In article ,
Jaques d'Alltrades wrote:
The message
from (Nick Maclaren) contains these words:

Boggle. Hang a wooden ball of known weight on the end of a string,
shoot the pellet into it, and measure how far it swings; that gives
you the momentum.

No it doesn't, unless your piece of string is of infinite length.

Well, I am sorry to say that you have forgotten your O-level physics.

Align the barrel with a spirit level, and measure
the dopy

The what?

The drop. God alone knows why I perpetrated THAT typo!

of height with distance; that gives you the velocity.

I've no idea what you mean. To get the velocity you have to measure both
the distance and the time it takes for the pellet to travel that
distance.

As JB points out, no, you don't. Sorry - O-level physics again.

Then you must allow for how much the pellet slows, or all you get is the
mean velocity over a distance, and the power of the gun must be measured
*AT* the muzzle, not halfway along any preselected distance.

No measurements are perfectly accurate. The methods I described
should be fairly easy to perform to 20% accuracy. My method for
estimating the slowdown due to air resistance is pretty inaccurate,
but the slowing effect is relatively small anyway (as you can
easily check), so the effect of the error on the final result is
even smaller.


Regards,
Nick Maclaren.