if have neither, H110 is a good versatile powder as well, just not as comfy as 4227, but not as harsh as lil gun. I would save the lil gun for hen your a little more experienced with reloading 300blk, ut that's just my opinion, you may well do just fine with it. but it does have a small window of running great, running hot or just running rampant. my accuracy load is Lapua Cuting Edge 90gr .308 bullets, with max capacity of lil' gun, fun round and blows those watermelons to pieces.
but as a good beginner load, any of the 110-125 BLK bullets with H110 will be very simple and have lots of data to look at. Lots of people obsess over 2400 and 1680 for sub-sonics as well. also lots of data exists for the 147gr pulls, generally with H110 as well. Also look for AA#9
blue dot is sometimes ud in sub sonics, not very popular though, but I see a od for 208gr AMAX starting at 7.0 and maxing at 10.0 with accuracy in the 8-9gr range, will it cycle?not sure. really only see Blue Dot being used in sub-sonic "bolt-action" 300's. GOOD LUCK, have fun and be patient.
are you forming your own brass?