Not a problem if you have the right stuff. Went to the range today with my 7mm RCBS to fireform 40 new Norma .280 cases. Sometimes you have to grab range time when you can. Temp this afternoon was pushing 90 degrees- could have been worse.

I take along a bag of ice cubes, double bagged in zip locs, and a towel to get wet and put on the barrel.
I fire three rounds, then put the ice on the barrel just foreward of the scope, and a wet towel on the rest of the barrel. After a few minutes, the barrel is cool to the touch. Then fire three more rounds, put the bag and towel back on, to cool while I go downrange to check targets. I'm not really shooting for accuracy, but it is surprising how some of these fireform loads group.
Anyway- in about an hour and a half, I had all 40 cases fireformed, with no barrel heating issues whatsoever.

Beats the heck out of waiting between rounds for a barrel to cool, for sure.

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I'd rather be a free man in my grave, than living as a puppet or a slave....