.308 AR Wont Chamber in Cold Weather?

I had a problem last weekend while deer hunting. This is the first year I decided to reload for hunting. I tested several loads and found one that was accurate and took it with me to deer camp. Got out the first morning and saw a good eatin doe within an hour. Took aim, held steady, pulled trigger, click..... Took some serious muscle on the charging handle but cleared the round and chambered another. Didnt see another deer the rest of the morning. Went in for lunch and tried to clear my weapon, same thing. I had to rest the butt of the rifle on the bumper and put both arms into the charging handle and about gave myself a stroke getting the round out. It looked like the neck was what was sticking / rubbing.

I live in Texas and hunt in Minnesota, temp while shooting here was in the high 60's low 70's and temp while hunting was low 40's. Is it just the temp change that caused this? Is there a way to prevent it from happening?

I would really like to know how this happened so I can fix it. Any ideas or information would be really appreciated.

I dont have the rifle with me at the moment so wont be able to test those reloads for a while. But I had zero problems using the same materials and process before hand.

The click was definitely from the bolt not being fully forward. I use very little oil when hunting as it can gum up pretty quick in cold weather, ask me how I know....

The bullet is seated so that it will fit into the magazine and chamber without problems.

Im almost positive it was the way the brass was sized / round was produced, the only problem is I dont know when I will be able to recreate this problem to test for the solution. Is there a way or method to check and measure the problem loads so that I have a reference of what the wrong size / procedure is?

I do use a crimp die, but, very very light pressure is applied when using it. I did over crimp a few rounds when I first used it and have since adjusted it so that I am not forcing the round into the crimp die in any way. But then again I could see how that could affect the chambering.

I have been using the same settings for all my load testing, only changing the seating depth via adjustment on top of die to accomodate different bullets. Do you think that had something to do with it? Its the only thing that I can think of that changed, like I said, I had zero problems while shooting here in TX.

I wont have access to the rifle until friday, its still in MN, but I can try then and see how it comes out. I will bring my caliper with and measure what I can and compare to the factory ammo I used in lieu of my handloads which I had no problems with.

Kernal, thats a good idea, I do have a large upright deep freeze that I could test in, and at the moment its empty so plenty of space for it.

While I should have checked my loads before heading out, I had no problems a week before I left, which is why I am confused that they didnt work

Update

Finally got down to the nitty gritty and checked everything out (in the nice 70 degree weather).

First I loaded a factory federal round to ensure it would chamber, it did

Then I put in the exact same round that wouldnt chamber in the colder weather, chambered just fine although a little extra pull needed to clear the weapon.

So... I thought that the brass might be a little bigger than spec and I was right. Although it was only .002" bigger than the factory federal round it still chambered.

All I can get out of this is that the cold affected the rifle just enough to be a PITA and make me miss an opportunity to get a doe on opening morning.

Any suggestions on how to check loads so that this doesnt happen again?

oops, I should have mentioned that. It is a DPMS LR308 TAC 20 which is chambered for 7.62x51. I also just ordered the RCBS small base die yesterday but didnt think to order the gauge.

Im headed to Cabelas for lunch today so maybe they will have one in stock.