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From: (Bartbob)
Newsgroups: rec.guns
Subject: Re: Free Float Barrels???
Date: 30 Nov 1995 13:44:23 -0500
Lines: 48

The reason rifle barrels need to be free from contact with
the forend is twofold:

First off, when the forend is held with one hand,
the forend bends and puts pressure on the barrel.  The same
thing happens when the forend is on bags at a bench.  As
the pressure direction and amount isn't consistant, the barrel
will bear against the forend with different pressures.

Secondly, the barrel whips and vibrates when the firing pin
strikes the primer and does so even more as the round fires.
The direction and amount that movement takes depends on
several things, such as how the bolt fits the receiver and the
case head bears against the bolt face.  If the forend is close
enough to the barrel to let the barrel bounce off of it, the muzzle
won't point at the same place for each shot.

It doesn't matter where the muzzle is in its movement due to
the vibrations and whipping.  As long as the bullet leaves the
muzzle at the same place for each shot, accuracy will be the
best.  There's a lot ot theories about the muzzle having to be at
the end of its movement to get best accuracy.  Nice theory.  But
until someone puts accelerators on the muzzle along with a bullet
detector to measure where the muzzle is when the bullet leaves,
they are just theories.  Most of the muzzle movement is caused
by whipping due to the recoil lug being below the receiver and the
forces going backwards in line with the bore.  This causes the
rifle to raise and bring the barrel with it; most of the movement from
whipping is vertical.  Some sideways whipping is caused by out of
square bolt faces and improper bedding.  Vibration is the resonant
movement of the barreled action and is much smaller in amplitude
than the whipping movement.  And remember that all the whipping
movement happens before the bullet exits the muzzle.

Over the years, it's been reinvented again and again; the process
of installing something in the forend to put pressure against the
barrel.  The designers hope to dampen the vibrations and whipping
in hopes that the bullet will exit the muzzle at the correct place.  As
these things have never proved successful, watch out for intense
advertising that promotes them.  Remember that when someone or
something is against the forend, these gadgets change their pressure
on the barrel and accuracy degrades.

And anyone who thinks the BOSS changes the harmonics of a barrel
to any significant degree. . . .         


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