“The spring/piston airgun is the most fiendishly complicated machine ever devised by man”.
(The late Emeritus Professor of Engineering Mike Wright, Bsc, PhD, FRenG, FImechE, FIMA etc).
Attempts to understand what goes on inside a spring/piston airgun using logic are usually wrong, from fitting a beefier mainspring increases power (usually the opposite) to enlarging the transfer port allows more air to flow and raises power (plain wrong). Since the dawn of the Internet, people have been publishing their explanations of the springer shot cycle, and many of the falsehoods have gained traction, some becoming accepted as fact.
So, let’s take a look at what really happens when you increase piston weight (more properly piston mass). The subject of the test is my spare .177” TX200 Mk.3, modified to have 85mm of available stroke, running a factory mainspring and piston seal. The piston weighs 210g, and I tested it with and without a 27g weight, preloaded to give roughly the same muzzle energy, with Air Arms Field and Bisley Magnum pellets.
Logic would suggest that recoil displacement (travel) would be greater with the piston weight, yet the test reveals that the recoil was less with the weight. Logic would suggest that piston bounce and hence recoil surge would be less with the piston weight, but the test shows that it was greater with the weight. It is the pellet that has the greater effect on piston bounce, the Bisley Magnum producing far more bounce than the Air Arms Field.
Logic would suggest that the piston weight will compress the air to a higher pressure and, for once, logic is correct. Logic would further suggest that the higher cylinder pressure would result in higher muzzle energy and, as usual, logic is wrong. Why? The answer is that the piston weight is less good at slowing the transition from piston forward travel to bounce than spring preload, so the higher pressure is maintained for a shorter period.
I hope everyone finds this interesting, and conclude by suggesting that anything you read about the spring/piston airgun shot cycle on the internet is probably wrong assuming, as Miles Morris says, that you can believe this.
(The late Emeritus Professor of Engineering Mike Wright, Bsc, PhD, FRenG, FImechE, FIMA etc).
Attempts to understand what goes on inside a spring/piston airgun using logic are usually wrong, from fitting a beefier mainspring increases power (usually the opposite) to enlarging the transfer port allows more air to flow and raises power (plain wrong). Since the dawn of the Internet, people have been publishing their explanations of the springer shot cycle, and many of the falsehoods have gained traction, some becoming accepted as fact.
So, let’s take a look at what really happens when you increase piston weight (more properly piston mass). The subject of the test is my spare .177” TX200 Mk.3, modified to have 85mm of available stroke, running a factory mainspring and piston seal. The piston weighs 210g, and I tested it with and without a 27g weight, preloaded to give roughly the same muzzle energy, with Air Arms Field and Bisley Magnum pellets.
Logic would suggest that recoil displacement (travel) would be greater with the piston weight, yet the test reveals that the recoil was less with the weight. Logic would suggest that piston bounce and hence recoil surge would be less with the piston weight, but the test shows that it was greater with the weight. It is the pellet that has the greater effect on piston bounce, the Bisley Magnum producing far more bounce than the Air Arms Field.
Logic would suggest that the piston weight will compress the air to a higher pressure and, for once, logic is correct. Logic would further suggest that the higher cylinder pressure would result in higher muzzle energy and, as usual, logic is wrong. Why? The answer is that the piston weight is less good at slowing the transition from piston forward travel to bounce than spring preload, so the higher pressure is maintained for a shorter period.
I hope everyone finds this interesting, and conclude by suggesting that anything you read about the spring/piston airgun shot cycle on the internet is probably wrong assuming, as Miles Morris says, that you can believe this.
) of things you can share with us that will challenge our understanding and thinking 
(even if Im not enjoying my boinger atm)
