Well I managed to bring that thread to a screaming halt.... lol.Update on this one is I am now the once again proud owner of a sumatra 2500. At this point it is heading to Will Piatt for a fix and tune. I'll get it back after the tune and probably hold onto it for a long time now.Thanks again to all that chimed in to help the OP. Jeff
The first thing you need is a Chrony, When I got my new Sumatra I just started shooting it on High and couldn't hit the side of a barn. Without a Chronograph you are wasting time and pellets, believe me I know by making the same mistake your making! Penetrating wood is not going to tell you what you need to know!I found that when I cocked my gun open and adjusted the power it worked better as you have done. I also finally got the stubbornness out of me and got my chronograph out and shot some strings over it, I found that when the power was turned all the way down it would shoot a pellet about as fast as you could throw one, after 3 clicks up to the first Green dot from the lowest black dot I was getting around or just under 900 FPS with 25.4 grain JSB's and at 6 clicks up from the low black dot to the first red dot I was getting around 1100 FPS with the 25.4 grain pellets.I also found that shooting anything above the 1st Green dot with 25 grain or lighter pellets it will not group at all.Now upon testing the 33.95 grain JSB's I found that turning it from low up 6 clicks from the black dot to the first red dot I got 900 FPS and just under with excellent groups (Dime size at 50 yards) most of the time.Turning the Sumatra up all the way to what you think might be good is not going to work, I promise you that! It will more than likely be to fast even if it is not breaking the sound barrier, and it will not group well either.In all I found out that all I needed was the first 6 clicks up from the lowest power black dot and no further than the first Red Dot for max power and excellent grouping. You need to shoot all the 25 to 34 grain pellets at between 800 to 900 FPS and no further, at least that is what I found in testing my Sumatra .25 cal.The settings below give me dime groups at 30 to 50 yards if I do my part.JSB 25.4 grain = 3 clicks up from 1st Black Dot to 1st Green Dot for an average around 880 FPS +/-JSB 33.95 grain = 6 clicks up from 1st Black Dot to 1st RED Dot for an average around 880 FPS +/-Once you get over 1000 FPS you may as well hang it up because you are not going to get the Sumatra to group well anyway.My Sumatra loves JSB's The EUN JINS 43 grain will not shoot worth a darn in it.Say and think what you want, but this is what I found to be true in my New Sumatra and have done extensive testing with it for over a month with many settings and plenty of different Pellets and bullets. I spent a lot of Money and Time doing this so thats what I am sticking too Its a beast that's for sure Remember this as I have found out, just because that little wheel can go up another turn means absolutely nothing, except aggravation in wasting pellets, time, air and hard earned money!Also if I turn it up all the way I lose 50% or more of my shot count and gain no FPS what so ever to speak of anyway... as well breaking the sound barrier will only waste all your air and your accuracy will be very short lived.Good luck and I wish you the best,William