My non "goof off" time this morning has been spent shooting and tuning my Stoeger Bullshark in 22 caliber. The wind was very low before 8am this morning so I decided to try another target with the AEA 18.3 grain pellets it likes. The weather report says it was only about 2mph. I shot a three shot group I will post (it's on the left in the picture) and it was a great little one hole group. So I was excited to see if I could get a 200 on the 30 yard Master target. Instead I shot a 195 with 17Xs, That might be my highest X count this year but the 7 is a concern as are the two 9s. Even more of a concern is the 40 fps velocity variation over the 20 shots. I noticed previously that I had to adjust my point of aim with this gun during the target but I was not measuring velocity then and did not know why, The chronograph explains the need to adjust. I then shot a much more raged one hole group on the right of that photograph with the hammer spring increased half a turn. I was trying for a simple retune. Group isn't too good so I decided I need to do a real tune.
I grabbed a tin of FX 18.1 grain because I have very few AEAs (I'm out right now but more are to arrive today) and the bullshark shoots them pretty well. I went up 2.25 turns of the hammer spring screw to it's maximum setting and velocity increase to 920 fps. On the 195 target it went from 837 to 877. On the warm up shots it was as low as 815. So I expected it to go up with more hammer spring but the amount was a bit of a surprise. The last 1/4 turn hammer spring actually decreased velocity establishing the 920 as the absolute peak. So I calculated 95% of that to get 875 and backed off the hammer spring enough to get about there. I shot 3 shot groups at this setting and up a little and down a little from that point. I ended up going down a little, like 1/8th turn, from that setting but the resulting velocity it's at now is very close to 875 average. At the end I switched back to AEA 18.3s which gave me a little higher velocity and I tested a bit but ended up lowering the hammer spring 1/8th turn which brought them down to about 875. Then I shot a 30 yard challenge target with them at this setting. Velocity variation on that target was from 867 to 888 fps. ES about half what it was on the 195 target. I got a 199 16X. Wind had increased to 4mph which is still low but was enough I was adjusting my POA for it but the velocity variation was minor enough I don't think it affected the point of impact at 30 yards. My other SPA guns have had lower ES than this but it may also settle in some with more shooting. I'm happy to have found a tune that is accurate without a high ES.
I grabbed a tin of FX 18.1 grain because I have very few AEAs (I'm out right now but more are to arrive today) and the bullshark shoots them pretty well. I went up 2.25 turns of the hammer spring screw to it's maximum setting and velocity increase to 920 fps. On the 195 target it went from 837 to 877. On the warm up shots it was as low as 815. So I expected it to go up with more hammer spring but the amount was a bit of a surprise. The last 1/4 turn hammer spring actually decreased velocity establishing the 920 as the absolute peak. So I calculated 95% of that to get 875 and backed off the hammer spring enough to get about there. I shot 3 shot groups at this setting and up a little and down a little from that point. I ended up going down a little, like 1/8th turn, from that setting but the resulting velocity it's at now is very close to 875 average. At the end I switched back to AEA 18.3s which gave me a little higher velocity and I tested a bit but ended up lowering the hammer spring 1/8th turn which brought them down to about 875. Then I shot a 30 yard challenge target with them at this setting. Velocity variation on that target was from 867 to 888 fps. ES about half what it was on the 195 target. I got a 199 16X. Wind had increased to 4mph which is still low but was enough I was adjusting my POA for it but the velocity variation was minor enough I don't think it affected the point of impact at 30 yards. My other SPA guns have had lower ES than this but it may also settle in some with more shooting. I'm happy to have found a tune that is accurate without a high ES.
