Hey Chris,
I got a question for you. What month of your training did you complete your first muscle up? I've been working out for about 3 to 4 months and it's still a struggle for me.
If I am correct, Chris got it on his 4th month. Dude, don't worry, 3-4 months is not a lot, as Chris says "Everyone progresses differently", some might get it in 3 weeks, some in a year. What matters is that you don't give up and make sure you're progressing whether it's slow it doesn't matter. Four months really isn't that much of a time, keep going you'll get it!
Daniel Malo