I' m headed out for a two day rock chuck hunt here in Idaho that usually produces a large number of chucks each year.

In preparation for that I check my rifles that I will be using and today I found that my .223 26" barrel suppressed shooter was about a 1 1/2 inch higher than last year. Not difficult to correct but it made me wonder how that happens when I'm using the same components in the loads from the previous year and the indexed scope turrets show no movement. ?????

The .17HMR, I use for the close up work, was right on the money and didn't need any refinements.

Any thoughts on the change of point of impact? Perhaps a different moon phase......... or ..........the Coriolis effect has sped up ?

Wood stock??

I have the same question.
I took four varmint rifles to the range this week.
They are all mcmillan and HS precision stocks.
Used some of last years left over loads that are exactly the same as a year ago.
The rifles were all 1-1.5” high at last sight in, a year ago.
All of them needed some scope adjustment, not a lot, but up to 1.5”.
Not a big deal, but why are they not still sighted in?

Nope this one is also a McMillan.

I've had 10/22's also have this happen to them and those have been restocked with Hogue overmoulded and Elysium Barrels on them.

The mystery continues.........................

I've had the same thing happen, which is why I sight in my rifles every year before I hunt with them. I chalk it up to trying to keep ahead of the gremlins in the closet....

It’s global warming causing that!!!

I check my rifles before hunting season. Sometimes I have to adjust, sometimes not.

My hunting rifles have 4 and 6 power scopes and open sights. I always check before season. Only time they need adjustments is if I change the load.

I presume your 223 was sighted in previously with your can attached? Adding a can doesn't change accuracy but can change POI.

Any changes to the suppressor or torque on action screws? I'd also check the base and rings. I've seen that change the elevation and/or groups. Other that I'll blame the Russians

I notice changes in POI during cold weather sight in and it changes for warm weather. I have H335 for my warm weather shooting and RL7 for cold weather.

Light conditions, air density,wind - but more than likely something different in your bench set-up conditions. Like resting the stock at a different place on the forearm, gripping the stock differently,(tighter / looser etc).
I have encountered the same thing have usually been able to correct it by addressing / correcting something in my bench technique.

drover

What drover said.

Though will note that plenty of powders do not always work the same way at various temperatures. Which is why, living in Montana, I tend to use more temperature resistant powders than H335 and RL-7. Have enough rifles that using different powders for different conditions would be a real PITA.

Thanks for the posts, lads

Here are a couple of answers to questions posed:

1. The Can has been on that rifle for over 8 years

2. All action screws and scope mounts tested each sight in period with a Fat Wrench - all the same torque

3. I'm using RL-7 in those .223 loads

4. Bench techniques - Using the same equipment but might have changed resting points.... but not sure on this one - could be part of the answer


This is still a mystery unless my bench techniques are the culprit which could be the case. I'm liking the response of Climate Change the best!!!!!!!!!!

There is also the possibility that you may have unknowingly bumped the scope hard enough to have caused a change.

Give us an update next year.

drover

You said you were using the same components as last year, are these newly loaded rounds with those components or is this ammo that has been loaded for a time now?
Just curious.

Its the same ammo loaded the previous year for the hunt. No changes in the ammo part of the formula, thinking it might be the bench rest techniques.

It couldn't be shooter error.......................................right????

Even the neck tension on your ammunition can change after storing it for a length of time.
Gunpowder can absorb moisture.
Light conditions, wind, can change.
People who shoot competition without sighters are considered to be handicapped.
whelennut

Could even be case weld to the bearing surface of the bullet causing a rise in pressure. Usually occurs (I think) in new brass More than with used brass.