Impact shift from stock replacement

T

Tinybear

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Took ou my CZ 457 Thumbhole laminate this weekend. Had just swapped it into a MDT ORYX Chassis.

Found the rifle was impacting 4 or 5 mils low at 25 yards after swapping.

I expected a small change in impact (hence starting at 25 yards). but was shocked by such a large jump. Especially since both stock and chassis are very free floated. Scope was not touched.

Curious on the reason for this as it not making any sense to me. Rifle shot GREAT rest of day just a massive initial impact shift
 
Tinybear said:
Took ou my CZ 457 Thumbhole laminate this weekend. Had just swapped it into a MDT ORYX Chassis.

Found the rifle was impacting 4 or 5 mils low at 25 yards after swapping.

I expected a small change in impact (hence starting at 25 yards). but was shocked by such a large jump. Especially since both stock and chassis are very free floated. Scope was not touched.

Curious on the reason for this as it not making any sense to me. Rifle shot GREAT rest of day just a massive initial impact shift
Click to expand...
I would check to be sure the "recoil lug" is seated properly and not causing the action to sit crooked in the chassis.
 
Checked it all over removed stock rechecked All hood the lug is in correctly.

Impact point is remaining at the new location while in chassis. Haven’t placed back into the wood at this point to recheck.
 
Simply the torque on the stock screws changed and the point of impact changed. Adjust and if it is still impacting in tolerable groups be happy. If not go back to original.
 
Simple matter of physics how the action reacts when being held different and how the recoil pulse is handled in the new handle
playing with screw torques may change how it is but won't relate in any way to how it was
 
OkayShooter said:
Likely the bedding putting more pressure on the barrel, then with the wood stock
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It better not be putting pressure on the barrel, mine is free floated right up to the front of the receiver. I did not see much more than about a 1/2" in vertical, what I did notice was smaller groups right away.
 
If the scope has not been changed or touched, I'd be curious as to where in its adjustment range the crosshairs were set when the rifle is sighted in. Maybe the thing is now nicely centered while in the wood stock it was way off to one end of its adjustment range. In other words...maybe the rifle is now as it should be, and was experiencing a "problem" the entire time it was in the wood stock?

It seems more likely that a wood stock, regardless of bedding or pillars, would be applying uneven pressure/torque to the receiver than the metal chassis. I had a beautiful Anschutz 1432 in .22Hornet many years ago, a lightweight sporter with an eye-popping walnut stock. The wood in that stock continued to warp in weird ways over a period of years; it was bedded, and re-bedded, and re-re-bedded, and the barrel channel was hogged out a bit more each time. The gun was scary accurate...in terms of group size...most of the time...but the zero wandered around like a goat in a pasture. Wood can be fickle, untrustworthy stuff.
 
How it was sitting in the stock could be better or worse in either one. Unless you've got it bedded there could be stress. You might think this would be more likely in the wood stock since action screw torque is enough to alter how it sits in it. But a chassis isn't immune to inducing stress. Maybe it is machined well enough to have the action sit in there nicely, and maybe it isn't. Doing a nice stress-free bedding job in both stocks would be the only way to be sure. The wood stock would ideally get pillars, too.

The reason I asked about the weight first is because the lighter the whole gun is, the more rotation will be induced by the recoil. This might be more significant than bedding issues. Though bedding issues would be the second suspect, definitely.
 
Different stresses on the rifle at different points, subtly change the vibrations in the barrel and its position when the shot is "released". Impossible to replicate the precise mounting conditions between two stocks exactly. Its to be expected and isnt a big deal so long as accuracy is the same or better than the previous stock. Hell most people dont even realize, if you rest your barrel on something and fire you can also be off by a surprising amount, depending on the distance you're shooting at.
 
Yeah, I accidentally left a 2-gram bubble level on my barrel one day and started shooting and couldn't figure out what was wrong until I noticed it sitting there by the tuner. :D
 
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