Hi folks,

I bought a new Steyr Hunter Scout auto about 2 months ago. It is a .22 and chronographs at 780FPS.  

I bought a like new longer barrel for it and swapped out the barrels just to see how I liked the longer barrel.  FPS was almost identical which surprised me. 

When I reinstalled the original (short) Scout barrel my FPS had dropped about 30FPS and spread was from 739-764.  I had not touched anything but the barrel and magazine. 

I cleaned the barrel (line with clean patches). No change. Then, even though I had not touched the power screw, I turned it 1/4 turn clockwise (tightened).  The FPS immediately went back to 783 (a bit higher than original) and Standard Deviation went from the 5 of before to 2.  But there is a definite "ping" sound now, hammer spring?  I have only been in air rifles for 5 years (I'm 64).  

The only thing that was a bit questionable to me in this swapping experiment was that there was no 0-ring on the longer barrel.  I contacted (e-mail) Steyr in Austria and they told me I didn't need an 0-ring for swapping barrels. But, the original, shorter scout barrel has a green o-ring. Did I do something shooting the longer barrel without an 0-ring to cause the spring tension to change thus the need to increase it?  Can I get rid of the ping by backing off say 1/8th a turn (halving what I had increased it by). 

Sorry about such a long post, but I was recommended to check here because there are lots of Steyr-experienced folks on this site.

Thanks

Roy