molder,
Pellets obviously have to travel out of the barrel as centered and as straight as they can..
When a suppressor is added, you'll need to be sure that it is 100% in-line with the barrel,
so that when the pellet travels through and out of it, the pellet doesn't accidentally touch the sides..
If/when this happens, it's known as pellet-clipping [since the pellet clips the side of the exit-hole]
Suppressors can be used flawlessly, and then can also cause issues as far as point of impact variations
and/or the clipping issue previously mentioned..
I have several suppressors, and have only had one instance of clipping on a certain rifle..
The way the threads mated, the suppressor ended up tipping to a side - just a tiny bit - but, that was just enough..
The points of impact went from 1 single hole at 10m to looking like I'd shot the target with bird-shot out of a saw'd off shotgun. lol
Some suppressors have end-caps, so you can loosen them a bit, spin the center, then re-tighten..
This will re-align things [indexing] That can be a quick fix.
Other times you might need to get more MacGyverish. I used a very thin nylon washer between the barrel and the suppressor,
and another time, I used an o-ring, and that 'adjusted' the way the threads caught just enough to resolve the clipping issue.
A rule of thumb.. To help eliminate the possibility of clipping issues..
Use One-Size-Up [for the diameter of the suppressor hole] for the pellet size you'll be using.
Ex: if you're shooting .177, use a .22 suppressor.
If you're shooting .22 cal, use a .25 suppressor.
Hope that helps a bit.

Sam -