Your magazine will most likely determine the OAL you need. I load 185 grain JHP bullets from Montana Gold and use between 1.200 and 1.220 OAL. Put in 5.2 grains of WST and I'm good. Seating bullets deeper in the case will raise pressures. If you don't already have a good load to use, start at the low end and work up slowly. I don't normally load more than 10 rounds for my starting load then 10 more with .1 grains of additional powder. I do this until I get up to the upper mid range. I hate pulling bullets so I don't make very many of a new load. Once I get what I'm looking for I might try some that have no more than .2 grains more powder so long as I'm in a safe range. High speeds generally gives me worse accuracy. I test in 5 round groups. 10 rounds will give me two different groups of a given load to test. I generally get 3 or 4 loads that will work pretty good and I take the one in the middle. An example is 5.1, 5.2 and 5.3 grains work well. I load with 5.2 grains of powder.
When checking the OAL in your magazine make sure you fill it to capacity. The first few might work but when too long they might not work when you fill it up.