The use of fast low density pistol powders is almost universal in its application. It is really hard to get away from it.

As seen from the above comments Unique, Bullseye and W231 are some of the most common powders used in .38 special loads.

But there are some fast rifle powders designed for use in small calibre rounds like the various .22’s and 6mm’s that make fantastic slow pistol powders. My old favourite was Hodgson’s H4227. 10 - 11 gns in a .38 case under a 148 - 158 gn lead bullet made a great +P load. It is impossible to double charge these powders without overfilling the case.

I have no experience with IMR 4227 but did load with the Hodgson replacement which here is sold as ADI/Mulwex AR2208, H4227 with a special coating for the Australian military .223/5.56 round to reduce burning temperature (ADI made both AR2208 and H4227 for Hodgdon for many years until corporate budgets saw the Hodgdon powder cease production).

Trail Boss seems to be the bulky “go,to” powder these days for many pistol calibers but I have no experience of it. And while others don’t seem to like it too much I have had outstanding success with Tightgroup in so many calibers from 9mm up to .45 ACP. Yes it is far from clean burning but I recently had some accuracy issues with a 9mm with some particular ammunition requirements and in the end a maximum published load with TG proved to find the “majic spot”.

Just be careful. I recently had the first really bad experiemce with handloading in over 25 years. It was very unpleasant and I was lucky

One last thing, why the +P reuirment? Mid - top range velocity standard pressure rounds are more accurate.