Reasons for Bedding an action and free floating the barrel.
By Bart Bobbitt
Examining the difference between a stock without epoxy bedding and one
with epoxy bedding for the same barreled action, we note that when the
epoxy bedded stock is used groups (scores?) are excellent. But when
the plain stock is used, scores (groups?) are horrible. Even when the
same ammo is used. So, there must be a reason. There is Bedding.
When a rifle fires, its barreled action whips and vibrates all over
the place in every direction and various magnitudes. Such physical
trauma results in the receiver finally settling down in a microscopically
different place after each shot. After which it now gets to start
the vibrating and whipping all over again when the next shot is fired.
But that microscopically different starting point causes the barreled
action to take off in a different direction and magnitude than before
when the next shot is fired. This just repeats for each and every shot.
As the muzzle points in random places for each shot due to these whips
and vibrations, it will point at a different place relative to the line
of sight for each shot. That is what causes groups (accuracy) to be
less than what makes smiley faces. Barrel weight doesn't reduce this
situation. Neither does handloads with extremely low velocity standard
deviations. It is further aggravated by out-of-square bolt faces and
locking lugs not making full contact. If the barrel touches part of
the forend, that adds another accuracy-degrading element to an already
bad situation. And the best cases, primers, powder and bullets so
darned perfectly assembled won't help either. If the barreled action
doesn't start from the same place for each shot, the bullets won't end
up in the same place later.
So, if the barreled action can be somehow returned to exactly the same
place in the stock for each and every shot, the magnitude of those
barrel whips and vibrations will be greatly reduced, if not practically
eliminated. Then the only thing left is normal barreled action vibrations
at their resonant frequency, but this can't be eliminated although it
has virtually no effect on accuracy. Epoxy bedding was and is the
solution.
With the proper epoxy material being a near zero-tolerance fit to the
receiver, there's no room for the receiver to move around in from shot
to shot. Clearance between the receiver and the epoxy is .0001-in. or
less. That tolerance is at all places around the receiver. With
the correct torque on the stock screws, that receiver will go back to
the same position with the same tension so darned repeatable from shot
to shot that the accuracy is the equal of a barrel clamped in a machine
rest with just the action hanging on the back end.
Benchresters moved one step further some years ago. After expoxy bedding
their receivers, they removed the barreled action, roughed up the bedding
surface and the receiver, then glued the stock to the receiver. That
made sure the barreled action started its high-on-the-Richter-Scale moves
from exactly the same place, plus it eliminated the need to check the
stock screw torque a few times during the shooting day.
If one does not reduce the physical variables their own body has as part
of the complete shooting system, they may be large enough to mask any
improvements that have been made to the rifle and/or ammo to make the
mechanical parts of the system a flawless performer. Sometimes, that
does happen.
GC