Good for you Rehat, sounds like your doing well. Yes, work up 5 grain increments with the.015's then work up 5 grain increments with the .018's. Give the gun the benefit of a clean bore during each change and you will see the difference, you'll find it. it ain't gonna happen in one day.
Now your biggest problem isn't that big, it's very common and many times overlooked by even the pro's!
Biggest problem was ignition. Used CCI #11 Magnum caps and sometimes the cap would not fire on the first try.
That darn T/C coil spring lock! Lyman uses the same thing, and it's a part called the, "fly detent".
The fly detent is in place to allow the lock sear to fall or skip past the half-cock safety cam when the set trigger is used. Single trigger, does not alleviate the fly. The lock is still the same.
Next thyme ya clean your gun, after the barrel is out, take the lock out. On the inside of that lock is a plate that has 3 screws, if any of those 3 screws are even the tiniest bit loose, or those little parts in there ain't been cleaned or lubed in a while, them lock parts will STOP the hammer just short of the nipple drop! because that "fly" will seeze or tip just that little bit.
If the hammer fall's,,the cap will snap. if the cap snaps, and there is no BOOM? then we have a different trouble,