Well, for one thing, I have never seen an SAFN-49 with a "dust cover".
Perhaps you mean the Breech-Block Carrier?
First thing you have to learn is the nomenclature of the parts; that way, someone else will understand what you are talking about.
Yes, the FN-49 does take a good, solid wrench to operate when it has a fired casing in the chamber and the Hammer is down.
You mention OIL: are you oiling the ammunition or the Chamber? BOTH are serious no-nos.
If the answer is "no" to both of those, then I would suspect that your Gas is turned off or else is turned far too low. Check the Gas Plug at the forward end of the Gas Tube. It inserts two ways, one for semi-automatic operation, the other way for grenade-launching. For the rifle to operate in the semi-automatic mode, the Gas Plug should exhibit a LINE through it, going from Breech to Muzzle. This tells you that the rifle is set for automatic reloading. If there is no LINE showing, then you are set for grenade-launching and you will have to hand-cycle the rifle every time, which is not a lot of fun.
Loosening the Middle Band and removing the Forward Handguard will give you access to the Gas Regulator. And here you must understand what you are doing, for th FN-49 can be set to give extremely fast operation which brings with it slam-firing; it is actually possible to destroy the rifle if you are not careful.
The FN-49 works on a gas system which bleeds a large amount of gas from the bore, then BLEEDS OFF what it does not need to operate the rifle. That "collar" around the Gas Tube is the Gas Adjustment Collar. It TURNS (you will need a tool), exposing or closing a little HOLE in the top of the Gas Tube. CLOSING the hole makes the rifle use more gas and operate harder; opening the hole bleeds more gas from the system, allowing the rifle to operate in a gentler fashion. The IDEAL setting is with the rifle just bringing the empties out and dumping them onto the bench next to you. It is at THIS position that the rifle will shoot its most ACCURATELY. At that same setting, RECOIL also will be LEAST.
Get a MANUAL for your rifle and read it carefully, several times, until you understand the brute completely. It is a superb rifle, but it does take an educated Operator to get the best out of it. You can start your search for one over at milsurps dot com. They have a HUGE library of manuals for free download.
Likely you haven't run into Gas problems before because you have been using an M-305. The M-305 is a clone of the M-14, which had a self-regulating piston. The SAFN does not have this; it is an earlier design, albeit a very good one.
Good luck.