Perplexing baffle strike issue

[boatbod]

Perplexing baffle strike issue (UPDATED: Big thanks to PDI)

My .22LR Coastal Passport suppressor is giving me some trouble, and I haven't yet figured out if it's the can or the gun.

When mounted on a Savage MkII, it performs great, but when mounted on a (new) P229 .22LR conversion it suffers continual strikes on the final baffle and front endcap.

The threads and shoulder on the Savage are snug and square respectively - probably because I cut them myself. The Sig barrel on the other hand, was factory threaded M9x.75, and is therefore fitted with the Sig 1/2-28 adaptor.

Before shooting, and again after noticing the key holing I visually inspected the alignment by looking down the bore. Even though everything appeared ok, I put the barrel in the lathe, dialed it in and checked the shoulder for square. Did the same with the adapter screwed in place, however the problem persists.

I've tried shooting Fed Automatch and SK Std+ ammo, both of which work fine in the Savage but not in the Sig.

Is it possible for ammo to cause the problem, or do I need to procure a snug fitting rod to accurately check the alignment of the suppressor itself? The only other gun in my possession presently threaded 1/2-28 is my ST-22, but I don't recall having problems with that when I last shot it.

As an aside, attaching the suppressor to either the ST-22 or the Savage causes a noticeable shift in the POI, both laterally and vertically.

Thoughts, comments, or suggestions welcome.

 

[CKOD]

On the guns without baffle strikes, put a piece of tape on the end, take a shot, smooth the tape back out and see if the bullet is leaving the endcap centered or is off center in the hole. If they are both off in the same direction, it may be a threading issue with the silencer. Of not, take a closer look at the sig.

 

[boatbod]

I did some further investigation with a PTG indicator rod, which was just long enough to pass through all 4 baffles when inserted in the barrel. With the endcap removed for visibility, it appears tip of the rod has approximately even clearance on both the Savage and Sig. I want to believe the Savage was ever-so-slightly better aligned, but it's hard to tell by eyeball alone, and certainly the difference did not seem enough to cause a strike.

Next, I checked the size of the holes through each of the four baffles to see if they were all the same. My guess is somewhere around 0.270". A 17/64 drill shank was too loose and 9/32 was too big.

The hole in the endcap is smaller than the baffles, and is sized at 0.250" across the hexagonal flats, primarily because it's designed to accept a 1/4" allen wrench to unscrew it from the tube.

Visual inspection shows the strikes to have been directed at one particular spot on the endcap. The baffles themselves are made of very lightweight aluminum, so anything more than a very slight brush from a passing bullet would be likely to cause instant destruction.

My impression is that maybe I need to check the tube and rear endcap's threaded shoulder for squareness, and if that checks out ok, will then consider enlarging the exit hole to match the baffles. Of course that would also require rethinking the wrench arrangements, but I don't think that's such a big deal.

I haven't yet tried the masking tape trick to see what happens when I fire a round though the can. It's dark now, so further trials will have to wait until Thursday.

 

[carryaglock]

PM Sent!

 

[Kharn]

Call Coastal, ship the suppressor and the P22 to them for inspection and correction.

 

[boatbod]

Call Coastal, ship the suppressor and the P22 to them for inspection and correction.

Marlin from PDI (a Coastal servicing dealer) is taking a look at some photos to see what needs to be done. I'd rather not ship the whole P229, but if needs be, I'm happy to send the .22 conversion barrel & slide.

 

[Kharn]

The barrel, thread adapter and suppressor should be sufficient, I missed that it was a conversion kit and thought the barrel was fixed.

 

[midcountyg]

Sounds odd to me to have a .250" end cap. That's asking for trouble. The end cap is the most likely place for a strike and usually has a hole at least the size of the largest baffle hole. I have a feeling you are striking on the others as well, just not as bad. From my experience 22lr rarely has a poi change. Like CKOD said, try the tape, it will help show you whats happening.

 

[boatbod]

I think it's scraping the 4th baffle and hitting the endcap.

The "index mark" referred to in the tape test picture is the alignment of the impact point on the inside of the endcap on the two guns tested.

Under close inspection, both guns exhibit some deflection towards the impact point, but obviously the P229 is far worse than the MkII.

 

[boatbod]

A big thanks Marlin at PDI for his patience, persistence and ultimate resolution to the problems with my can!

It turned out the primary issue was the Sig factory supplied 1/2-28 thread adapter not repeatably mating to the M9 barrel threads. After swapping that for a Coastal thread adapter, Marlin went on to completely rebuild the can with Coastal's new and completely redesigned baffle stack. The end result is a suppressor that is noticeably quieter, particularly with first round pop. I'm told the improvement is around 10-12db, which in my book is pretty significant!

Anyway, the best bit of all of this is that it didn't cost me a single cent. Marlin arranged a UPS pickup tag on his dime, and then did all the work for no charge. Talk about customer service! Way to go PDI!!!!

Now I just have to figure out how to send some business his way without the wife spotting "extras" in the gun room.

Thank you Marlin.

 

[Patrick]

Wow, that's good news and great service. I'll take a look at these guys. Thanks.

 

[Kharn]

decibels are are a logarithmic scale, every 3db reduction cuts the sound in half. So a 10-12 db reduction is between ~6x and ~12x quieter.