At a Practical Rifle match when the AR15 was NOT restrictred, we had a fun "Jungle Trail" that ran maybe 150 yds. Don't recall the numbers of targets. No target more than 25 yds away. The rest of the match was on paper on the usual range, a quasi-military run down.
IPSC targets were placed behind trees to partially screen them and partially hidden by shrubbery. There were two categories - bolt action and semi-auto, no restriction on calibres in either.
When scoring an AR15 shooter, he was astounded to learn that his double taps had not penetrated the shrubbery to hit the targets more than once, the bullets deflected by the twigs. Other shots were deflected off trees and missed the targets.
On the other hand, the guys with the 'retro battle rifles' (Springfields, Lee-Enfields, Mausers, Moisin Nagants, Garands, M1A's) shot thru' green trees 4"-6" and hit the targets behind them! Brush and shrubbery was not an issue.
The match winner on a couple of occasions was a US school teacher from Wenatchee, his rifle a scoped Remington 700 in .25-'06. He also kicked our butts in pistol shooting with his matched pair of King's Custom Gunworks .45 Commanders.
About this time, there was an article in "American Rifleman" from a US Army Captain who reported an incident where the AR15 failed to do the job. His people were in reserve, watching a firefight from a vantage point. A Viet mortar crew set up at 200 yds not knowing that they were under observation.
He called up a rifleman to engage them. The soldier emptied a 20 rd magazine without hitting anyone and the mortar crew did not know they were under fire! They were screened by jungle shrubbery. He then called up his M60 gunner and indicated the target to him. The gunner rapped off single rds, killing all members of the crew.
Lesson learned - the 5.56mm was not the ideal weapon for the purpose.