I think he’s got something else going on. I’ve killed coyotes at 60 degrees and -20 degrees this year with zero poi changeHave a good friend that put an 8" suppressor on his Christensen Ridgeline 300WM last summer. Made the total length 34". Not sure what brand though and I'll try to find out. The gun shot fantastic all summer and fall. This winter though as it's gotten colder, he's missed a few shots on wolves that should have been easy shots. What he's found out in cold weather with this set up is the first shot (250 zero) is 4" high, second shot 2" high, then back dead on shots three and four. After four rounds of four shot groups, it was the same. Cold barrel shot is 4" high. Fairly perplexing and must be how the gasses disperse?