There is quite a bit of research that has to be done to build effective subsonic ammo for high pressure rifle cartridges.
First and fore most will be boolit selection, you will obviously want the heaviest you can get that when loaded will fit in the magazine but not extent TOO far down into the powder column.
Second will be powder selection as you will need a slower Magnum type powder not just the regular powder with a reduced charge weight. There is an effect that can occur when there is too little powder in the case (the name of it escapes me at the moment it may be “Double Boom”). The theory of how a powder works is that the majority of powder is lit by the primer from the rear and forms a molten “slug” that compresses the rest of the powder causing it to ignite almost homogeneously to force the boolit out with the greatest efficiency. When there is too little powder the “slug” can actually "rebound " and the primer becomes the “boolit” obviously fire from the back end of a cartridge is not preferred.
The other factor will be if you are running suppressed as that changes EVERYthing.
Speaking of suppressed and subsonic. The cartridge will still go BANG but being subsonic it will not go “Crack” in a regular barrel, with a suppressor you will still get noise but not nearly as much even if supersonic.
The other issue with subsonic rounds is range and ballistic profile. Big boolits going slow drop like rocks and sometimes depending on the platform are not even viable for 100 yard shooting. Most folks loading subsonic stay at around 1050 fps to allow for the length and breadth of atmospherics as well as the amount of trash that remains in the barrel. Subsonic and suppressed weapons are notoriously filthy.
Subsonic ammo due to the popularity of suppressors has become more main stream but I would have at least 2 - 3 verified recopies of platforms similar to your prior to putting them together. TAKE NOTE This is the ONLY time I will EVER recommend using the hottest load as a starting point and working down.
I’ve been reloading for more than 30 years and have played that game as well as the other end of the spectrum and I would be happy to assist you in your journey and putting together your gear.