Your gun may not have been designed for even 2 3/4" loads. 3" Magnums are totally out of the question unless the gun is so stamped.
50 meters or yards is within the range of your gun. If your patterning is poor with #4 shot at that range and closer I'd try a different brand of loads to see if any of them are more agreeable to your Elcee.
You MUST have the chamber length checked if you're not certain about it. I'd be willing to make a bet that it's too short for the loads you're shooting. This will often cause patterns to deform.