Airforce Talon 177 best shot string

[Axel88]

Hi all,
I am starting to sight in my talon 177 and was wondering what power level would be best for around 20 foot pounds energy. I do not have a chronograph. I am sighting it in with 11.5 grain pellets but also have 16 grain pellets. Any advice would be helpful. I have it set at 5 power setting right now and it seems it drops from 3000 psi to 2000 with around twenty shots maybe less.
Any pointers would be great.

 

[shambozzie]

Adjust your start fill pressure and shoot groups. Start with 2800 psi and adj +/-.

 

[MongooseV8]

You are going to have to get a chronograph to really do any useful tuning. Everyones pcps are different and so are environmental conditions, and you might see different numbers than somebody posts.

With a non-regulated pcp you will see a speed curve depending on the air pressure and the valve/hammer design. To give you a rough idea, at full bottle pressure you will see lower fps and then as you shoot it will sharply increase speeds. After the bottle pressure and valve start to balance out you will see a more stable fps string until the air pressure gets too low causing speeds to sharply drop off. On the smallbore AirForce rifles you usually want to start with a fill pressure of ~2400-2800psi and shoot until the point fps drop off quickly. These parameters are also dependent on your power wheel setting as that changes the total hammer strike on the valve. For a Talon SS in 177 with a 20fpe target I would start fill pressure in the 2600-2700psi range and keep the power wheel around 75%.

Other than that you cant really know what your rifle is doing without a chronograph.