I have repaired dozens of targets with Great Stuff, some of my targets are 30 years old and still shootable. The key is to repair them before they get to shot out. Most clubs will
l sell you a shot up center section for little or nothing so I have a few spares.
WARNING! Don't let your wheel shooting buddies shoot your patched targets, trad only, wheels will shoot through these patched targets in short order..
I have a new expanding foam that is supposed to be much denser than Great Stuff but haven't tried it yet.
Here is my process on a really bad target, it fell apart on the way home, I paid $5 for it.
Bad shape
Taped and ready for foam, I used old arrow shafts to hold the parts together for the
correct alignment
I remove the plastic, rasp the expanded foam back to the original shape and color match the paint (rattle can) with the original.
I did these three on the same day;