Thread: Some reasons why it often goes bad.

OK. Literally everything you said was wrong. Don't take offense, because we are only talking technical points here. Its Sunday morning, so here goes.

Originally Posted by LRP

Accuracy is the reduction of all variables to zero.
Accuracy is how "on target" you are. If you put out a 4mx4m target board, aim at the center and each round goes in one corner of the board, that is an accurate rifle. The point of aim is perfectly centered withing the group. If all four rounds landed in one hold in one corner, that is a precise rifle. If all the round land in the point of aim in one hole, that rifle is accurate and precise.
Reduction of variables is called target shooting. If you put the rifle in a tunnel in a machine rest with electronic primers, you have removed the maximum number of variables, including the shooter. Congratulations, you have removed variables to the point of absurdity. If the only thing you touch is a 2 ounce trigger, this is similar if you want to compare it to trying to shoot a deer.

Or at least as
close as us mortals can get them. One of these variables is where the
muzzle points as the bullet exits relative to the line of sight.
Is your scope attached to your stock? I'm willing to bet your scope is on the receiver and the barrel is screwed into the receiver. If these do stay as one unit, your have a problem.

That
pesky barreled action is like rubber; hard rubber laying on a chunk of
wood. Smack that hard rubbery thing with something and it's gonna be
bounced off of that piece of wood; but it ain't gonna come back down
to exactly the same place.
This is actually all that matters in bedding. It probably is going to come back to the same place

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.
Lots of rifles don't give a shit about bedding. Bedding a rifle often makes not difference, especially since not all bedding is equal. I have seen honest sub inch groups from a Winchester 30-06 that when lifted off the bench nearly fell out of the stock. The action screws were not done up. Some rifles bedding changes everything, some don't give a shit. Welcome to the world of harmonics.

When a rifle fires, its barreled action whips and vibrates all over
the place in every direction and various magnitudes
No it does not. Tuning a handload just harmonizes this vibration to a sweet spot for a consistent departure from the muzzle. If the action comes back to same spot in the stock (regardless of bedding) and your loads etc are consistent, then this "harmonic node" will be the same every time. See Brownings BOSS system for an attempt to control this.
. 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.
Again, is your scope attached to the stock or the receiver?

That is what causes groups (accuracy) to be
less than what makes smiley faces. Barrel weight doesn't reduce this
situation. Barrel weight is a great way to dampen harmonics.

Neither does handloads with extremely low velocity standard
deviations.
Depends on the size of your node.
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.
This is probably for true.
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,
Location of the action in the stock likely has an extremely minimal influence on the magnitude. Take a ruler and pull it between your fingers. The ruler will whip back and forward, initially with a high magnitude and low frequency, as it approaches the far end the magnitude falls and the frequency increases.

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.
As I have already alluded to, tuning these harmonics is all we are talking about here. You can have a thin whippy barrel and it matters not a whit if everything is tuned for that repeatable departure from the muzzle.

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.

A machine rest has dampers on it. Try putting the action in a bench vice and see what happens.



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.

BB

NEXT PART FOLLOWS ON


: .....it would seem that
: the inaccuracy caused by the necessarily loose fit of gun to shooter
: would overwhelm any looseness of fit in the rifle itself. Comments?
: Explanations?

I went through the receiver bedding stuff earlier. Now here's the
rest of the story.

`Bedding' a rifle to the shooter is equally as important. The rifle
must be held with the same pressure at all its person-contact points
just like the receiver in its stock-contact points. Here's why.....

After the bullet starts down the bore, Newton's Law becomes a very big
issue. The heavier the bullet, the more force needed to push it out
the bore. Seems the pressure behind the bullet also pushes back on the
inside of the cartridge case with about the same amount of force. As
a .308 Win. bullet goes down the bore and arrives at the muzzle going
about 2600 fps, the rifle has moved backwards about a tenth of an inch
as well as tilting upwards due to the center of the buttplate being
below the bore (hence pressure) axis. And it twists opposite the
direction of the rifling twist. How much it moves depends on how
firmly the rifle is being held; if tight, it won't move much at
all.

This movement is minimal and corrected for in sighting in. It is a constant or should be if your load is right. You can shoot good groups off a field rest with a free recoiling rifle. I'm happy to demonstrate this with my hunting weight 7mm rem mag if I can avoid more scope eye scars and its only 3-5 rounds.


If the amount of shooter-holding/resistance varies from shot to shot, there
is no way the rifle will move the same amount in the same direction as
the bullet goes from case mouth to muzzle. Therefore, although the
sights were dead center on the target when you heard the shot being
fired, by the time the bullet gets out of the muzzle, its path ain't
where you'ld like it to be.
Good luck with this

It takes about 3 milliseconds for a .308 bullet to go from case mouth
to muzzle. During that time is when the rifle recoils and whips about.
Some examples of what causes the bullet to end up striking the target
at an undesirable place are:

* Butt held too low in shoulder lets less mass be behind it; no shoulder
bone behind it, just flesh. The rifle's butt slips down a bit during
recoil which moves the muzzle end up. Bullet strikes high above call.

Almost the same thing happens with different shoulder pressure; it
causes vertical shot stringing.

* Cheek pressed hard/soft on buttstock changes resistance laterally or
vertically depending on pressure axis. Bullet will strike in any
direction away from call.

* Forehand held at different places with different pressure on forend;
all kinds of pressure point/axis differences. Amount of rifle movement
during bullet barrel time varies. Bullet strikes typically high and
low relative to call.

All of the above is better explained by harmonics. If you practice natural point of aim and the cross hairs rest naturally on the target, without any strain in any muscles, it is possible to shoot the rifles potential from awkward field rests. Any tension in your body will transfer to the rifle. If you are completely relaxed, you are like the dampers in the machine rest

A good example is shooting prone with a sling. Once in position,
do not move your front elbow; the one on the arm with the sling on.
Use your other hand to adjust sights, pet dogs, throw rocks at your score
keeper, but do not move that elbow. If it moves out of place only
half an inch, your next shot will be one-half MOA off call; move that
elbow one inch and the next shot will be one full MOA off call.

Natural point of aim. Don't hold on the target, align your entire body. Your control over the rifle is an illusion, your muscles don't fire at the speed of a gun. You will lose control of it if you are trying to control it.

* Pistol grip held differently for each shot. As the pressure applied
to the trigger gets transferred to the stock through the hand when
the sear releases, how that energy transfers to the stock while the
bullet is going down the barrel adds another dimension to where the
muzzle is when the bullet goes out. This is the main reason why light-
pull triggers enable the best accuracy; very little energy gets moved
into the stock and won't change muzzle position significantly. But
those four and a half ton triggers (sorry, 4.5 pound) on service rifles
used in competition.........no wonder it takes years and years for
most folks to master them. Three cheers for those 2 to 8 ounce wonders.

A good rule of thumb is to hold the pistol grip with hand pressure
equal to the trigger pull weight; at least. With heavy triggers, you
need to firmly grab the grip, otherwise, when a few pounds of force
slams back against the trigger stop, that firmer grip reduces the
amount of rifle movement the force causes.


All of which explains why free rifles have all those adjustable `gadgets'
all over them. Each part of the stock is adjusted to be a perfect fit
to the shooter's body. That way, the shooter's pressure on the stock will
be exactly the same from shot to shot.
All true, but not explained by controlling the whip of the barrel and action, only harmonizing it

And for those who marvel at those tiny groups benchresters shoot, even if
they are far back from winning anything.....well a great number of them
shoot free recoil; the rifle just rests on sandbags, then the thumb and
forefinger squeezes that 2-ounce trigger, the rifle goes bang and recoils
exactly the same amount in each direction. Every single shot. There is
no shooter contact with it except for the trigger. But that shooting
style isn't done in other disciplines. You gotta hold onto that magnum
you're gonna bust an elk with this fall; and that magnum moves about twice
as much before the bullet exits.

Rifle stocks are nothing more than an interface between the barreled action
and the shooter. Both things on either side of the interface vibrate and
move all over the place. If that interface is well fit to the metal at
one end and the flesh-and-bone thing at the other end, [COLOR="#FF0000"]all the variables
of their fit will be reduced to zero[/COLOR
In order to reduce the variables to zero, both the rifle and the shooter need to vanish. You can't reduce all the variables. Just get rid of unnecessary ones while tuning the important ones. A lot of people remove relevant variables from their shooting in practice then wonder why they struggle when all those variables return in the field. If you have not practiced dealing with a variable, you can't manage it.

or pretty darn close that is.

BB

END OF QUOTED STORY

So when someone with a powerhouse heavy-recoiling super light bangstick says it does quarter moa all day just smile and say "great"
People do this as a matter of routine. The weight of the rifle is irrelevant for accuracy and precision, it simply amplifies the need for the shooter to their part as a shooters errors will have more effect when transferred to a rifle with lesser mass. The world is now full of light weight bug hole shooting magnums and people who fire them at small targets a long way away from field rests
.