I have been piecing together an AR for a while now. For X-mas I got a Spikes Tactical Stripped Upper Receiver which should have M4 feedramps. Upon looking it over it has extremely shallow cut feed ramps. I opened up my bushy for comparison and its feed ramps were rather prominently cut into it. Please let me know for those of you that have spikes uppers.
Personally I would not worry about it unless when you put in your barrel a shelf is formed. M4 feed ramps are much over blown IMO unless you are running FA but they seem to be all the rage right now even for people who will never have a full auto rifle or even aspire to have one. They might not be as deep as some ramps but if they work, there's no problem. I just got a couple from AIM Surplus also but unless there is a problem with feeding when they are built up I am not going to worry about it.
Most of mine look fairly similar if I'm compensating for the angle in my head correctly. Your Bushmaster might have deeper ramps because at one time they dremeled them in instead of buying M4 receivers.
If you aren't going FA don't worry about it.
Wait until you install the barrel. Then post new pic's.