3/8 inch boiler plate

[vintage hunter]

The Speer 70gr semi-spitzer you refer to is a good bullet for game up deer sized critters so long as shots are limited to 100 or so yards. It isn't very aerodynamic and looses velocity and energy rapidly. When launched at 2800 fps mv it has slowed down to 1804 fps and 504 ft. lbs. energy at 250 yds.
The Black Hills Mk.262 Mod 0 & Mod 1 77gr OTM round is about as good as it gets IMO for long range shooting with a 5.56 AR, if you can find any. They are capable of making kills out to 700 meters when fired from a barrel 18'' or longer according to the DoD.
SSA offers a load that is said to be very similar in performance to the Mk.262, it supposedly pushes a 77gr Sierra MK at 2750 fps from a 16'' barrel. I have some but have yet to chrono any to see if the claims are true.
The trouble with the 80 and 90 gr match bullets is they are so long that they usually can't be seated deep enough to fit the mag.
At one time there was a Heavy Shot .224 bullet on the market that was the same length as a traditional 55gr .224 bullet but actual weight was 70 gr. Evidently it didn't pan out, I don't see them offered anymore.