90gr GMX for deer

[Bassfish1952]

What is your barrel length, again (I forget).
For an 18" barrel and hornady data, 29.5 is MV of 2600 (18"), and  <1000 ke at 250 yds.  1000 ke at ~175 yds for 18" barrel.  For my 18" I can get 2765 for a sierra 90 tgk (with LVR) (2.260 and 30.7 of LVR) but that is a cup/core so a mono likely won't get that fast...  For that bullet's BC you'll need at least 2730 MV to have 1000 ke at 250.

Have you done an OAL seating test to see what OAL you can use with your barrel and that GMX.
Be advised that #400 primers could get pierced in an AR due to thinner thickness of the cup.
#41's or #450's, or 205ARs, are a safer bet.

I have encountered full cases sometimes, at less than "book" max loads, so be on the alert.

Without a chrony... well,  you know.
Suggest using 0.3 gr delta between loads, that's about 1% of case fill and if there is a good node you don't want to miss it with a delta too large. 29.5, 29.8, 30.1, etc.  OK, that delta gives you about 6 load steps to 31.1...

24" barrel and using both Hornady reloading app. and Hornady Ballistic Cal. for info. I am trying to duplicate Hornadays 90gr GMX Bolt Gun data that is in their app. I do have a OAL gauge and I just got 100 primers so if I don't like I'm not out a lot. (they were what my local store had)