Yes it applies to all rifles. Bolt of otherwise. The chamber area will get hot and brass is a really good heat transfer metal so it heats up the powder quickly. Almost all powders will exhibit temperature sensitivity about 90 degrees F. The chamber will get to temperatures that can be extreme.
How much? Well for a 308 that has 10 or more rounds fired at about 1 minute spacing without cooldown the round will land anywhere from 0.5 MOA to 1.5 MOA high depending on how long you leave it in the chamber. The rule of thumb I use and most of the people I teach (sucker into coming out to shoot with me) is 15 seconds. After that you should unchamber and get a fresh round.
In as far as actual combat, what my snipers used were M-21s. In rapid fire situations such as occurred one day out at Alligator Lake with a company of the 3rd NVA Rgmt, the range was only 500 yards. I had six snipers lined up on the ridges on both sides of the stream valley from the dam. The NVA tried to cover the 500 yards of ankle high grass with a frontal assault. They broke after covering only 100 yards because the sniper and m-60 fire was so effective. Under those kinds of situation the round is not staying in the chamber for long.
Under more controlled fire situations the sniper will continue to adjust as the barrel gets hotter and the rounds begin to place higher.
Despite what folklore and mythodology will try to say, the M-21 was a great rifle for what we did and the way I liked to run my unit.