Sometimes factory made barrels are very rough. Try some running steel wool (4 ought,or 0000) thru the barrel to kick off any burrs or sharp edges. Have you gathered any patches for review? Are you blowing thru your patches, any tears or burn marks?
Shooting a pistol is very different from shooting a rifle. All those muscles that need to hold, balance, squeeze and hold steady that pistol can cause some accuracy problems. How's the trigger pull? Do you start pulling on Sunday and by Tuesday it goes off? Have you bagged the pistol while shooting or is this entirely offhand? Are you using one hand or two hands?
Lastly, what is your powder charge and what grainulation are you using?
15 yards is 45 feet and by my recolection, that is a long distance for a pistol. Pistols are not intended for long distance shooting, unless they have been worked up and designed specifically for target status. When I shoot my modern pistols I am shooting at about 20 feet, perhaps a tad more and I am getting about a 4 inch group. Yet again, I am not the worlds best pistol shot, but I do enjoy shooting them.
You may be jumping the 'gun', so to speak, and you may need to make some obsevations. There may be nothing wrong with the barrel.