300AAC Blk 150gr Cast/Coated Flat Nosed Seating Depth Question

Disclaimer - Im just trying to reload my first loads

I just made some .223 62gr fmj ladder loads and loaded them to the seating depth recommended in the book which is basically as long as they can be to still fit in the magazine and in the go nogo gauge. Im now trying to load .300AAC Blackout with some cast bullets I cast, coated, and sized to .310. These are flat nosed so the OAL is obviously going to be much shorter. I dont have an ogive thing to measure from on the calipers but I do have a saami spec go/nogo gauge. I seated a bullet to what fits in the go/nogo gauge and it was 1.7835. I then loaded one really long and chambered it from a pmag into my .300AAC AR pistol and made sure the bolt closed completely. I then measured that round and it was 1.8520. My question is what length should my OAL be? If you aren't comfortable giving me a number can you help me find a place to find the theory behind the solution? My thoughts are to chamber a couple then seat them slightly deeper than what that yields me. This is the only gun these will be shot from.

More info:
8.5" AR 300AAC pistol
H110 Powder
150gr cast/hi-tek coated FN projectile
Use: Range plinking only to 150 yards max
Manual says: 14.6 - 17.2 (never exceed)
My ladder was going to be: 14.8 - 16.6

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