I posted this in my sidelever breech thread and would like to break it off as it’s own question/discussion. Some generalizations from reading about bv’s1. They are more tune able by vent and bv chamber size than by hammer strike. Primarily there change in power output by PRESSURE changes. over striking and too heavy of hammer creates over dwelling very quickly2. They work within a smaller tune window than hammer tuning but have the advantage of opening large valves with less hammer force.Not necessarily, they can be tuned over very broad range, but not by hammer strike alone 3. Maximum poppet lift is dictated by travel within the balance chamber then hammer bounce/crash occurs. Lift can be controlled via HEAVIER poppet spring preventing blow open, Larger or Smaller venting path to the balance chamber along with not having excessive hammer weight as stated above.4. A bv can ‘blow open’ and ‘hold’ open, but offers nothing to closing forceIf balance ratio gets to lopsided they turn into a DUMP valve. Stem venting from valves threat pressurizes balance chamber and help shut the valve. There is the KEY and trick to manufacturing and tuning a BV .... There are design parameters that must be in harmony for the "System" to work well. 5. The tuning of the ‘hold’ open is what gives us dwell Not exactly a Hold ... but a stalling of the open / close cycle from the initial opening and final closing. A correctly built BV that is not operating as a DUMP valve, never a point in the cycle where poppet just "Hangs" and flows being always in motion on it's way to max lift and then returning towards closure... This is how dwell is created by increasing or decreasing this time period.