How does heat affect the grouping?

[oldracer]

I already know the answer I think but I am looking for some additional info such as how to compensate, how to minimize, etc?

Yesterday at the range it was about 80 degrees more or less and I picked the #1 shooting bench which is very handy but it sits mostly in the sun. So after a bit I noticed that the bullets and cases were pretty warm to the touch and the lube had softened more than I usually see, even in the summer here in San Diego when temps go to 95 or better but I am then in the shade. So the first group of 5 was great, shot the muzzle loader for 5 or 6 shots and then shot the Sharps again and the group of 5 was about double the first group? That is when I noted the cases were hot to the touch so I covered them with a cloth but it was too late. The next two 5 shot groups were also the same so I did not shoot any additional. The lube had not run off but was soft and I was blowing my normal 5 full breaths after each 5 shots with plenty of moisture going into the tube. I don't think the powder expanded unless there was moisture in it and that seems unlikely? The fouling was about the same and after a wet Ballistol patch and a dry one the bore was sparkling clean.

I figure I'll make sure the bullets are well covered in the future, maybe make a small "bullet tent" to cover them or something?? Anyone else seen this?

[RMulhern]

We don't shoot much here during July/August! 95F would be a cold spell!!

[powderburnerr]

kinda sounds like the lube doesnt do its best job when hotter,.when you are done with the blow tube check the muzzle and see if the 5 breaths is making the muzzle wet,most times it takes a few more breaths to soften hotter barrel fouling , When checking the barrel also count down to see how long it takes to grey up again ,this gives you an idea of how long you can wait between shots before your fouling starts reharding.

[NickSS]

I have had the same trouble so when it gets to be warm weather I do two things. First I make stiffer lube and second I keep my ammo in a little osker cooler. This keeps the ammo out of the sun and keeps it cooler. I also use the blow tube more and add breaths as needed. One more thing I do is try to keep the rifle in the shade between relays if possible and I cluean the bore between relays as well. Even with all of this I occationally have had a problem with hard fouling and lose of accuracy.

[montana_charlie]

So the first group of 5 was great, shot the muzzle loader for 5 or 6 shots and then shot the Sharps again and the group of 5 was about double the first group? That is when I noted the cases were hot to the touch so I covered them with a cloth but it was too late. The next two 5 shot groups were also the same so I did not shoot any additional.?
After the first 'big' group, a couple of patches through the barrel would get you to a point to see if the spread was caused by ammunition temperature ... or bore condition.

CM

[oldracer]

Thanks for the replies everyone. I was wiping the bore with a wet Ballistol patch and then a dry one and in looking down the barrel it looked very clean. I would wait a minute or two and then run another dry patch and it would be clean. The cookie at the end of the barrel was nice and concentric and I wiped it off also after each short string. The lube was a little softer than normal but never ran or anything? It is a batch I have from Doug Knoell and has been working pretty darn good so far.

I like the idea of the cooler and I generally put the ammo in J&J plastic cases in an old steel ammo box but I'll use a larger molded plastic one and put some ice in the bottom and leave the ammo to sit inside until ready to shoot 5 or 10 at a time. Maybe put my water bottles in there also? I'll make a small holder for the shells to sit in when I pull them out of the "cooler" just before firing.

[PanaDP]

Perhaps keep your loaded ammunition in an insulated lunchbox in the shade? You could even put a cool (not cold, don't want moisture) bottle of sealed water in there for some additional thermal mass.