Cold bore shooting at cold temps ?

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06shooter

New member
In October at 70*, was getting .75" groups with my 3006 using 56.0 gr of Imr 4350 ,cci 200 , new nosler brass and 165 gr BT @ 100 yards.
I shot the same load @38 * shooting a cold bore for each and every round and this put me over an inch in group size.

I know this is no big deal for deer hunting , but how do I close the group ?
Since pressures are lower in cold weather , do I add more powder , or use a mag primer to make up the difference?

I know some might say , go test it and I will, but what are your experiences ?
 
I the load does not suit you I would recommend you start with what you have and work up another load for cold weather.
 
A difference of a 1/4" at 100 yards... my first thought is "How many shots are your groups?".

A 3, 5, even 10 shot group on 2 separate occasions can easily be 3/4" one time and 1" the next, no weather variables needed.
 
You're over thinking this. The difference in accuracy is insignificant and could be because of many variables other than the cold.

MOST powder will change 1-2 fps for every degree temps change. The difference between 70 and 38 is only 32 degrees. You lost no more than about 30-60 fps. Not a problem, you'd need 75-100 degree temperature change for it to be a concern. Even if you did add more powder or change primers to get that 60 fps back at 38 degrees, you will be 60 fps faster again at 70 degrees and possibly over pressure at 90-100 degrees.

If it is a concern to you, then you could change to a more temperature stable powder. H4350 would be very similar and it only changes about .5 fps for each degree. No more than about 15 fps in this case.

The powders may have the same number, but load data is not interchangeable. Close in my experience, but not exactly the same. I use both powders and usually find the best loads are within 1-2 grains of each other.
 
Thanks Brian, yes just 3 shot groups.
What you said about a 1/4 difference and weather variables is good to know.

There was one 3 shot group that went in the same hole , but I shot this back to back ( no cold bore ) maybe a fluke !
 
As much as we'd like to believe otherwise (and this coming from a guy who almost always shoots 3 shot groups), basically all 3 shot groups are a fluke. They're about 1/10th as many shots as you need to truly be confident in your group sizes... even then depending on if you want 90% confidence or 95% or...


If you want a headache, read this post, on another forum but written by our own UncleNick.
 
Could the way you were dressed make a difference? At 70 I would be in shirt sleeves but at 38 I would have a winter coat on.
 
Cold weather the air is dense, will change POI lower. Most of the time whether foul or cold bore shots I feel is from oil left in the barrel. Always run dry patches 3 through the barrel before shooting and shot a 5 shot group, see how they group.
 
06shooter,

A couple of summers ago, I saw a shooting show which covered how a warm/hot barrel vs. a cold barrel will affect your point of impact. I'm sorry, but I don't recall the show or the outcome. On the show was an instructor with the Army's sniper school. He demonstrated the difference in POI with just a couple of shots. This may be part of your problem.
 
Thanks cw308, I dry patched it and shot factory 165 gr accubonds ( 6 fouling shots ) before I went to hand loads.

My loads grouped better than factory. at 38*
At 70* the factory ammo was tight.

In October, I started at the start charge , worked up in .5 gr increments, I found
53.0 , 55.0 , 56 and 57 were all sub moa 3 shot groups.

I let the barrel cool between 3 shot groups.

I guess I'm taken it too easy on my rifle LOL !
 
06, you should baby it. That's why it shoots so good. I'm a benchrest shooter, I have a temperature strip on my barrel from McMaster-carr if it gets to 113 I let it cool.
 
All powders are temperature sensitive to some degree or another some more than others. Hunting loads tuned in July do not work as well in January. We forget that ammo sitting in the sun on a bench in July is hotter than those in the gun during hunting season. To help compensate for the differences it is a good habit to store your hunting ammo in a inside pocket of your jacket up against your body heat of 98.9 degrees. While you may not want to load your rifle after you spot a deer, you could rotate the rounds in your rifle every half hour or so until you actually need use them.

While not the cure all of temperature changes, it should go a long way to help you keep the sub MOA results of your summer tests. While barrel temperature will effect how the gun works, it is not as effective in changing the temp of the powder, unless you are shooting semi-auto like in a AR-15 fully auto. So cold barrel shots in July and January should be similar, maybe not exact, but close enough. You need to keep your ammo warm during cold weather. Or develop cold weather loads.

Good luck and good hunting and stay safe.
Jim
 
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OK I noticed that you mentioned that every shot at 38* was a cold bore. Was this the same for the group shot at 70*? I ask because I've done a ton of experimenting with cold bore shooting. My current rifle has amazing consistency. 3 round groups are good for .6 moa groups, with less than a .1 moa deviation through probably the last 100 groups. 5 round groups will come in at about .75 moa, same deviation.(better groups when the barrel was new... Such is life).

I have found that my groups don't change much when I start with a cold bore and no fouling shot (almost an immeasurable difference with 3 round group, probably .8 moa 5 round group). I have tried several times however, to shoot groups with a completely cold bore each shot. MUCH greater difference. The 3 round groups I've tried neared 1 moa (never over), while all 5 shot groups but one were over 1 moa. There is a much greater deviation too. One group may be .3 moa greater than the other

I have noticed my poi does not change significantly with a cold bore, however. Out to 300 yards (furthest I've don't any cold bore trsting) I can't see a poi change that is outside of 3". Which almost matches the expected accuracy of the rifle so there's no need to try and adjust.
 
38F isn't that cold. Kinda balmy in some places. snicker.
IMR4350 is known to be temperature sensitive and using a magnum primer isn't going to change that. Changing primers will require working up the load again too.
"...just 3 shot groups..." Your rifle hold more? A mag load or 5 out of a cold barrel is better for hunting loads.
 
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