Stoeger Stoeger, optics, moderators and POI shift. I'm stumped.

[JimD]

I could not find the parts diagram on line and the only disassembly videos I found were by Stoeger and only show the receiver, not the shroud or barrel. But the description multiple places says it has suppression which means, to me, the shroud has baffles. That means the shroud end cap the moderator screws into screws into the shroud, hot the barrel, I think. The shroud just cannot be loose and do what it has to do, including supporting a moderator. If it is loose, that would explain the POI changes.

 

[V5CVBB]

The Scout and Ranger are different from the Bullshark. The shroud has no grub screws. It fits on a round step at the receiver and is sandwiched between the receiver and barrel nut/mod adapter while putting the barrel in tension. A moderator screws onto the adapter, not the shroud. I have my shroud removed so I slid it back on to get pics.

 

[Evolve 3D]

The Scout and Ranger are different from the Bullshark. The shroud has no grub screws. It fits on a round step at the receiver and is sandwiched between the receiver and barrel nut/mod adapter while putting the barrel in tension. A moderator screws onto the adapter, not the shroud. I have my shroud removed so I slid it back on to get pics.View attachment 597331View attachment 597332

Why did you remove your shroud? What does it look like without it? Do you just leave it floated or have a band to support it?

 

[NotCutleryLover]

It is highly unlikely that the scope is at fault, particularly if it holds zero in between shots and during transport. This is likely a mechanical issue. You mentioned that the rifle returned to zero after removing the moderator/ re-adjusting the barrel.

I would keep remove the moderator and store the rifle as normal and after a day or two, test it out again. If there's no POI shift, repeat the test again with the moderator installed. I would also try both tests, but with the rifle's shroud/barrel not being under load during storage (for example, laying down in a case).
If there's a POI shift in either of the first two tests, but not when the rifle is stored horizontally, that indicates that some part of your shroud is taking a set from constant load. I'm not familiar with the XM1, but this could be due to a shroud being supported by soft o-rings that are compressed during storage.

The most likely candidate is just that screws on the shroud were loose. Shroud screws can often vibrate loose during shooting. I wouldn't loctite them, but you could try clear nail polish to give them a bit more resistance.

 

[Perle]

I use a Donny FL FX and it’s superb. No poi shift and hushes the bark.

Use a different moderator

 

[V5CVBB]

Why did you remove your shroud? What does it look like without it? Do you just leave it floated or have a band to support it?

I'm not convinced the shroud is best for accuracy. I removed it to see how the barrel shoots on it's own. If it's more accurate free floated, I may print a barrel band to mount the shroud but leave the barrel free. It looks better, less delicate with the shroud in place. It's a work in progress.

 

[JimD]

Thank you for the pictures, it really helps. The nut for the muzzle end of the shroud screws directly to the barrel? Are there any baffles in the shroud? If not, then the only sound suppression would be from the air exiting the muzzle and expanding inside the shroud. The bullshark has that but the air hits three baffles before coming out the muzzle. If it goes like this you have the shroud nut to the barrel plus the moderator to shroud nut potential looseness to potentially affect the POI. I always attach the moderator hand tight but you may want to consider using a torque screwdiver and/or putting a little blue lock tight on the barrel to barrel nut junction. I that nut loosened up and especially if the moderator was also not tight it could be the issue. You could also try different levels of tightness on the nut to see how if affects group size. I have a torque screwdriver I could use to tighten the nut onto the barrel with a specific torque. If you don't you might want to consider one. Tensioning the barrel is believed to make it more rigid. In theory it has an effect similar to a thicker barrel.

Taking the shroud off is an interesting idea. But if you are still using the shroud nut to adapt the barrel to the moderator you still have a chance for things to get loose.

 

[V5CVBB]

Thank you for the pictures, it really helps. The nut for the muzzle end of the shroud screws directly to the barrel? Are there any baffles in the shroud?

Yes, the nut/shroud retainer/moderator adapter, whatever you call it, screws onto the barrel. It stands off far enough from the crown to allow some air to exit the holes and into the shroud. No baffles anywhere. Not much of a moderator effect in my opinion. I'm fine shooting without noise suppression.

 

[JimD]

Well if you take off the nut/shroud retainer/moderator adapter you would eliminate that potential cause. I thought they were baffled only because some reviewers comment they are fairly quiet. If it seems like that might be the cause or at least a contributor another potentially useful change would be a barrel band to link the shroud (or conceivably barrel) to the airtube to stiffen it up and make it harder to shift. I believe the barrel is secured with a grub screw which is pretty standard but a grub screw is not an extremely robust way to fix the end of the barrel. If the barrel will rotate at all it would also mean that screw is loose. Big Air Precision makes barrel bands for my bullpups, he would probably make something for your Scout, it might even be the same design.

If you want to test the scope you could also do a simple tracking test. If you have a solid way to rest the scope (or gun with scope) you can just figure out how much a given number of clicks (like 25 or 50 or something) should move the reticle and then see if that is how much it moves. I did that test at the request of a scope manufacturer recently when I reported a drifting POI issue with their product. The error in tracking was about twice their expectation and I shipped it back. I seem to be having bad luck or something, I've had to send a couple good reputation lifetime warranty scopes back for this. It happens, at least to me.