15 yds is not a real test of a guns accuracy. Real accuracy begins at 50 yds & goes out beyond that. (Think hunters, silhouette shooters, etc)
Many guns can shoot very good at close ranges,, but not at distance.
Have you slugged the barrel & got a REAL reading of the barrel dimensions? If so, how does it compare the the throats? Have you measured the throats with pin gauges?
With all that,, if YOU are happy,, and YOU are aren't experiencing any issues,, leave it alone.
BUT,,, having a gun that has uniform chambers,, of a proper dimension, (usually .4525 for cast bullets,) that mates with the barrel dimensions, will be a better all around gun. And if you get to shooting at distance,, or a different load,, then you may well choose to have the easy & inexpensive work done to open up those chambers.
We have 2 FINE gentlemen around here that can help with this;
Fermin Garza also known as; "2dogs"
And "DougGuy"
My shooter OM 45's have all had their throats uniformed to a proper .4525.