JimPlas
Super member
The HW 95 has so much going for it - light weight, good balance and a great trigger. On the minus side are the stock ergonomics and especially the recoil, but we can improve the later.
Recoil is largely a function of the weight of the piston and the weight of the rest of the rifle. The HW95 piston weighs in at 270g, and the rifle weighs 3.4 Kg.
The weight of the piston contributes to its momentum, or quantity of motion (a measure of how much force is needed to bring it to a halt) and, when it does come to a momentary halt at the end of the compression stroke, the piston's weight contributes to its inertia, in this case resistance to change direction of travel under pressure from the air.
So, a heavier piston compresses the air more, and for a greater length of time, and we are going to reduce that weight, and replace it with something else. To reduce the piston's weight involves drilling holes in it. As the piston body is case hardened, it's necessary to grind away the surface where you will be drilling. I reduced the weight of my piston to 190g.
To make up for the reduced piston weight, I'm using Welsh Willy's 34 coil HP mainspring. This spring will push the piston slightly less far, so compressing the air slightly less, but the 50 lbf of preload will keep the piston in the vicinity of the cylinder end for longer, providing sufficient pressure to get the pellet up to speed.
So what do we end up with? The free recoil of the standard rifle with a 500g scope is 6.6mm, more than the HW97, HW77, TX200, Walther LGV and LGU. With the light piston, that reduces to 4.86mm, less than the HW97, HW77, TX200, Walther LGV and LGU, all of which the HW95 will now comfortably outshoot.
Recoil is largely a function of the weight of the piston and the weight of the rest of the rifle. The HW95 piston weighs in at 270g, and the rifle weighs 3.4 Kg.
The weight of the piston contributes to its momentum, or quantity of motion (a measure of how much force is needed to bring it to a halt) and, when it does come to a momentary halt at the end of the compression stroke, the piston's weight contributes to its inertia, in this case resistance to change direction of travel under pressure from the air.
So, a heavier piston compresses the air more, and for a greater length of time, and we are going to reduce that weight, and replace it with something else. To reduce the piston's weight involves drilling holes in it. As the piston body is case hardened, it's necessary to grind away the surface where you will be drilling. I reduced the weight of my piston to 190g.
To make up for the reduced piston weight, I'm using Welsh Willy's 34 coil HP mainspring. This spring will push the piston slightly less far, so compressing the air slightly less, but the 50 lbf of preload will keep the piston in the vicinity of the cylinder end for longer, providing sufficient pressure to get the pellet up to speed.
So what do we end up with? The free recoil of the standard rifle with a 500g scope is 6.6mm, more than the HW97, HW77, TX200, Walther LGV and LGU. With the light piston, that reduces to 4.86mm, less than the HW97, HW77, TX200, Walther LGV and LGU, all of which the HW95 will now comfortably outshoot.
