I think it is bolt speed you are looking for. Different guns have different bolt speeds. Some travel at a higher feet per second than others. I think most blow forward designs are anywhere from 10 to 25 feet per second. Although not proven, it would seem that a slower bolt forward design would be "more gentle" to fragile paint.
I'm sure we have all seen markers that instead of chopping a ball, it just stops the bolt and wedges the ball between the feed neck and face of the bolt. I think it was a cocker I saw this in and possibly pbjosh's shiva he designed. I am not sure how this works, but it may be related to the pressure operating the cocking mechanism, not the pressure used to accelerate the ball down the barrel.
kila
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