Lighter piston , better FPS ??

[Basu]

Dear IFGians,
this is understood that more is the weight of the piston , higher is the momentum when it hits the far end , resulting in more labour for the main spring , thus the time taken to compress the air will be more. the result apprently seems less FPS. I would request fellow IFGians to share their experiences in respect of indians and imported guns.

Basu

[brihacharan]

[quote="Basu"]
Dear IFGians,
this is understood that more is the weight of the piston , higher is the momentum when it hits the far end , resulting in more labour for the main spring , thus the time taken to compress the air will be more. the result apprently seems less FPS. I would request fellow IFGians to share their experiences in respect of indians and imported guns.

Hi Basu,
> Good question!
> First of all when air guns are designed the 2 main criteria considered are:
1. The laws of physics
2. Precision engineering.
> As you would realize the "OPTIMUM' power / velocity + accuracy can be achieved only when the gun's delivers via the pellet an fps of between 800 to 900fps. Beyound this the weapon will lose its accuracy.
> To achieve this there exists a ratio between the tube & piston's dimensions + metallurgical composition of material used for these.
> Hence within these confines a spring is seated - again the metallurgy of the wire used to make the spring, the no. of coils to fit the piston / tube dimensions + annealing treatment given to the spring to retain its resilient quality etc play an important part.
> True that if the swept volume is increased it should result in more air being compressed - achieved by shortening the piston - but then it goes back to the efficiency of the spring to push forward the piston to take advatage of the excess volume of air - CATCH 22 SITUATION!!!
> The best thing to do is calculate the weight lost by reducing the piston size & compensate it by putting a Top Hat / front spring guide. Mind you this is a 'Rule of the Thumb' solution. It could work!
> Also velocity depends on the pellet weight & its construction.
> Remember most foreign air rile makers claim velocity by using PBS (Performance Ballistic Alloy)pellets. These pellets are known to deliver 20% more fps - but their accuracy is questionable. It's a "Marketing Gimmic".
> Lastly take your gun to a skilled mechanic / tuner - add whatever you want to viz: a new synthetic seal, a new spring, a new rear spring guide, modify the piston + piston rod + a Top Hat & adjust the trigger to suit your desired pull.
> With all these if you manage to get 750fps to 800fps using a good quality round head pellet in 14.5grs and get a group within 1" at 30ft - WELL YOU GOT YOURSELF A GREAT GUN!!!
Happy shooting -
Cheers
Brihacharan

[shooter]

informative. thanks for sharing.