is still the best all around can for the FsN. Not supposed to work on the P90/SBR PS90 but I had no issues.

Re: Suppressor POI Shift PS90 SBR

Posted: 25 Jun 2015, 03:46
by DoubleJ
It's a fine can for the FsN only, but my Axiom is slimmer, cheaper, can be disassembled and dipped, and uses a standard thread pitch for everything else out there. I've not been able to find a direct comparo between the two, so I can't say which is quieter, but a long stack of K baffles is tough to beat.

Re: Suppressor POI Shift PS90 SBR

Posted: 25 Jun 2015, 06:38
by Rapier1772
panzermk2 wrote:The Gemtech SFN-57 is still the best all around can for the FsN. Not supposed to work on the P90/SBR PS90 but I had no issues.
Says who? I asked Gemtech & they said as long as the thread size is correct, the suppressor would work fine. That's even posted on here somewhere.

Re: Suppressor POI Shift PS90 SBR

Posted: 25 Jun 2015, 11:59
by panzermk2
Rapier1772 wrote:
panzermk2 wrote:The Gemtech SFN-57 is still the best all around can for the FsN. Not supposed to work on the P90/SBR PS90 but I had no issues.
Says who? I asked Gemtech & they said as long as the thread size is correct, the suppressor would work fine. That's even posted on here somewhere.


Image

Re: Suppressor POI Shift PS90 SBR

Posted: 26 Jun 2015, 10:14
by Rapier1772
Ah, mine didn't have that on the box.

Re: Suppressor POI Shift PS90 SBR

Posted: 27 Jun 2015, 07:03
by jmz5
I spoke to gemtech several times about their cans over the years, there is no issue with it on the sbr the only difference between that can and the SAR-57 are the threads, they are the exact same internals.

Also Silco customer service is legendary.

Re: Suppressor POI Shift PS90 SBR

Posted: 30 Jun 2015, 13:47
by jhjenkins4th
I talked to Kasey with Silencerco over the phone. He said it wouldn't be a problem if I wanted to send the Specwar back, but if it is purely a end cap strike the performance/accuracy should not be affected. I figured I'd give it some testing the next time I get a yard pass from the wife to see if accuracy is still ok with my usual host, my 300BLK AR15. I'd rather save my one 'get out of jail free card' for any future situation that is more than cosmetic damage.

He did agree that the amount of POI shift I experienced was extreme and though it could be a threading issue. However, I told him I hadn't had any problems before shooting my Sparrow on the same host. He agreed that my explanation of the thin profile of the PS90 barrel with a 1.5 pound suppressor screwed at the end might be causing the barrel to bend enough to make this POI shift. I know the way that the barrel is fixed into the frame of the PS90 is not the most robust configuration...it is basically sandwiched into place with the nut at the end pulling it against the base of the barrel.

Re: Suppressor POI Shift PS90 SBR

Posted: 02 Jul 2015, 06:11
by towerofpower93
I too noticed a significant drop in POI when I attached my re-cored SFN-57 to my SBR'd PS90. While the re-core job only added a few ounces to the can, I think the fact that the barrel is not totally locked down onto the frame allows it to drop a substantial amount compared to other rifles when a suppressor is attached.

When I decided to re-zero the rifle with can attached I had to work in 10-20y steps from 10y out to 100y so I didn't get complete misses of the paper.

Going back to unsuppressed afterwards confirmed the large swing in POI as rounds were impacting well high at 100y.

Sucks to see an endcap strike, but it might have been a loose can. I check mine every 10-20rds while using a TROS thread adapter.

Re: Suppressor POI Shift PS90 SBR

Posted: 02 Jul 2015, 06:56
by jhjenkins4th
Thanks for your input tower. I had installed the FH with mild torque, since there is not much room to wrench. However, I always checked it before shooting. When I took it off yesterday, it still took a good bit of effort with sticking a screwdriver get between the FH prongs to break it loose. The prongs on the Trifecta mount are very thick, so I am definitely not worried about bending them....my screw driving shaft is what comes close to bending.

I went back with my FCS556 muzzle device and have no plans to suppress this gun with my Specwar now. I'm am pretty certain the suppressor weight is causing the POI shift. Heck, with my bare hands, I can ever so slightly move the barrel up and down in reference to the frame By pulling on the muzzle. The TROS 1/2"-28 adapter that holds the barrel in place fits in place fairly well but certainly not a super snug fit. I will have to grab a friend's PS90 and compare the fitment with my SBR. Curious if the factory barrel shroud provides a tighter fit than the TROS adapter.

Re: Suppressor POI Shift PS90 SBR

Posted: 02 Jul 2015, 13:14
by GONRA
GONRA wonders if its OK to install a suppressor with some MolyKote MoS2 "G" grease
OR just MoS2 dry powder, on the threads, to make Can removal easy?
Or will Can come loose too often? Bet you guys have tried this.....

Re: Suppressor POI Shift PS90 SBR

Posted: 03 Jul 2015, 06:23
by panzermk2
I use Anti seize.

It's designed to protect threads, be torqued, and not allow things to come loose unless you want it off.


It like to "walk" so use it sparingly.

Image

Re: Suppressor POI Shift PS90 SBR

Posted: 05 Jul 2015, 15:56
by jmz5
I use that stuff on my endcap threads to keep them from being carbon glued on, normal gun oil for my barrel threads as anti seize gets all over everything.