Impact = Crown = Dreamline = Impact

You have screw for regulation under barrel (over air tank) that set how far valve will open so you can tune air flow to the barrel.

Seems like the impact is better than the crown, I especially like the 700mm .30 Barrel. I may have to dive into one! 

When would that valve opening distance come to play on the Impact and can it be retrofitted to the Crown if needed at some point? 

The distance the valve open? They all work together!
The Impact doesn't have the transfer port adjustment.
So the Crown has the transfer port, and the impact has the valve throw adjustment.
2 different way of attacking airflow control.
Which one is better?????
They both have their advantages and dis-advantages. They both work!

The biggest issue to me is that the Crown wouldn't be practicle to put a 700mm barrel on it.

FX Makes great guns! The dreamline is more like the MKII & the Crown.

The Impact is in a different class when looking at design. (Not a better or worse class) Just different.

it basically stops the valve pin at what ever point you set it to make the air burst as short or long as you need to propel said pellet out the barrel.

Hola les voy a explicar como funciona el limitador de apertura de valvula esto mas que nada es un buen mecanismo para eliminar la variacion de fps y hacer qie su rifle sea lo mas contante posible. Recordemos siempre que la generacion de fps altos entre el conteo de varios tiros puede ser debido a que la valvula reguldora no funcione bien , mecanismos de el rifle como martillo etc y tambien los balines. Bien ahora vamos a lo importante , el impact trae un limitador de aperura de valvula y se debe utilizar de la siguiente manera 


primero vamos a eleguir el balin y mejor agrupacion que tengamos en cuanto a fps 

segundo una vez que tengamos los fps que deseamos que el arma tire por ejemplo 880 com jsb de 25 gr lo que vamos a hacer es reguitrar el limitador de apertura de valvula hatabque notemos que los fps bajen hasta 860 de esta forma estamos haciendo que el martillo tenga un poquito de golpe extra muy poco y el limitador solo retenga muy poquito la apertura de valvula de esta forma vamos a lograr un muy buen rendimiento en nuestra arma recuerden sienpre tener regulada la valvula de precion correctamente segun los calibres que usen 135 a 140 6.35 125 a 135 5.5 y demas que eso se encuentra en el manual aproximadamente en que preciones deben utilizarlas

"Michael" The Impact takes it a step further by allowing you to control how far the valve will open after the hammer hits it.

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That's interesting. Is this like the power wheel adjustment on the Sumatra 2500? I believe that's what the Sumatra does. It has a screw that dictates how far the valve stem can be pushed in.