Hi Riaan,
The real factor limiting the loading on a gun is accuracy and what you
achieve by it. If you power a gun up the first thing you notice is the
increase in recoil. This will reduce your accuracy somewhat, but an
additional factor is the increase in barrel bending. The rail does help to
keep the point of aim constant, but what it can't do anything about is the
shaft whipping.
When fired from a powerful gun the spear bends a bit and comes out the
muzzle oscillating. This varies the point of aim randomly, but more
importantly slows the spear down. A very powerful gun seems to have a lot of
"power" but after a few meters the spear slows and reduces penetration in
the fish. The effort of loading those over strong bands was for nothing.
We have a graph of single band lengths that we use for various barrel
lengths. By loading with two bands you can increase the power, but not by
too much while still maintaining accuracy and penetration. We recommend two
16mm bands because of this.
We had a guy who overloaded his guns in our opinion. We measured the pull
and it was in the region of 90 - 100 kg. He lengthened the bands to about 60
kg and was much happier with the results. The average guy uses a pull of
about 45 - 50 kg with a single band on a 130 cm gun. We have never heard of
a gun misfiring without there being some fault with the mech or spear and
have never been able to test a mech except by loading a tray held by a
length of spear to about 150 kg ( in this case two people standing on it.
Cheers,
Jeremy
Dive Factory
181 Gale Street,
Durban 4001
South Africa
Tel: +27 31 3012241
Fax: +27 31 3012247
Email:
divefac@iafrica.com
Web:
www.roballen.co.za
