Cocker pump efficiency

[BubbleGumBob]

As the title suggests wondering what sort of efficiency I can expect if I build one, thinking of building one for big game next year wondering if I could stay out for the whole 6 hours with one

Also what would be a cheap cocker to look for want it to be a centre feed with a flat asa not angled like some of these angled asa

Cheers

 

[Canon Fodder]

Should be about the same as an ego.