From our favorite bullet collector Mr Kevin Gross, I bring you a couple gel shots of 87gr PRL compressed tungsten loads. Like the 79gr and 150gr subsonics, these were very cool to test!
Macros:

Neat.

My recollection is that in the 1990s, there was an article in Precision Shooting about this round.  It is also mentioned in the book, The Competitive AR-15.  During the 1990s, there was a lot of development of heavy bullets for the .223. While PRL bullets attracted interest, they were always very expensive. Development of other heavy bullets such as the Sierra 80 grain MatchKing made the AR-15/M16 rifles competitive at 600 yards in high power competition.

Powell River Laboratories (PRL) "Bubba Bullets" (named for their inventor) were-are ingenious.  The US Government had/has several users.

They had several distinct advantages in that for the same length as a 77-grain Matchking they were less affected by wind, requiring a LOT less windage.  They provided such an advantage that one of my predecessors as USAMU Commander, Colonel "Mac" Johnson, decided the Army Team would NOT use them, as they provided too big an unfair advantage due to their prohibitive cost (much like Bofors M995 tungsten bullets, the projos themselves cost over $1 apiece around 2000) and the fact that the critical core component, tungsten, was-is primarily sourced from Red China.

There was also some concern that it might be difficult to provide medical care for a frangible cartridge wound.  Another down-side is ineffectiveness against hard-plate body armor and hard barriers.