Uncle.45,
I have merged your two threads as they are really connected and you can see already the from the above comment that having it separate disconnected the discussion from fact you are trying to get a light load to work.
A few thoughts on both topics:
One is that the RNFP shape is a CAS load shape and has a shorter bearing surface than the 185 grain SWC's we used to shoot in matches. This means it doesn't seat as deeply, leaving more room under the bullet and that extra volume will lower the pressure, make ignition a little slower and on both accounts will contribute to a little more fouling being present. I've always used a shape
more like the 185 grain SWC on the Dardas site. He gives TFL members a 5% discount, IIRC, so it might be one to try.
Missouri Bullets has the same shape listed at .45 Button and has a coated version if you prefer that, but no discount.
Any time a spherical powder seems to fail to burn well, try a magnum primer. The larger shower of sparks helps them get burning. CCI reformulated their magnum primers in 1989 specifically to improve the ignition of the St. Marks ball powder formulations, of which OBP231 (sold in canister grade as HP38 and 231) is one.
Another way to improve start pressure is to get the bullet into contact with the lands before the case mouth reaches the end of the chamber. This is called headspacing on the bullet. It increases accuracy both by improving ignition consistency and by aligning the bullet with the bore, and it also reduces leading because of that better alignment. The main limitation is that some bullets seated out that far no longer feed from the magazine properly. Also, seating out that far might leave your particular bullet short of enough seating depth to feed without tipping the bullet. You'd have to try it out to see. It is done as shown third from the left, below. You use the barrel as a gauge to set your seating depth so a round dropped into the chamber has its head face flush with the barrel extension (hood).
Beyond that, while the gun functions well with full power ammunition, it may need some slicking up to work with lighter loads. Since I can't inspect it, I can't say, but a gunsmith might recommend a reliability package in which he may radius and polish the feed ramp, break corners on the locking lugs, and so on to improve overall feed and function, and possibly lap it lightly in places. Stainless steels can be grabby compared to plain and carbon steels. This is the reason early stainless guns were often faulted for galling. The alloys now used are generally better, but not as easily made slick at plain and carbon steels.
That said, there are lubricants you can get that are permanent or semi-permanent that may help. One of these could be applied to barrel locking lugs and link lugs, to the slide and the disconnector, to the frame rails, to the firing pin stop, etc. These parts can affect either unlocking or locking. Sprinco Plate+ Silver has worked well for me. Shooter's Solutions MolyFusion makes an even more obvious difference, turning the metal surface almost waxy feeling, but it has a tiny thickness to it (half a thousandth, IIRC) and is more expensive to buy into, so I think it would be my second choice for tight fitting parts.
