Take a look at this workout....

Alright, i've been arguing with my friend for a while about his workout. i'll give you a little background about him. He weighs about 178, 6'4 and has been working out for 4-5 months. IMO he's past the stage of building a good base, he's gained about 15lbs since he start working out and has 7.5% bf. He works out 4 times a week. His goal is to gain mass, he's currently taking a weight gainer as well, Mammoth 2500.

He does 1 set of each exercise about 12 reps, all exercises are on a machine unless noted differently:

pec fly
chest press
shoulder press
seated row
leg curls
leg extensions
lat pulldown
bicep curls (no machine)
tricep pulldown
leg raises
free weights for back and delts

IMO he should be working out each muscle once a week considering that some overlap like back/bis, chest/tris. From My knowledge, chest needs AT LEAST 72 hours to heal, i'm not to sure about the other muscles, but i doubt 1 day is enough.

Basically, IMO his workout isn't going to get him the results he wants, any outside input would be great, thanks.

Tell your friend to start a one day off one day on shedule, work ONE muscle group per workout, except do chest and tris together and back and bi together. Tell your friend to stop using machines and start using heavy compund movements like benchpress, militarypress, squats, and deadlifts. With all those machines he's using he's only cheating himself.

First 15lb gain in maybe 5 months is very very good. Gains do come early but will slow down sooner or later. If you consider that he only has 80 workouts total assumming he did not miss any on the 4 day week for 5 months. That is a small miniscule number in reality. I think he has done it correctly starting off with machines but I would of added more sets per body part. I would suspect alot of the 15lbs came from some extra calories so make sure he continues. Slowly add the free weights being extreamly cautious about compound lifts such as deads as he risks injury so get a pt too help him.

should he be doing 4-6 reps for his sets?

Personally, I initially favor higher volume training which includes both reps/sets to get the body conditioned with some higher endurance levels, then you can do some periodization after which may include lower reps 3-6 range for some strength.