Temp. affect on the physical size of loaded ammo

[45bpcr]

Had an interesting day at the range today.
I was trying to sneak in one last Sunday shooting before it got to cold to do so.
Winter is coming here in NH and the temp is dropping. I took and bunch of rifles to the range today. Mainly for fun shooting.
Russian stuff, American mil-surp stuff. And my Savage 308F/TR.

We shot away at steel all day from 100 to 500 yds and had a great time. Temps. were right around 35 and a cold north wind was blowing down from the mountians.

We decided to shoot some skeet set up at 500yds. Just to see how many we could break in a row.

1 shot, 1 skeet are the rules.

I had perhaps 100 rnds I made up with Lapua brass and Lapua 185gr Senacars that I loaded back in July or August.
All those rounds shot very well in the summer.
NONE of them would chamber today !

I'm just wondering if the action on the Savage could shrink that much due to cold. Apparently it can.
All that ammo was ladder tested and seating depth was arrived at by being able to just close the bolt on a dummy round.
Then the seating die was adjusted just enogh to allow the bolt to close easy. A very accurate load with no feeding or function problems.

Have any of you folks here ever seen such a thing????

45BPCR

 

[LHSmith]

Since brass has a higher coefficient of thermal expansion than steel by a factor of 2, I don't buy your shrinking action theory. The brass will change it's length (shrink in your case) at a rate twice as fast as the steel in the barreled action. More likely the bullet pushed out of the case due to a compressed load that had light neck tension....I re-seat my preloads immediately prior to each match to avoid this.

 

[Kenny474]

Have you tried the ammo again at home where it's warm to see if they now chamber?

I too have a hard time believing the action shrunk so much your ammo won't fit. If it was that tight to start, I think you would have constant issues anyway.

I would have put the rifle in the truck with the heat on to see if that helped, but I still can't see that being an issue. I have hunted in severe cold with no ammo chambering issues, and that's with the ammo close to my body and warm, and my rifle at about 5 degrees F.

 

[LHSmith]

Didn't do any calculations but with such a small temp. change, the amount of dimensional change would be very small, to the point that it would be difficult to measure. I would bet you would not have any chambering difficulties even if the rifle was at 0' F. and the ammo at 100' F.