Many people have posted about how they can change the velocity, so I though
I'd share my ideas; some tried and tested, others just thought up.

- commercial velocity adjusters
  - velocity adjustable bolts; some require gun disassembly to adjust
  - velocity adjust valves; standard on some guns - usually externally
    adjustable

- other commercial adjusters
  - spring kits; several springs with different tensions or lengths.
    Longer and tenser springs hold the valve open longer, or just open
    it farther.  Common with pumps and older pistols.
  - power tube replacements; the power tube is the part that delivers
    the air through the bolt to the ball.  Some older pumps have different
    power tubes you can order that have smaller inner diameters, so less
    air is delivered.  (so-called "indoor" parts for indoor games)

- "Jurry-Rigging", reversable
  - careful placement of a thick washer or O-ring on the hammer where
    it strikes the valve can reduce the valve's open-time and how far
    it opens.  Added bonus: the action is not nearly as loud. (GOOD
    for semi's!)
  - placement of a urethane washer between the hammer and valve in
    nelson-based pumps will greatly increase air-efficiency, help
    silence the gun, and boost velocity, sometimes up to 75 fps.
    Custom-make one by getting a pack of URETHANE black washers
    (for faucets) at the hardware store.  Rubber will not work.
    Rubber-cement it into place.
  - reduced air flow.  Getting an on/off valve on your tank may help
    deliver less air if you turn it half way on.  This will not work
    if your marker has an expansion chamber, and could cause problems
    with some semi's. (cycling)
  - use  a muzzle brake.  A friend just got a little $8 piece of plastic
    that he was told would help the ball's accuracy with no decrease in
    velocity.  Yea, right.  Lowered his velocity by at least 50 fps.
    Don't ask me why -- I'm not sure myself. (didn't seem to help his
    accuracy either)

- "Jurry-Rigging", *permonant*
  (beware - if you reduce velocity too much, you'll have to visit
  the PB shop and replace the part(s) you modified)
  - holes in your barrel!  I've not tried this, but theoretically, you
    should be able to make some holes in your barrel, near the chamber,
    so some of your air vents instead of pushing the ball.  Drill with
    caution!  Spiral porting will have this effect as well, and many
    claim this increases accuracy.
  - clip your hammer's spring.  Take a side cutters and snip 1/8" of
    your big spring off.  Be sure not to remove too much -- it is
    suprising how much velocity a little bit of spring can take away!
    (if you can't find a spring kit, but CAN get a replacement spring,
    you can do this and MAKE your own kit; this is the best way)
  - make your own vel adj bolt or hammer!  You'll need a tap set to
    do this.  whichever has your power tube on it, you need to drill
    a hole in its side so that you drill into the power tube or into
    the hammer/bolt where the air goes thru.  Be sure not to drill
    thru an O-ring or any other threading parts.  Drill the hole to
    the proper size to match the tap and screw you are going to put in.
    It needs to be allen-wrench, but you can just cut a screw to the
    correct length and then cut a slot in it with a hacksaw for a small
    screwdriver adjust.  Adjust the screw so it blocks some of the
    airway.  Be sure, also, that if you are modifying the valve, that
    you put the hole "down-wind" from the valve seals and not down-wind
    of the "blowback" on a semi.  If the power tube or air chamber is
    fairly wide, select another place to put the screw, or use a
    larger screw.

Be careful when making any "permonant" modifications.  If there is any
question in your mind whether it will work properly after the mod, DON'T
DO IT, or ASK SOMEONE before trying.