[FFmpeg-user] Question about file size changes

[David Shuman]

I have a video recorder that outputs files with an .mts suffix.  mediainfo identifies these files as BDAV more commonly .m2ts files  I attempt to copy these files with the following commands

ffmpeg           -i      "D:\Dave\Videos\010-raw\mts\Charge-05082019-2255.mts" -c copy                          "D:\Dave\Videos\020-fix\mts\Charge-05082019-2255.mts"                2>&1  | wtee    "D:\Dave\Videos\log\mts\ffFIX-Charge-05082019-2255.txt"
I renamed the file to have a .m2ts suffix and tried again
ffmpeg           -i      "D:\Dave\Videos\010-raw\m2ts\Charge-05082019-2255.m2ts" -c copy                          "D:\Dave\Videos\020-fix\m2ts\Charge-05082019-2255.m2ts"                2>&1  | wtee    "D:\Dave\Videos\log\m2ts\ffFIX-Charge-05082019-2255.txt"
The resulting output files according to mediainfo have had their video bit rates increased     The original is 1778 kb/s regardless of file suffix, the .mts copy is 1817 kb/s and the .m2ts copy is 1870 kb/s.  

Why do the copies have higher video bit rates?  Nothing else significant appears to have changed  the .mts claims format is mpeg-ts  on the output, all other formats both input and the .m2ts output claim to be BDAV.
Is there a way I can keep the bit rate the same so the copy matches the original except for corrections made during the copy for missing franes, etc?