Of the ELD-Ms, which will fit in the mag when loaded to proper length and is 1:8 enough spin them? Will the 75gr work, is the 80 an option? Thanks!

The 75 grain ELD-M is marginally stable in the 1:8", and the 80 grain is even less stable than that. The 75 ELD-M should fit, but it's seated very deep in the case. I'd go for the 75 grain BTHP instead. The 80 grain ELD-M in an AR, I think is too long of a bullet anyway. I wouldn't go that route.

The polymer tips add too much length the bullet for the heavier bullets to help fit out of an AR platform.

What Chad said.

I did load some 68 gr BTHP in .223, to AR mag length yesterday, and they look good. I know they shoot very well.

I have not tried the 75's, to see if it is only bearing surface in the neck, and not ogive. Evidently Chad has tried the 75's to AR mag length.

The 73 grain ELD-M and the 75 grain BTHP were the 2 heaviest bullets designed to fit and feed out of an AR-15 (223/5.56 chamber) rifle. The 73 grain ELD-M would work well for your purpose also. The 73 grain ELD-M is 1.046" long and 75 grain ELD-M is 1.121" in length. So you can see the 75 grain ELD-M is a much longer bullet for only 2 grains heavier. They get this length by increasing the ogive to tip length and make a high BC bullet. But the negative is the bullet being seated deep into the case (taking up powder capacity) and the long jump to the rifling from an AR mag. I would run the 73 grain ELD-M or the 75 grain BTHP.

I made some posts showing this in this thread below about the 75 grain A-max. It's the same issue with the 75 ELD-M.

https://texashuntingforum.com/forum...ng-load-data-308-w-150gr-sgk#Post7511183

Sounds like the 73 is it! Thank you, gents, I appreciate your posts.