I have a shot string, now what?

[amccoy]

Please forgive my ignorance. Brand new to this...
Finally got my 1st ever airgun. Hatsan at44 qe long in .25 cal. Shot it for the 1st time today. I shot 36 shots through the chronograph (200 bar to approximately 100 bar). I did this to try and determine where this gun shoots best.
But I don't know how to interpret the shot string data. I really am trying to determine at which shot/pressure I want to start sighting in. I really have no idea what is an acceptable variation in fps for getting the pellets to hit at the same spot at certain yardages. Any input/advice would be much appreciated. I have no idea what pertinent info you might need to guide me but the following seems to me to possibly be important:

31.02 gr H&N Baracuda
1st shot was 781fps and velocity slowly increases to 840fps at shot 21. Then the shots begin to lose velocity- at shot 36 it was 754fps.

am I looking to stay within a certain avg velocity change thru certain shot numbers?? Just don't know what to do with this info.

thanks

 

[Cliff_Allen]

That sounds like a pretty normal shot string for that gun. If you're looking for a certain speed to sight in at, I'd pick the velocity that is right in between the high and the low. That way there when you're shooting at any given distance / target, you're less likely to be off in velocity by the full string between the high and low.

 

[Ginuwine1969]

The shot string just shows your power curve, usually when you start the FPS goes up then peeks then comes back down, its call your bell curve. If you first shot is 781 FPS then you want your last shot to be about the same, so look on your chart and see how many shots that equals. My guess is around 120 bar you should stop shooting or at 30 shots or so depending on your accuracy. You need the average FPS to use when you put the information in a program call Hawke Chair gun pro, along with pellet weight, scope height. It will give you a recommended zero for a given Kill zone (rise and fall of the pellet +/- half of inch is equals a 1 inch kill zone). Now you should shoot some groups and probably pellet test to see what is the best shooting pellet at 25 yards first then maybe 50 yards. You should not shoot lower than 30 shots to start off with while pellet testing and do groups of 5 to start off at 25 yards any group that is less than half of inch center to center or 3/4 inch group size from edge to edge should move on to 50 yard pellet testing. As alway JSB kings, heavy, and Air arms should be tested with your barracudas as well. Find out what pellet shoots the best, shoot another shot string with that pellet put the info in chair gun and use its zero or your own zero. (Good zeros for me are 19 close and 50 far or a 25 close and 38 yard far zero).

 

[TDK]

It all depends on how picky you are about POI change. A good place to start is 3-4% fps deviation from your peak, which I see thrown around often. For your string max of 840 fps, this is around 25-30 fps. You are looking to start at the pressure where you get ~815 fps and stop at the pressure when it drops to ~815 fps again. If you didn't write down the pressure throughout your shot string, you'll need to shoot another in order to translate shot# to pressure.

When shooting in the future, all you need to know is starting pressure (which is how much you will fill your gun to), and then number of shots that you get until pressure drops to your stop point. Fill to start pressure and shoot your X number of shots. With this as your default 'plan' you know where you have a consistent, accurate string of shots, and that you can probably squeeze a few more if needed from either side for a special occasion.