K frame .38s first had what was considered to be "modern" heat treatment back in the 1920s, and by report model stamped guns (ca. 1958) had different metal technology such that the factory used to rate all steel K frames as approved for +P .38.

The load you describe does not sound excessive, but if you ask the factory if it is safe in a 70 year old gun with an unknown prior history they will tell you a definite "no". If you see no excessive pressure signs with firing, however, occasional use will probably be perfectly safe, but as noted above caution is a good rule.

If you disclose the powder and charge you are using, one of the handloaders here may be able to quote a pressure and give more information.

__________________
Alan
SWCA LM 2023, SWHF 220