Mac is a super nice guy but he is a huge man.
Ya ever see that show where them kaiju creatures come up from the ocean and tore up the cities?
You see how big they were in relation to everything else?
Thats how mac looks around normal sized people
If something is off on your rifle a good gunsmith should be able to find it. You should be able to just look at your gas block inside the rail and see it it's touching.