i know for a fact that they swell
i live in kansas and right now we have had like 3 cosectutive weeks of 100+ temps and a heat index of 110 and like 90 percent humidity or somethin like that (im not a weather man) and the moisture in the air will soak into your gun's bolt and make it swell..the reason i know is that when you have it at room temp (75 degrees) the bolt can bounce around in there a little and after the day of playing in the heat i could hardly pull the bolt out!
i know this didnt make much since..(me just trying to talk like i know what im talking about)..
have a nice day
-"only the dead know the end of war"- plato
-"cowards die many times before their deaths"-sacratese
-"gun control is when you shoot with both hands"-
-"when in doubt empty the clip"-