> Can you tell me the differences between a closed bolt and a open bolt and 
> perhaps refer to the Vector as an illustration. I don't see how a pump 
> which I assume is a closed bolt gets supposedly superior action over an 
> open bolt of a semi.

You have to look at the gun when it is waiting for the trigger to
be pulled.  If the bolt has closed and the ball is currently in
the barrel (not in the chamber) then it is a 'closed bolt system.'
Any gun that awaits firing with the bolt withdrawn and the ball
just in the chamber is referred to as 'open bolt.'

These two ideas produce different conditions for the balls when fired.
Most (but not all) closed bolt systems have an o-ring on the bolt
that will help seal the chamber shut so that less gas is wasted
when firing.  Since open bolt systems need to get their bolt opened
again as fast as possible, the o-ring is almost always removed, because
the friction with the barrel on the o-ring is enough to slow it down
considerably.

I have heard lots of people making unfounded claims about closed bolt
systems; here are a few of them:

- they deform the ball less
- they are more gas efficient
- they are more accurate
- they break less balls

With the exception of gas efficiency, (and only to a *slight* degree)
all the rest are meaningless.  Open bolt designs, however, as a tradeoff
for that little bit of gas efficiency, are usually able to cycle just
a _hair_ faster than closed-bolt, and in my opinion, chop less balls.

If the operator pulls the trigger too fast on most open-bolt guns, the
trigger pulls that were too short will simply not do anything.  On closed-
bolt guns, 'short stroking' tends to chop balls. (a 'la automag)