Starting from 1993, blow back system was incorporated in airsoft pistol.  Front liners like MGC Glock 17 series and JAC Hi-power invaded the market with such system which is wished for long from shooters.  And the fixed slide generation started to fade out.  Although MGC and JAC are the first manufacturers to put blow back system on the market, their success can never match Magna blow back system from Western Arms.  WA debut its Magna blow back system in 1994 with its Beretta 92F.  Such system is highly rated as it performs very well in accuracy, recoil, reliability, blow back timing and consistency.

Until now, it is still the top system in the market. WA patented the design and other manufacturers like Tanaka and New MGC
are paying WA in order to produce guns with Magna blow back.  Carrying such system in the market truly add credits to the gun.

Magna Blow Back is powered by pressurized gas from magazine.  Gas is controlled by the lower frame and blow back force is generated in the slide.  Actions in slide can be divided in 4 stages.
 
Stage 1

Floating Valve is pushed backward when BB bullet is in chamber.  Gas is diverted to power the BB.
 

Stage 2

When BB is fired, floating valve is back to its original position, diverting the gas to the rear part.
 

Stage 3

Powered by the gas, slide is pushed backward and blow back is taking place.
 

Stage 4

Whole Loading Nozzle is pulled back by the spring on the top and process completed.
 

Gas flow is controlled by the frame and 4 stages took places:
 

Stage A

Top view of the frame with magazine attached
In ready position, hammer is locked and magazine is attached.
 

Stage B

Hammer down and striking the firing pin, firing pin then hit the valve to release gas.
 

Stage C

Firing of BB and blow back take place in the slide.
 

Stage D

Return of slide presses the Valve-lock release, supply of gas is stopped, and a cycle is completed.
For blow back system, Magna do provide best trigger pull, recoil feel, accuracy and reliability.  In fact, the magazine (gas release) system is under continue modification to attain satisfactory level at present--the type R magazine.  When I was playing with my fixed slide M93R, I just can't imagine something like Magna blow back will exist.  If Magna is a new generation of airsoft gun, what will the next generation be?
 

Note:
Magna blow back is patented by Western Arms
Spain Patent No. ES2,098,845
Canada Patent No. 2,133,145
Europe Patent No. 0,647,825
Australia Patent No. 669,276
US Patent No. 5,476,087 / 5,477,843 / 5,655,510 / 5,664,552
Japan Patent No. 2,561,421 / 2,561,429 / 2,561,444 / 2,587,906 / 2,597,829