The newest RAW barrels are twin ported, yes. That porting improves velocity 30-40fps depending on the rifle caliber, spring, and regulator setting with no other changes. A progressive hammer spring is a spring that has a varying twist rate of the coils, such that the initial compression is lighter, and the last bit of compression is heavier. RAW does this to lessen the initial cocking force before the lever opens and has its full mechanical advantage on the spring. 
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