Winter load vs summer loads

[dkhunt14]

You'd be doing load development all over again.

My LR hunting 284 has a 4.5 moa come up at 400, with a 200 yard zero...at 70 degrees. 2875 FPS.

My last 2 trips to the range this past week (including today) were 10 degrees above zero. Needed 5.5 moa to get it right. 2830 FPS.

So the temp change, and the effect of a 60 degree temperature drop to the loaded ammo (in my range bag in the back of my truck), made a moa (4") difference in just those 200 yards!

Losing only 45 feet per second velocity, that seems like a lot of difference in elevation. I believe there were other factors involved. Air density, head to tail winds, humidity or other weather related things. Maybe even barrel timing. I have shot loads at 1000 yards and even 50 or 100 more fps didn't make that much difference on the same day. Matt

 

[Depart123]

You'd be doing load development all over again.

My LR hunting 284 has a 4.5 moa come up at 400, with a 200 yard zero...at 70 degrees. 2875 FPS.

My last 2 trips to the range this past week (including today) were 10 degrees above zero. Needed 5.5 moa to get it right. 2830 FPS.

So the temp change, and the effect of a 60 degree temperature drop to the loaded ammo (in my range bag in the back of my truck), made a moa (4") difference in just those 200 yards!

The temp change alone would only account for an inch or less at the distances you mentioned. You had some other things going on as well, most likely a zero shift due to the temperture affect on the gun itself or a drastically different light condition. Light alone can make a 1 moa difference or more.

 

[yukonal]

I believe there were other factors involved. Air density, head to tail winds, humidity or other weather related things. Matt

All those factors were certainly involved to add to the drop.

I've gone thru these changes for 5 winters, with two 284's that I've built for LR Hunting. They both have reacted the same, shooting in extreme conditions. Minimum of a half moa change, up to 1 moa. Depends on ALL weather conditions, and how long loaded ammo has sat in the back of the truck in 0-10 degree weather. I've kept track with notes, and can refer back.

Good thing is...I always have the range to myself!

 

[yukonal]

Yukonal,
I'm thinking load development in the warmer months 70 to 95 degrees and adjust MOA for the slower FPS in the winter months. I'm wondering going this route maybe keep a better group than doing the load development in reverse? To keep pressure down when it warms up.
A Leaphart

That's exactly what I do. A ballistic app will do a pretty good job of adjusting the info, but not perfect. You still have to confirm the change...then make a note and keep it handy.

 

[Rancher Mike]

Mike,

Yes, short Range guys do it all the time.

In winter months I’ve found I need to drop to a slightly lower node to keep guns shooting.

Bart

in long range TARGET shooting do you see a place for using a ballistics app that compensates for temperature variations with multiple data points to get a fps per degree number, or is this more of a tactical / hunting benefit. Mike

 

[BartsBullets]

in long range TARGET shooting do you see a place for using a ballistics app that compensates for temperature variations with multiple data points to get a fps per degree number, or is this more of a tactical / hunting benefit. Mike

Mike,

The ballistics apps are great for predicting point of impact, so for guys who need a first shot hit, they are great. But not what you need to keep your gun in tune.

Bart

 

[dkhunt14]

in long range TARGET shooting do you see a place for using a ballistics app that compensates for temperature variations with multiple data points to get a fps per degree number, or is this more of a tactical / hunting benefit. Mike

It is also not needed for first shot hits in BR. You get sighter shots for that. Matt