Cold weather and es/sd relation

[DLT]

It’s finally turned off cold where I am in NC. This question might be common knowledge for you guys on here. I haven’t had my Garmin too long and I use it almost every chance I get. When I got it temps I shot in were 75 degrees to let’s say 55 degrees. I always had superb 4.5 sd when shooting in those conditions. Since it’s cooled off to the 30s in the morning and 40s and 50s by afternoon my speed has fell about 30fps which i understand but my es/sd has a little more than doubled. Nothing has changed not the lot of bullets, primers, powder, or reloading process. Is that common to happen when temps drop ? Again I do understand why my velocity has dropped. Thanks men

Forum Boss: DLT was loading with Hodgdon H4350 powder.

 

[HTSmith]

Don't know if its common, but my experience is like yours. Big question is how is it grouping? I usually add powder to get back in the zone. Don't believe the "temperature stable" powder hype. Some powders are better than others but they all change some with temp.

 

[Straightshooter1]

It’s finally turned off cold where I am in NC. This question might be common knowledge for you guys on here. I haven’t had my Garmin too long and I use it almost every chance I get. When I got it temps I shot in were 75 degrees to let’s say 55 degrees. I always had superb 4.5 sd when shooting in those conditions. Since it’s cooled off to the 30s in the morning and 40s and 50s by afternoon my speed has fell about 30fps which i understand but my es/sd has a little more than doubled. Nothing has changed not the lot of bullets, primers, powder, or reloading process. Is that common to happen when temps drop ? Again I do understand why my velocity has dropped. Thanks men

In my extensive .308 data, I don't see that correlation, though the lowest temp is in the low 40's and the temps mostly go from 50's into the 90's. . . and the powder has been AR-Comp. I do think the powder being used can be a factor that way. And I think there's other things at play too, like primers and how a cartridge fits into the chamber due to expansion or contraction before the shot is pulled.

 

[DLT]

Don't know if its common, but my experience is like yours. Big question is how is it grouping? I usually add powder to get back in the zone. Don't believe the "temperature stable" powder hype. Some powders are better than others but they all change some with temp.

Well if I could do my part consistently it would shoot really really good at 100yds. Only difference I can tell from the lower velocity is 1 more click at 500 and 600 distances

 

[DLT]

In my extensive .308 data, I don't see that correlation, though the lowest temp is in the low 40's and the temps mostly go from 50's into the 90's. . . and the powder has been AR-Comp. I do think the powder being used can be a factor that way. And I think there's other things at play too, like primers and how a cartridge fits into the chamber due to expansion or contraction before the shot is pulled.

The powder is a favorite. Good ol H4350.

 

[DLT]

Don't know if its common, but my experience is like yours. Big question is how is it grouping? I usually add powder to get back in the zone. Don't believe the "temperature stable" powder hype. Some powders are better than others but they all change some with temp.

Yes I knew they all do. This is H4350, I should have stated that in original post

 

[Steve Donlon]

What's happening to you is normal, in fact not that bad. I have stopped using IMR 4350 in the winter because it is really effected by the cold weather. It's in the teens then warms up to the 40's most days. I only use RL16 powder and can gain 3 moa at 1000 yards with RL16 and loose that much in the winter with IMR 4350. So it depends on the powder and how much you use.

 

[David Christian]

I would shoot another powder ladder test in the cold weather to see what happens. My suspicion would be that a few more tenths to the upside just might find the sweet spot.

 

[K22]

This from a non-expert but reflects my extensive range and field experience.

Two conditions I have experienced relative to temperature.

1. Significant pressure surge with ball powder in a 22 250 in 90+ degree weather in the field. Never experienced this with any extruded powders.

2. Cold weather (winter) POI lower, about 1/2 to 3/4" comparted to summer POI even with extruded powders. I believe this is due, at least in part, to air density changes, colder being denser. There also could be an effect on powder combustion in cold weather, I don't know.

Whatever the cause, the important issue, at least in my mind, is to always check POI during of change in seasons. For big game, what I observed is insignificant. But for varmints and predator it could be.

 

[Bryan Litz Ballistics]

Seeing ES/SD go up in the cold makes me think about ignition.

Something about the primer/powder combo is happy when they're warm but not when cold.

Have you tried different primers? Some might give you better low temperature performance.

Changing powder could also improve your ES/SD across temperature but that's more of a re-work of your load.

-Bryan

 

[Steve Donlon]

If your are using SRP, that"s for sure. Got to use more powder.

 

[Alex Wheeler]

I have shot in some really cold temps, 15 to 20 below. Never had a problem with accuracy or es. If you do it might be time to bump your ignition up or go to different primer. Your es will probably come down when you adjust your powder charge for the cooler weather.

 

[DLT]

Seeing ES/SD go up in the cold makes me think about ignition.

Something about the primer/powder combo is happy when they're warm but not when cold.

Have you tried different primers? Some might give you better low temperature performance.

Changing powder could also improve your ES/SD across temperature but that's more of a re-work of your load.

-Bryan

I have only recently noticed this since it’s finally got into a continued cold spell. My rifle still shoots good and no noticeable drop at midranges that I shoot at. I am currently using cci 450s but will have to dig around and see what other small primers I have. I believe I have some cci 41s and rem. 7 1/2 put up. I do appreciate you offering advice as well as the others that have

 

[DLT]

If your are using SRP, that"s for sure. Got to use more powder.

I am. 38.5 of H4350 with a cci 450. Case is a 6xc

 

[Steve Donlon]

I am. 38.5 of H4350 with a cci 450. Case is a 6xc

Try enlarging the primer flash hole. I do that with all my SRP brass. But I don't know if that would help with a 6xc but I would try it. Not hard to do. When it's cold out with a SRP you need all the help you can get. You have the right primer.

 

[Steve Donlon]

I just got back from shooting Lapua SRP and Lapua LRP with the exact same load. At 29 degrees I was 4.1 moa at 300 yards with both loads all over the place. By 10:00 O'Clock it was down to 3.1 moa at 43 degrees where it usually is at 40+ degrees, and all other temps. Both loads shot the same tight group with RL16 once it warmed up.

 

[Brad Johnson]

I have shot in some really cold temps, 15 to 20 below. Never had a problem with accuracy or es. If you do it might be time to bump your ignition up or go to different primer. Your es will probably come down when you adjust your powder charge for the cooler weather.

Thanks

 

[Fast14riot]

Its hot more than cold here, I do my load development in the heat, so I notice more of a change when its cold out than really hot. In total I might load up 0.2gr for cold (40°) and down 0.1gr in extreme heat (110°). But it can be enough to take you out of a node.

 

[Doom]

@DLT,
You didn't mention the chronograph but if it is an optical chronograph that may be part of the issue. In winter the sun is coming from a different angle which may be affecting the readings, especially the SD.

I also didn't see the number of shots but if you are talking about a difference in SD of 4.5 to 9 that may not be significant. Also, depending on how the ammunition temperature is changing may be a portion of the change.

 

[DLT]

@DLT,
You didn't mention the chronograph but if it is an optical chronograph that may be part of the issue. In winter the sun is coming from a different angle which may be affecting the readings, especially the SD.

I also didn't see the number of shots but if you are talking about a difference in SD of 4.5 to 9 that may not be significant. Also, depending on how the ammunition temperature is changing may be a portion of the change.

It’s a Garmin. I wish I had bought one when they first hit the market