At one point, we moved from close shooting (under 100 yards) to a spot on the farm that had a clearing that went on for a bit more than 600 yards. I had my recon rifle (RECCE), and my cousin had a mini-14 with him. The mini-14 had a 3-9x scope, and my RECCE was outfitted with a TA31F ACOG. The RECCE rifle also had a bipod.
We took a moment to guess the range, and both came to the agreement of 600 yards. We took another moment to find a good spot, and once we had it, I set up the rifle. I shot first with 55-grain Federal AE. This stuff mimics M193 very closely, and I've found it to be extremely accurate for what it is.
Note: My cousin's friend took a rangefinder to the same spot and determined the distance was 614 yards.
The target was 18" square. I fired on it and recorded hit after hit. My cousin was spotting with his mini-14. 10 shots later, I let my cousin have a go with the recon rifle. He scored 9/10 hits, and was just high on the other shot.
We "walked" the mini-14 onto the target (plain reticle was set for 100 yards). We just used holdover, but found a target "above" the formal target that when in the crosshairs, would allow the bullet to strike the regular target. Once we had the holdover correct, we fired 10 rounds - five apiece - at the target. We hit three times (all three by me).
Immediately, the heavy barrel RECCE with the free float rail (thanks, LaRue!) stood out in a good way over the mini-14. To be fair, these sorts of accuracy issues with the mini-14 platform are well documented, and we expected these results. Thankfully, the dirt around our target would kick up as an indicator when we would miss.
Then we changed ammo in the RECCE rifle. First, we tried a Winchester Ranger 69-grain ammo. I tried it first, and put all three rounds on the target using the "6" hash mark. My cousin replicated the feat. My conclusion is that if the Winchester Ranger ammo's drop is different than the 55-gr. Federal AE, then it is within minute of angle (approximately 6" at 600 yards).
Next, we tried some 75-grain Prvi match ammo. Given the results of the previous ammo, I elected to fire three rounds using the "6" hash mark again. Again, I scored three hits. Again, my cousin duplicated the results. Again, my conclusion is that if the drop is different, it is still within minute of angle at 600 yards.
Trijicon says on their website:
The real issue is not the bullet weight or barrel length, but muzzle velocity, ballistic coefficient, and the distance from height above bore. The difference in trajectory from bullet to bullet or barrel to barrel is usually less than the MOA thickness of the stadia lines.
I'd say most M193 / M855 clone ammo, along with most quality match ammo or higher velocity hunting Because of this, it was almost like cheating... knowing exactly where the bullets would strike without ever having shot them before from that platform at that distance.