We've been shooting at mid distance (400 - 600 yrd.) with .300 Win Mags lately. A cool bore with just a few shots, holds a good grouping. As the pace picks up and the barrel heats, the point of impact seems to start dropping considerably. The temps we're in are between 25 - 30 deg. F. I've used the search, and haven't been able to address this problem directly. I'm hoping I can avail myself of the very considerable experience here. Thanks.
Cold weather shooting
- Thread starter Newtrick
- Start date
Re: Cold weather shooting
Are you sure it's not due to the fact that your AMMO is cooling down from being outside instead of a warm car? Some powders are very temp sensitive and will cause this.Try keeping the ammo warm OR at least the same temp from beginning of shoot to end.....
Are you sure it's not due to the fact that your AMMO is cooling down from being outside instead of a warm car? Some powders are very temp sensitive and will cause this.Try keeping the ammo warm OR at least the same temp from beginning of shoot to end.....
Re: Cold weather shooting
Great thought. I'll keep that in mind. The phenomenon happens during one 5 round mag. 90 to 120 seconds. In that period of time the barrel heats fairly quickly. I'll be more sensitive to the storage and use temp though. Thanks.
Great thought. I'll keep that in mind. The phenomenon happens during one 5 round mag. 90 to 120 seconds. In that period of time the barrel heats fairly quickly. I'll be more sensitive to the storage and use temp though. Thanks.
Re: Cold weather shooting
Keep in mind temps effect external ballistics as well, I believe the rule of thumb is approx 1" for every 10 degrees in temp change from your zero at 100. 1" higher for 10 degrees warmer and 1" lower for every 10 degrees cooler due to the thickness of the air. Just some food for thought...
Keep in mind temps effect external ballistics as well, I believe the rule of thumb is approx 1" for every 10 degrees in temp change from your zero at 100. 1" higher for 10 degrees warmer and 1" lower for every 10 degrees cooler due to the thickness of the air. Just some food for thought...
Re: Cold weather shooting
Rules of thumb are constructed from a set of specific conditions for a specific load in a specific rifle.
It would be wiser to ignore such rules, and use a ballistics program. If one doesn't have any other access to one, this one is online, free, and very good:
JBM Ballistics
And one must take into account the effect of temperature of muzzle velocity.
Rules of thumb are constructed from a set of specific conditions for a specific load in a specific rifle.
It would be wiser to ignore such rules, and use a ballistics program. If one doesn't have any other access to one, this one is online, free, and very good:
JBM Ballistics
And one must take into account the effect of temperature of muzzle velocity.
Re: Cold weather shooting
If you're using an Alliant or IMR powder, that is why your dope is changing as the ammunition cools off. They are very temperature sensitive. Try using Hogdon extreme powders.
If you're using an Alliant or IMR powder, that is why your dope is changing as the ammunition cools off. They are very temperature sensitive. Try using Hogdon extreme powders.
Re: Cold weather shooting
The temperature and how the ammo is being stored etc...is a variable.
Usually as temperature drops and the ammo is colder etc...you loose a little velocity. This will change the impact you see on the target.
There are powders that are more sensitive to temperature change than others and will cause more erratic groups on your target.
In my opinion though all powders and loads the temperature they are being shot in will have an impact on velocity.
My .284win. at 80 degrees vs. shooting it at 21 degrees F (I've actually got chronograph data and keep the records) if memory serves me right the velocity is like 40-50fps. slower at 21 degrees and this is with a temperature stable powder. The gun had no change in groups sizes etc...but the slower velocity did show a difference on elevation on the target.
Another problem you might be having is the barrel itself. A barrel that has a bad bow in it or a lot of stress can change/walk the groups on paper as the barrel heats up during shooting etc...When the barrel cools down and you start shooting again you might see it start printing in the spot it originally did and as it heats up the groups walk or string etc...
My hunting rifles when I load ammo or zero the scope etc...I test the gun as close as the conditions that the gun is going to be shot in. What I mean is if I normally hunt with the rifle and the average temperature is say around 20 degrees than I zero the rifle with the ammo I'm going to use and try and shoot it in those conditions so I'm not getting no surprises. I don't load ammo for the gun and shoot it at the range to zero or check the zero on the rifle if it's 85 degrees out. On a new rifle I will and once it's set up that's fine but as hunting season gets close I will take the gun out in the types of conditions I will be using it in and see if there was any change in zero etc...
It comes down to you need to know your gun ammo etc...and what it's doing/how it will perform.
Later, Frank
Bartlein Barrels
The temperature and how the ammo is being stored etc...is a variable.
Usually as temperature drops and the ammo is colder etc...you loose a little velocity. This will change the impact you see on the target.
There are powders that are more sensitive to temperature change than others and will cause more erratic groups on your target.
In my opinion though all powders and loads the temperature they are being shot in will have an impact on velocity.
My .284win. at 80 degrees vs. shooting it at 21 degrees F (I've actually got chronograph data and keep the records) if memory serves me right the velocity is like 40-50fps. slower at 21 degrees and this is with a temperature stable powder. The gun had no change in groups sizes etc...but the slower velocity did show a difference on elevation on the target.
Another problem you might be having is the barrel itself. A barrel that has a bad bow in it or a lot of stress can change/walk the groups on paper as the barrel heats up during shooting etc...When the barrel cools down and you start shooting again you might see it start printing in the spot it originally did and as it heats up the groups walk or string etc...
My hunting rifles when I load ammo or zero the scope etc...I test the gun as close as the conditions that the gun is going to be shot in. What I mean is if I normally hunt with the rifle and the average temperature is say around 20 degrees than I zero the rifle with the ammo I'm going to use and try and shoot it in those conditions so I'm not getting no surprises. I don't load ammo for the gun and shoot it at the range to zero or check the zero on the rifle if it's 85 degrees out. On a new rifle I will and once it's set up that's fine but as hunting season gets close I will take the gun out in the types of conditions I will be using it in and see if there was any change in zero etc...
It comes down to you need to know your gun ammo etc...and what it's doing/how it will perform.
Later, Frank
Bartlein Barrels
