Silencer PIO shift

[Lancer]

Hi there fellow shooters
I have come across a strange problem and just putting it out there to see if anyone has come across the same thing??

I shoot with a FX M3 30cal 700mm barrel just so you know

Anyhow I have tried 5 or 6 silencers on it and all shift the POI a lot. I mean 6" shift left right up down depends on the silencer
is this normal?? or is something going on I dont know about??

 

[Mr.H]

6" is a lot. Have you inspected the baffles to check for pellet clipping?

 

[OldSpook]

Hi there fellow shooters
I have come across a strange problem and just putting it out there to see if anyone has come across the same thing??

I shoot with a FX M3 30cal 700mm barrel just so you know

Anyhow I have tried 5 or 6 silencers on it and all shift the POI a lot. I mean 6" shift left right up down depends on the silencer
is this normal?? or is something going on I dont know about??

6 inches at what range?

 

[Sqwirl57]

POI shift with a moderator is normal. 6" does seem excessive but depending on your range it may not be. If the groups are still tight I wouldn't suspect clipping but if they opened up significantly or you're seeing fliers I'd say you have your answer

 

[JaceSpace1369]

Hi there fellow shooters
I have come across a strange problem and just putting it out there to see if anyone has come across the same thing??

I shoot with a FX M3 30cal 700mm barrel just so you know

Anyhow I have tried 5 or 6 silencers on it and all shift the POI a lot. I mean 6" shift left right up down depends on the silencer
is this normal?? or is something going on I dont know about??

Is it everytime you bring the gun out to shoot? If so make sure your barrel screw it tight and the the barrel is seated all the way. 6 inches in either direction is not normal. I had this happen to me not with a moderator but when I had the huma tensioner kit on, everytime I went to shoo the gun, depending on what side the gun was laying before shooting the first 3 or 4 shots would be 4-6 inches to the right or left. And with my leshiy classic .22 if I shoot slugs it will shoot 7-8 inches left and pellets will do the same to the right.

 

[beerthief]

check ALL the screws !

 

[dens228]

Most silencers have changed my POI. But the POI was still consistent. Unless there's clipping.

 

[Lancer]

50 yards is the distance
No clipping
Have tried several different silencers
Groups are still good sometimes even better

 

[Vetmx]

Not unusual. Go with the one that produces the best groups.

 

[Airgunmann]

You should have it so it's set for high or low hits and not left or right hits be easier to sight in and on at farther ranges

 

[B_y_r_o_n]

50 yards is the distance
No clipping
Have tried several different silencers
Groups are still good sometimes even better

Problem solved, choose the one that produces the best groups.

 

[seanfrev]

It's interesting to read your post as I discovered an issue with accuracy with my buck rail yesterday on my bara 1100 z. Shooting in my backyard with the moderator has given me very sporadic results with sometimes decent groups and other times very sporadic and wide. As a last resort I took the moderator off and my groups all of a sudden became dime-sized punching one jagged hole. I called Buck rail they told me the Barra 1100 z has some issues with air flow when the moderator is on it causing accuracy problems. I've reached out to barra and I'm waiting for a reply. So depending upon the air rifle you could have point of impact differences as well as accuracy issues when using a moderator.

 

[OldSpook]

It's interesting to read your post as I discovered an issue with accuracy with my buck rail yesterday on my bara 1100 z. Shooting in my backyard with the moderator has given me very sporadic results with sometimes decent groups and other times very sporadic and wide. As a last resort I took the moderator off and my groups all of a sudden became dime-sized punching one jagged hole. I called Buck rail they told me the Barra 1100 z has some issues with air flow when the moderator is on it causing accuracy problems. I've reached out to barra and I'm waiting for a reply. So depending upon the air rifle you could have point of impact differences as well as accuracy issues when using a moderator.

The rifle does not have issues with accuracy. The moderator does. The rifle is shooting dime-sized groups. The moderator is not.

 

[seanfrev]

Yes i see your point. Well said.

 

[LDP]

The rifle does not have issues with air flow. The moderator does. The rifle is shooting dime-sized groups. The moderator is not.

Yep its a bad baffle design if the rifle is accurate without the mod but bad accuracy with the mod if clipping isnt the issue.

 

[steve-l]

There are three issues that are unfortunately far too common that can cause this. The first is clipping caused by moderator misalignment with the barrel. This is most common when the moderator adaptor fastens to the shroud. This can easily be checked by using a rod the exact diameter of the barrel lands inserted through the mounted moderator. If everything is square the rod should be centered in the moderator bore. A simple but very effective tool. The second issue that can cause accuracy issues is poor baffle design. As a pellet exits the barrel the propelling air will be deflected off the back of the pellet and to the side out accelerating the pellet. This air will reach the baffle before the pellet and can be reflected back into the pellet's path. If the baffle is not symmetrical, it will exaggerate the effect even more. An inverted cone baffle is superior to all other designs in my experience. One more point to consider. If the air gun uses a plenum chamber, a good performing moderator will attenuate the pellet velocity a small amount. Poor moderators do not. This velocity loss is due to the fact that the column of air in front of the pellet is also attenuated reducing the differential pressure across the fired pellet. The third reason is barrel droop due to weight of the moderator hung on the end of an unsupported thin wall barrel design, like the FX rifles. Simply readjust the gun's sight to compensate, it is not a problem.

 

[subscriber]

Yes, the alignment rod works to show moderator misalignment with the barrel bore, but not everyone has a rod sized just right for their barrel; nor one made of non-marring material. So, something we all have access to and is non-invasive may be almost as good: Masking tape applied over the muzzle face of the suppressor, slightly embossed with your finger to make a nice ring imprint. Then you shoot through the tape to see where the hole is relative to the ring embossed in the tape. A wadcutter helps, but is not essential. Usually, you can shoot a few shots without blowing off the tape to confirm system stability.

You can also look through the moderator after unscrewing from the other end after shooting through the tape one or more times - see image below.

Now, if you suspect large enough misalignment to cause clipping, then the rod is better because no shooting is required to get a reading. If you don't have a rod, you can look through the mounted moderator and barrel from the front end, with the action open, and a light source at the breech. If your PCP has an easily removable bolt, then do that and look through the barrel from the breech. Else, the practice of inspecting a barrel from the muzzle with the action locked open, is standard for rifles such as the Garand and the M14; as scary as that may be. It is also how you tell that your lever action barrel is not obstructed, should you accidentally drop it muzzle down on soft soil while on a hunt. Better to look, than shoot out potential muzzle obstructions while hoping for the best.

Both the rod and the tape will show misalignment, but not the cause. That is for you to diagnose. Tightening the moderator on shims that clock it a quarter turn at a time will help you to identify if you are dealing with a problem in the moderator, or the airgun barrel stud, or adaptor. Is the offset rotationally phase locked to the moderator, or the airgun barrel, shroud, or adaptor?

Thanks to @TorqueMaster for sharing this simple but effective technique with me. Here are two of his images of a custom extended shroud insert I designed. One, showing a pellet hole slightly off center in the masking tape; indicating the need for some diagnostics.

 

[bucketboy]

To the op, the liner crush nut can rotate when moderator are screwed on and off, also the design of the liner system is not as rigid as a standard barrel so heavier mods will drag the barrel down more and all weight of mods will alter the harmonics..the longer the barrel and higher the power the worse the effect becomes.


A simple test for moderator concentricity is to sick a piece of masking tape over the moderator end cap and take a shot, look to see if the pellet exit hole is dead centre to the moderator bore.

Bb