My gun was shooting at 1.09j with a 105 spring and 6.03 brass barrel.
The gun was accurate and straight with minimal power variations.
I changed out the barrel for a SS 6.02 zci and obviously the FPS went up to 1.33j.
I swapped out the spring to a 90 and the power settled around 1.06j but the BBs don't seem to be as punchy.
Is FPS equal? or would a loser bore and stronger spring be better then a tighter bite and weaker spring.
There are a lot of factors that have an effect on the physics of a ball being propelled out of a barrel
FPS is the velocity in ‘Feet per second’ of the projective, normally measured at the point of exit from the barrel
Joules are the measurement of the energy, and are calculated using the velocity and weight of the projectile
(Chronographs measure the velocity and particular chronographs can be set to display a joules value based on set weights of BBs
Beginning with the initial force imparted in the chamber from the spring and cushion of air, the projectile then accelerates along the barrel but also has friction resistance along the way.
It seems to be common sense to assume that as the energy being put into the BB is the same, that a heavier BB would be slower (taking more force to push the heavier weight) and resulting in the same energy coming out - but in reality the combination of everything can vary the results - and ‘joule creep’ becomes a term - that by changing one factor (the BB) can result in a greater resultant energy as the BB exits the barrel
………..
Loose (overbore) / tight (underbore) / matched bores all have their own effect inside the barrel ……. And then even the flight can have different experiences
My world is paintball, and we have those who swear by all of over/under/matched bores - and then we have different circumstances on how the paintball itself acts in the barrel -
With overbore a paintball could float on a cushion of air or bounce around - some of the air is ‘wasted’ but still contributes to how the ball flies
With underbore a paintball could be squashed (and if excessive can break) - when the paintball squeezes its way through the barrel all of the air behind it contributes to the energy imparted
…….
No matter whether it’s a plastic BB or a gelatine paintball, the initial muzzle velocity is just the start (and is the metric that complies with the rules)
The remaining velocity / energy upon impact varies based on its flight along the way. Which can also depend on how it went through the barrel and anything such as a hop up.
The energy could be maintained in flight, or it could quickly drop.
Optimum spin could maintain a ‘straight’ flight that hits (almost) where you pointed up to a set range then quickly drop, or you have a predictable curve that you need to compensate for at the targeted range - or it could just spray wildly in various random directions
