Good job! Congrats! And yes, cocking tube and barrel look pretty good.
No, tight mag well should not be normal. They aren't on HK's. The easiest and immediate way to predict a tight mag well is to look inside the mag well itself. I have several C93 rifles where there are no rub marks at all and the mags rock in effortlessly and come right out without any drag or hesitation.
Now, just need to find out if anyone has developed a tool or fix for these daang tight mag wells?
One final "parlor trick" for the cocking tube condition is to remove the end cap on the triple tree and see just how concentric your cocking tube is within that triple tree. I have a photo of this from a POF MP5 I purchased. It is perfect! But don't get too upset if yours is not dead center. HK worked it all out but the clone manufacturers still deal with things like warpage when they are welding up the cocking tube, so the barrel may be straight and true, but the coking tube can take a slight bend due to welding and heat warpage. As long as the triple tree was set properly, your sights should work great with all the windage you need to get your strikes on target at distance.
Example of good assembly job. POF MP5.