Originally Posted by
Solvo
The exit hole is essentially just the last baffle.
Reducing the size to suit .177 would certainly improve the performance...
The trouble is that for sub 12ft/lb air rifles there is so little air exiting the barrel that the different is somewhat negligible.
That's the main reason that most companies only off a one-size-fit-all option for air rifle sound moderators
Redesigning the shape of the baffles and air chambers can also up the performance, but there's always a cost; price, weight, accuracy etc.
It's usually a good idea to remember that the popular moderators on the market were designed by a bunch of skilled engineers and optimised for maximum results on a given budget.