Perhaps you can reference Laser Cast load data by Oregon Trail Bullet Company (Page 78).
And if you are looking for lighter target load that won't lead the barrel, you could even reference 170/180 gr loads for initial powder work up to identify charge weight that will reliably cycle the slide and extract/eject spent cases then go up from there -
https://oregontrailbullets.com/xcart/images/filemanager/uploads/otbc-load-manual.pdf
"Caution: These loads are intended for use in pistols with fully supported chambers ONLY!"
- 40S&W 155 gr Lead RN SWC Universal OAL 1.135" Start 5.1 gr (1066 fps) - Max 5.6 gr (1136 fps)*
- 40S&W 170 gr Lead SWC Universal OAL 1.135" Start 4.6 gr (1000 fps) - Max 5.0 gr (1065 fps)*
*FYI, Laser Cast load data carries the following caution on page 80 - "Maximum loads for unsupported chamber service pistols"
- 40S&W 155 gr Lead RN SWC Universal OAL 1.135" Never Exceed 5.3 gr (1097 fps)
- 40S&W 170 gr Lead SWC Universal OAL 1.135" Never Exceed 4.6 gr (1013 fps)