Time since loading reduces velocity

[kentsj]

Six months ago I loaded some 243 rounds. I then sighted them in 2.5 inches high @ 100 yards at 600 yards I was -10.8 MOA. I recently shot these same loads in similar weather and atmospheric conditions and my 600 yard correction was -11.9 MOA. Same gun, same scope, same setup.
Does the time since a round was loaded have such an effect?
Opinions please.

Thanks
Kent

 

[queen_stick]

I think the conditions were different. It's hard to tell if it changed, though it feels and looks the same. That's the only thing that could have changed right?

Maybe try loading some new rounds with the same recipe. Shoot the old ones and the new ones at the same range session, and see if they're different. The best way to tell would be to chrono the loads to see if the velocity changed. That would prove/disprove if it was the load or the conditions.

Walt

 

[Mikem]

Kent, I think if all else is the same, only the ammo temperature when fired, would make enough difference to notice. And some powders more than others, but not by time.

 

[yat3b35]

Six months ago I loaded some 243 rounds. I then sighted them in 2.5 inches high @ 100 yards at 600 yards I was -10.8 MOA. I recently shot these same loads in similar weather and atmospheric conditions and my 600 yard correction was -11.9 MOA. Same gun, same scope, same setup.
Does the time since a round was loaded have such an effect?
Opinions please.

Thanks
Kent

Funny you asked this question , as I asked one almost of the same nature over on Benchrest central and got an interesting answer. check it out http://benchrest.com/forums/showthread.php?t=68314

My question delt more with pressure signs and not velosity though.

 

[kentsj]

Thanks guys for all of the interesting opinions. I appreciate your time and efforts.

Kent

 

[blawton]

Yes same time of the year so the earth is spinning the same....

Sorry had too.

 

[kentsj]

It is not so much about the spinning as it is the tilt of the earth. The best time to test is at the equinox. I am in the process of developing a chart, for sale of course, that will give corrections for each day depending on the apogee of the earth. ;D
Really

Kent

 

[blawton]

Dont forget about the gravitational pull of the moon... ;D

 

[moorepower]

It would not take much in the way of headwind/tailwind change to see this at 600 yds.

 

[wapiti25]

case neck tension changes over time. Rounds loaded say a year ago some times will pop if you try to bump them deeper. There is a reaction going on between the bullet and case. When pulling old ammo, I found that it is better to seat the bullet a few thousands deeper before trying to pull. When I was shooting the national match course it was not unusual to be well outside the 10 ring a month later, conditions change.

 

[wapiti25]

I forgot to mention that air density is the bigest cause. This used to drive me crazy when hunting with a bow at high altitude, my sight would be off. Long rang hunters need to watch the barametric pressure as well as wind and mirage.