Even hammers used as tools eventually fail, but what would you choose to use as a demolition hammer, the simple two part one, or the one that comes with an air condition cab?
If the Maverick was improved upon as was the impact(s), there would be less sales because Maverick owners would only buy the improvement mods.
Why did FX go up to 89 cc plenum then back down to 79 cc plenum? It's a matter of what the bean counters decided would be the best profitable route.
For example, using quick and dirty round numbers, accurate and exact numbers will be provided in my book. let us say that we want 50-foot pounds of energy (fpe) at the muzzle from whatever projectile. The energy efficiency, we'll call at 5 fpe per grain of air. Note: (447.013692 grains of air at any temperature, or pressure makes up one mole (the mole: Avogadros Number: exact by definition is 6.02214076 x 10^23 entities, being daltons, atoms, molecules, eggs or cars, as it is just a quantity, or a number like a pair, a dozen, a score, a myriad etc.) of air molecules). I hate putting parentheses inside parentheses, unless for clarity. So, our 50 fpe projectile will require 10 grains of air to propel it to a velocity that will give it 50 fpe at whatever our mind experiment barrel length is required.
Further note: at our mind experiment temperature, one grain of air has a theoretical maximum of approximately 10.26 fpe, and according to the law of conservation of energy and momentum, 5 fpe per grain is a tad less than 50% of the theoretical limit, which means that the longer the projectile stays in the barrel on its path, the more momentum transfer it can receive from the air molecules, but the total momentum of the air and projectile can never decrease or increase in totality, and because of the 6 degrees of freedom, only 1/6 of the air molecules will be striking the projectile per time. Picture a cube, the projectile only occupies one of the 6 faces, while the air molecules are striking all 6 faces internally.
For the geeks, like myself that need a number to work with. Use a 28.5 grain projectile at 888,9543234 fps, which will give you 50 fpe at mean sea level and 45-degree latitude. Do not attempt to check this value at high tide because you will get wet.
After thought: 10.26 fpe x 10 gr-Air = 102.6 fpe between the projectile 50 fpe + 52.6 fpe of the air.
For the shot count at 50 fpe using 10 grains of air:
{(250 Bar - 150 Bar) x 14.504 x 1.24 x 0.480 liter } / 10 gr-Air = 86 shots
It needs a stronger and heavier hammer and spring and HS compression turns.
{(250 Bar - 133.146 Bar) x 14.504 x 1.24 x 0.480 liter } / 10 gr-Air = 101 shots
It can use a lighter hammer and spring with less HS compression turns.
Duhhh!
Note: both 79 cc and 89 cc plenums hold the same amount of gr-Air (213.121776 grains)
P1 x V1 = P2 x V2 = 213.121776
I prefer to use grains of air for efficiency
than cubic inches of air per fpe because the energy in an average air molecule is only dependent on the absolute temperature, which I love when YouTube air gun reviewers note the ambient temperature of their review; else, its just another opinion and snake oil. The variable "1.24" is a constant at a specific temperature where I convert from imperial units to metric and back to imperial because who uses cubic inches in their "tank" volume?
The tricky part is the conversions that I do not agree, but by law they have been defined, so to keep everyone on the same page we use the accepted norm by law and definition.
1 kilogram = 2.204622622 lbs by law, but by the laws of physics it is closer to 2.20462262184879
1 inch = 2.54 cm by law; even though, 25.4 mm is the same, it is not 2.54 cm. NASA learned that the hard way after a $2 billion dollar boo-boo.
The universal gas constant (R) for imperial units is 53.343, and uses the Rankin scale
(459.67R = 273.15K = 0 celcius = 32 Fahrenheit).
1 second in time = 9,192,631,770 Hz of Ca133 ground state at zero kelvin
Any many more variables come into play with air-gunning, so don't limit yourself.
Now, lets take the 79 cc plenum at 150 Bar pressure (2,175.6 psig).
WARNING!
A little math follows that would take up 3 old school chalkboards, but here is the crunched version with explanations on the derivations in my book, to follow.
2,175.6 psig x 1.24 x 0.079 L = 213.121776 grains of compressed air in the 79 cc (0.079L) plenum.
We need 10 grains of air, so 10/213.121776 = 0.04692153091, or roughly 4.7% of the air stored in the plenum under a 150 Bar pressure.
Now we take the 89 cc plenum, which holds who knows and who cares because we only need 10 grains of air, so we will reverse engineer it.
psig x 1.24 x 0.089 = gr of air total in 89 cc plenum
10 gr-Air / gr-Air-total
Keeping the same percentage value:
10 / (1.24 x 0.089 x 0.04692153091) = 1,931.150562 psig, or 133.146 Bar regulator pressure.
In conclusion, we went from 150 Bar to 133 Bar to achieve the same fpe, and the drop in Bar pressure will allow us to have more shots in our count, and less stress from the higher pressure of 150 Bar, so why the down-size? It is simple, it is $$$.
The difference in time it takes 10 grains of air to go through the valve on the 79 cc 150 Bar regulated plenum compared to the 10 grains of air to go through the valve on the 89 cc 133 Bar regulated plenum is so small that we would need a high-speed digital storage oscilloscope with very expensive piezo electric pressure sensors to see the difference. The air velocity of the pellet verses the air velocity of the air to the speed of sound through the barrel is 1:2:5, or less than 1 millisecond, or close to since the valve open dwell at our 50 fpe is open for less than the first 3 inches of pellet barrel travel, which is at the highest g-force acceleration.
I'll say it for you: Wow!
I would love an FX Impact M3 in 25 caliber with an 800 mm barrel, 580 cc cylinder to 300 Bar, an 89 cc plenum then shoot my projectiles just below Mach 0.8 with the use of a fixed 10 power telescope with mildots and the little light squares to adjust for windage and elevation than to move the turrets. He with the fastest algorithm, lives to shoot another day.
Thank you for your comment as it stimulated the remaining juices between my ears and now that I flash a light in one ear, the light does not come out the other ear as clear.
I love this forum as I have been learning a lot from it and the conversations.
Lastly, for you folks that get annoyed at long winded dialog, this one is for you...
Uhhhggg...!
FJB Out!
Well... — NOW I know that my brain was never intended to master that kind of math or physics. Just like a motorcycle was never intended to drive on a river....
Francisco, you (and some others here at AGN) are amazing whizzes. 
WOW! 
