I removed my FX Impact X barrel to clean, and as I was putting it back, i realized that once the barrel goes into the slot, there is some minor "rotation" play. Since this aligns the transfer port, i figured every small rotation will ever so slightly align/mis-align the transfer port between the barrel and the port.
So, I shot over the chrony as i experimented with tightening the barrel at both ends of the "rotation" and realized there is a "better" alignment end. The counter-clockwise end gave me an extra 8fps than the clock-wise rotation end consistently on an average of 10 shots over chrony. I think, for my FX Impact X 700mm barrel, setting the barrel counter-clockwise before tightening the barrel screw aligns the transfer port better than the other directions.
Your barrel might be different, but i gather it is worth trying it out for your own Impact/Crown to get more fps and consistency. Don't even need to remove barrel, just loosen the barrel retaining screw a little, rotate and shoot over chrony to check fps, find the most FPS "setting" and re-tighten. That's it.
So, I shot over the chrony as i experimented with tightening the barrel at both ends of the "rotation" and realized there is a "better" alignment end. The counter-clockwise end gave me an extra 8fps than the clock-wise rotation end consistently on an average of 10 shots over chrony. I think, for my FX Impact X 700mm barrel, setting the barrel counter-clockwise before tightening the barrel screw aligns the transfer port better than the other directions.
Your barrel might be different, but i gather it is worth trying it out for your own Impact/Crown to get more fps and consistency. Don't even need to remove barrel, just loosen the barrel retaining screw a little, rotate and shoot over chrony to check fps, find the most FPS "setting" and re-tighten. That's it.