Effects of lower temps on accuracy?????

[oldracer]

I finally got out to the range today after a month of not having the truck, being sick and days of rain and took one of my Sharps! It generally shoots pretty well with 5 shots touching at 100 yards on cross sticks. My loads are: fire formed cases with slightly belled mouth, 68gn FFG Goex, milk carton wad and news wad on top of that, 500 gn Lee pointed bullet at 20-1 lead with Doug Knoell pan applied lube. The bullets are finger seated on a compressed load (w/ compression die) so that the bullet is 0.002 off the lands, no crimp. I seat the case in the breach the last 1/8 inch with a cartridge seater and get no blow by. I blow 3 breaths after each shot when cool, 5 when hot.

The temp at the range was 48 degrees with 60% humidity and the loaded rounds were at ambient temps and the lube was nice and soft. So I noted the first shots (3) were about 3 inches higher so I lowered the rear sight a mark and then they were on level but spreading slightly. I noted the barrel was not getting any heat except right at the breach end. I tried wiping between each shot and there was no difference?

So I am thinking of lowering the powder charge to 66gn possibly and see if that works better in the cold. What do you guys do for lower temps and I KNOW 50 degrees we have in San Diego is way higher than many have but this is the first time I have seen this?

[John Boy]

What do you guys do for lower temps
* The bullet will drop when the temperature goes down. Just adjust your sight setting
* Colder bore shrinks, more friction, denser air for the bullet to pass through, minor drop in point of impact. But at ranges under 300yd, you probably won't notice a difference

[Boz330]

My scores usually go up in the winter. In fact the worse the weather the better I seem to shoot. I think that the fouling doesn't get as hard because of the barrel heat during the winter. Sometimes I wish the barrel was a little warmer so I could warm my hands on it. In the summer you need a rag to hold it to clean after a sting of fire. I don't know if you can blow tube enough for that kind of heat.

Bob

[Gunlaker]

I usually shoot better in the summer. The main issues I find in winter are:
Worse light.
Heavier clothing makes it harder to be consistent in technique.
Cold hands make for less control.

Chris.

[montana_charlie]

The temp at the range was 48 degrees with 60% humidity and the loaded rounds were at ambient temps and the lube was nice and soft. So I noted the first shots (3) were about 3 inches higher so I lowered the rear sight a mark and then they were on level but spreading slightly.
When I see 'lower temps' in your thread title, I get a different thought pattern than you probably do.

So, I'll have to put this qualifier in first ... If 48 degrees is far enough below your normal temperature to make a difference ... your powder may not be burning as efficiently as when it's warmer.
In that case, muzzle velocity is slower and your muzzle is in a higher part of the recoil arc when the bullet gets there.
Therefore, it hits higher on the target.

If true, dropping the powder charge should make the problem MORE noticeable.

[oldracer]

Making the change more noticeable with a single change was my intent. If accuracy gets worse then I would go up a bit. Since the range is in low mountains about 18 miles from the ocean the spring/fall temps run around 78 to 80 and summer can get to 95. The higher temps seem to not bother accuracy that much and I was considering bringing out the Leadsled to see if it was due to me just being cold.

Yeah I know 48 is far from cold in many parts of the country.......

[montana_charlie]

the spring/fall temps run around 78 to 80 and summer can get to 95. The higher temps seem to not bother accuracy that much and I was considering bringing out the Leadsled to see if it was due to me just being cold.
Now I understand.
Considering your normal temps, I don't see 48 degrees as low enough to make a noticeable change in powder burn.
But, when it come to how our bodies react to 48 as opposed to 70 ... after we become 'high mileage types' ... that IS something to consider.

For me, 48 degrees is just high enough to tempt me to set up the benchrest and put up a target, if the sun's out and the wind is down some.

CM