https://www.smith-wesson.com/product/mp-15-sport-iii

Free-Float Handguard - Able to mount a multitude of aftermarket accessories.
Mid-length Gas System - Users can expect less felt recoil when shooting.
1:8 Twist 5R Rifled Barrel - 5R rifling profile has consistent contact with the projectile, ensuring a more accurate rifle. The 1:8" twist rate change allows for more variety of ammo to be used.

Priced at $799

Mid-length is easier on both the gun and the shooter. Nice.

After too many years I finally 'pulled the trigger' as this model has the specs I have been waiting for: 1. 1:8 rifling, 2. Full-floating 16" barrel, and 3. full-length gas impingement. Now to flesh it out.

I am 83 and dealing with AMD, mostly in my left (master) eye, and training to aim & shoot right-handed. I'm leaning toward a red/green dot. Any recommendations?
Many thanks, Rich

The SIG Romeo5 line and MSR as well as the Holosun 403/503 are pretty tough to beat for a blend of quality and price. Those budget SIG Romeos are assembled for SIG by Huanic, the parent company of Holosun.

The only downside of them is that the mounts don't have recoil lugs, so I wouldn't consider them duty grade and they may be more likely to lose zero after a hard impact. However, they use the Aimpoint Micro (T/H) footprint, so there are plenty of aftermarket mounts available for reasonable prices.

If you're set on buying American, the SIG Romeo4 line is assembled in the USA (almost every optic is going to use imported lenses and electronics). The 4H models can be found for under $300 if you shop around. They also come with better mounts than the Romeo5 line.

I personally find that green and multi reticles (vs dot only) work better with my astigmatism than red. Green can functionally have better battery life in daylight use since it doesn't have to be as bright as red to be visible for most people. I can also say that blending with foliage is not an issue, at least in the upper Midwest.