Leupold BX-4 Rangefinding Binoculars

Cold and accuracy

nhenry

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Location
Kansas
I developed my 280 Ackley load in 60° weather a month or so ago.

1/2 MOA with 120gr TTSX over IMR 4350 going 3368 fps is what I built. I’ve shot it multiple times and it’s been consistent with that, except for this most recent time.

Over the weekend, I took it to the range in 25° weather and the first shot from the cold bore was right on the money, but subsequent shots spread out to 2” or more.

What in tarnation is up with that?

Can the cold mess up groups that much?

Don’t know if I should be worried or if I should build up a different load in the coming weeks. My hunt’s right at the beginning of December.
 
I developed my 280 Ackley load in 60° weather a month or so ago.

1/2 MOA with 120gr TTSX over IMR 4350 going 3368 fps is what I built. I’ve shot it multiple times and it’s been consistent with that, except for this most recent time.

Over the weekend, I took it to the range in 25° weather and the first shot from the cold bore was right on the money, but subsequent shots spread out to 2” or more.

What in tarnation is up with that?

Can the cold mess up groups that much?

Don’t know if I should be worried or if I should build up a different load in the coming weeks. My hunt’s right at the beginning of December.
Yes it can. Not usually though. Group size doesn’t usually suffer but Point of impact can change. I’ve personally not experienced anything drastic due to cold.
Anything that messes with the harmonics can screw it up. Big difference in velocity can effect harmonics. This is where DOPE (Data on Previous Engagement) comes into play.

Maybe it’s nothing and you weren’t shooting as well in the cold. That’d be easy to overcome.
 
Quite possibly it's the trigger puller.

Lets face it, you may not realize your doing it, but the body reacts to different temperatures also.

My group shooting always opens up in the cold.
you might be correct but I've never had a problem with that before. My main shooting season growing up was in the bare cold. Not saying you're wrong though.

I was told that it may be inconsistent ignition of the primers, so I'm going to do the load exactly the same with CCI 200 instead of Remington 9 1/2
 
Don’t know if I should be worried or if I should build up a different load in the coming weeks. My hunt’s right at the beginning of December.
This depends on intended range if under 350yds you could hunt with it.
In addition to what's already suggested try to look for the changed variables.
Gun barrel/ammo under the heater vent on the way out?
Check barrel float while cold/ hot?
Check all screws in the cold? (aluminum and steel expand at different temps).

Honestly thats not that much of a temp swing maybe its a coincidence.
 
This depends on intended range if under 350yds you could hunt with it.
In addition to what's already suggested try to look for the changed variables.
Gun barrel/ammo under the heater vent on the way out?
Check barrel float while cold/ hot?
Check all screws in the cold? (aluminum and steel expand at different temps).

Honestly thats not that much of a temp swing maybe its a coincidence.
400's the max I will shoot out to, so that's a good point.

- ammo was in my trunk, so no heater
- barrel was still floating, but I wonder if the bedding under the shank was uneven enough to throw shots.
- All metal on the gun is steel, so I doubt it's that. I may have forgot to torque it down to the usual torque specs, though.

I hope it's just a coincidence, because that load shot real well every other time, but I never took it out below 55.
 
Wood steel and aluminum All change at different temperatures. So if they were torque at 70° and you took them out around 30°. That can change everything. Same with ammo. Add it all together
 
I would recheck all your fasteners on your rig. If they are good, I would lean on the shooter. Groups don’t open that big because of 35 degrees. Chances are the ammo wasn’t down to 25 degrees either. We tend to keep ammo in warmer places than ambient temp. It can sit out on the bench for a few min before it gets to ambient temp.
 
I would recheck all your fasteners on your rig. If they are good, I would lean on the shooter. Groups don’t open that big because of 35 degrees. Chances are the ammo wasn’t down to 25 degrees either. We tend to keep ammo in warmer places than ambient temp. It can sit out on the bench for a few min before it gets to ambient temp.
I re-torqued them when I got home. We'll see this weekend.

I will say that the ammo was sitting on the bench for 10 minutes while I got everything set up. Hopefully I'll get it figured out this weekend.
 

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