If anything it might slow down the rpf just a tad but it's barely noticeable, the only moderator donny fly recommends is the ronin along with donnys adapter, Google donny fly moderator for a hatsan blitz, my rife is a 25 caliber blitz bull pup but the enternals are all the same, first thing I did after receiving my blitz and after firing a few rounds was order the moderator, worst case senerio is you might have to get a lighter spring for the barrel at ace hardware, I didn't have to do that with mine because I increased the hammer spring adjustment one half a turn and it's been awesome ever since hope this helps check out donnys youtube video it explains everything