#4mk1 Magazine issues

I have a newly required number 4 mk 1 that is in excellent condition and shows little wear. The bolt matches the receiver. I shot it for the first time today, using both an original factory mag and an aftermarket mag. The ammo was 174 grain Privi. I had the same problem with both mags. When closing the Bolt to chamber a round, the top round would not budge out of the magazine. This did not happen on every round, but was consistent. Each magazine looked the same as far as the forward ears that hold the front of the round down in the magazine. It appears as though the top round in the magazine wasn’t pitched high enough to easily slide up the feed ramp. Towards the end of the shooting day, I was having better luck as I used more muscle to close the bolt. I have another Number 4 Mark 1 that is well used, and I can’t recall having that problem with it. Thoughts?

Have you tried those mags in your well used No.4 as if they cycle fine in that then its not the feed lips that are the issue but something else I always have 10 dummy rounds made up for checking cycling and mag springs.
As if its not the lips it's something else, also I always buff up my feed ramp with a buffing wheel on a dremel just helps the tip slide a bit easier I'm sure more experienced ppl will be along shortly, be careful adjusting the lips they are like gossamer when being bent and snap easily I have heard.

Mags don't fit right from "The box". They have to be fitted and tweaked. The lips might need a touch up or down and the spine might need an adjustment so the mag fits properly. They are soft material and not meant to be changed like an FN or a US M14. They are meant to be fitted and the charger loaded.