Its a true story. Good friend was there and he confirmed. I can't imagine anything else that caused it to keyhole, tho 1 foot does seem tight quarters.
Testing the Vegetation Deflection of 5.56
I've done field-expedient testing with 5.56 in heavily saturated, wet, dense vegetation in between the shooter and IPSC cardboard targets at 25-50m. Shooter couldn't even see the target, but he made sure he was aligned by popping his head up, then getting back behind the gun in the prone.
Point of Impact was Point of Aim, no key holes. We kept testing it thinking it was a series of flukes. Nope. Nothing but consistent clean holes in the target. We did this when the conversation of "twigs deflecting 5.56" arose. After 15 rounds, we got bored with it and went back to training.
Penetration of M855 Through Trees
I've also seen what M855 does in the jungle in Central America. It cut through trees I thought were cover, the largest base trees I have ever seen outside of the Redwood forest.
Real-world Wound Ballistics
Then there's the "mousy" wound ballistics I have personally witnessed on human beings with M855 over the years. Everybody has seen the enhanced Zapruder film, right? That is
almost as bad as what M855 did to a guy I saw shot in the exact same place, but it canoed his head cleanly, like a large pie slice missing. Everyone that I've seen that caught 5.56 to the arms or legs had multiple fractures to the bones, usually avulsive tissue separation, massive hemorrhaging, and pretty gruesome injuries, even if the projectiles skipped off SAAPI plates after going through a wall.
There is a big difference between 5.56 M193, M855, and certain civilian FMJ's however, in that the 2 legacy 5.56 loads have thin jackets, cannelures, and run fast, whereas a lot of civvy ammo I have used has thick copper jackets, no cannelure, and slower speeds. Lot-to-lot variations in the military ammo can also see slight jacket thickness variation, which affects the fragmentation threshold range.
If someone said they were going to shoot me with a 7.62 NATO FMJ in the chest, or a 5.56 NATO, and my only choice is which bullet, from 100yds, I wouldn't hesitate to take the .30 bore after seeing what I've seen. If I could opt for an AK with COMBLOC ammo, even better. 5.56 is no joke within 200yds from a carbine, I can assure you.
Other Variables
Past that, I prefer heavier pills of course. As to the AR10 frame having a performance advantage at distance, yes it does for energy. Now throw in the fact that you have to shoot from positions most of the time, and the heavier gun doesn't work so well, while a lighter carbine is very handy getting into positions with.
If I take 2 shooters of the same capabilities in marksmanship, physical fitness, and applicable skill sets, put them on a timer against each other, the shooter with the lighter carbine is going to have rounds on-target before the one with the heavier blaster. I've timed this in my courses, using 18" SPR's vs. 11.5" carbines, 20" 5.56 guns versus 7.62 SASS systems, HK417's, and so forth. Very rarely in a chance-contact scenario are you going to have first-round hits beyond the wind value threshold of the conditions, so that 2nd follow-on shot is critical. With a lower-recoiling, lightweight carbine, I can be spot-on quickly with the 2nd shot if the BC is good, whereas the 7.62 NATO throws you off significantly for follow-on. Sure you can mitigate this with a break and extensive training, but then nobody is going to have hearing to your left and right, nor will you inside the house.
A lot of guys find out quickly that even the 18" SPR with a bipod attached blows for getting into positions fast, but is an excellent prone gun. This is why I'm of the school of thought where I want the shortest, most accurate barrel I can get with tight twist, with the best BC bullet at moderate speeds. Granted, 5.56 sucks for energy as the distance increases past 400yds with the 77gr. So what if I could have a gun that handles like a 5.56 77gr, but hits more like a 7.62 NATO, with easy follow-up shots?
Goldilocks
Enter the 6.5 Grendel, 16" or even 14.5" carbine. I can get into positions quicker than the heavier gun, have a round out that is affected by wind less than a 175gr .30 cal SMK, with 50% less recoil, and 78% of the 175's energy at 500yds and 800yds. That is comparing the 123gr A-MAX, NCC, or SMK to the 175gr SMK.
I enjoy shooting all 3 cartridges, and have slung a lot of 5.56 M193 and M855, Mk.262 77gr, 7.62 NATO M80, M118, and 175gr SMK's downrange. I enjoy the 123gr 6.5mm from the Grendel AR15 much more. There is no recoil penalty, and I get better follow-up shots for a fast correction without need of a break. It's a lot cheaper to load for as well, considering the minimal amount of powder it consumes, and I have a better barrel life than 7.62 because I'm only in the 48,900-51,700psi range, which is even more ideal for longevity than the 5.56 NATO in an AR15.
So no, I haven't given up on 5.56 NATO or .223 Remington, but I have displaced most of it for the intermediate distance shooting that I do in my own personal shooting regimens with the 6.5 Grendel. To think I would have had more supersonic reach with a 16" AR15 than I did with the 24" M24 and M118 makes me hate that gun even more, and the .30 cal nazi's of Army Ordnance in light of better-thinking minds dating back to the .276 Pedersen, let alone the .280 Enfield.