Round count would help, since a broach cut barrel will group tight, then wildly open the groups up around the 4K mark (button rifled barrels last about 8K until the groups spread gradually too wide instead).  Throw in over heating a barrel, and these numbers greatly decease as well.

The fact that is short stroking, or rather over function in your case with what may be the bolt opening up to fast, could mean that the barrel gas port may have plasma eroded, and this is causing the bolt to unlock isntead.

At this point, really time to pull the barrel off the rig to not only check the chamber and throat, the rifling, but the gas port size and even barrel crown with last few inches of muzzle bore.  With these checks, should be obvous what the problem is, and if still a low round count, the barrel may be able to saved.

At less than 2K, could just be build up in the barrel that really needs to be cleaned (including cleaning the crown as well).

Hell, you don't state what FS or brake in on the rifle, and in regards to 2K of rounds with most breaks, between muzzle fouling build up and plasma erosion to the brake, the lack of accuracy could by all right there from just those two.  Also, if you have been shoving a cleaning rod down the muzzle to clean the rifle (instead of inserted from the chamber), could have screwed up/worn out the last inch of bore, and that is going to cause the barrel to shoot like shite as well.

As for ripping the cases in half, again combo of over function, and could even be that the chamber really need to be scrubbed clean with chamber brush and good copper solvent like Sweets copper solvent.  Hell who knows, and you may have a ring of cracked off  neck brass stuck in the last of chamber cut, it cause the over function from the reduced blow by at firing forming of the cases, and this is causing the over function instead.

Or could just be shite hammer and recoil spring that went weak too fast, and this is allowing the bolt to unlock too soon isntead.  Normally, the recoil and hammer spring are changed out about every 4K rounds, but if you ended with cheap import springs made from inferior metal, could explain the problem with the bolt unlocking too fast instead.

So again, pull the barrel, give it the needed cleaning with a good copper solvent, and then start checking it out.  The chamber should be smooth as a babies ass with no reamer chatter of grooving, the crown should be perfect with no flaws, and the last of the bore rifling should be just as sharp as the rest of the rifling.  If you are running a brake, check out the inner blast sections for plasma wear and if it too great, then the brake needs to be replaced.
To note, when installing a brake, do not over torque it, or you will stretch the last inch of bore (last of threads to the shoulder section), causing the barrel to shoot like shite as well.

Again, lets break this up into two problems,

The first is the bolt unlocking too fast, the spend round stuck in the chamber due to the higher residual pressure in the bore and ripping cases in half during the pull.
Since we are dealing with Fed gold ammo (uses slower burning powder, which will increase the barrel gas port pressure), then either the chamber is not mirror smooth and needs to be chamber brush cleaned, the gas port has eroded and now allowing more gas to the action, or the springs have gone soft and them allowing the bolt to unlock too soon as the residual pressure in the bore is still too high.  

This is the first problem that needs to be solved, and that is to get the bolt unlocking at the correct time by checking the above.


Now regarding the second problem, being that the accuracy dropped off, some of that could be that the action is unlocking too soon (with even bad feeds canting the bullet in the case on loading), could be build up fouling/erosion on the brake /muzzle, or could be that the rifle just fell off the mark quickly instead.
Note, on CMP rigs that we had to run the FS before the ban, the inside of the FS was increased in angle taper so it did not effect the gas path over taking the bullet on the way out (both Mia and the AR's).  With a brake on the end of the barrel, it will effect not only the gas path on the way out as it over takes the bullet, but the barrel harmonics as well.  Come the ban, it was a god send since you no longer had to run anything on the end of the barrel, making for not only easy cleaning of the crown, but not having any added weight on the end of the barrel to change the harmonics as well.

In regards to the second problem, there is a real easy test to tell if the barrel is really cooked or not, and that is to take the action and brake out of the math.
Clean the chamber with CLP and a chamber brush , pull the brake and clean the crown/muzzle, use some solvent to get both dry, then single sled one round at a time without the brake on the barrel to test just the barrel.  

Also to point out, when I do a full clean on a barrel, will pull it from the upper receiver as well.  This way, when I go to put the barrel back on, know that the torque to the barrel nut is correct and not one of the problems (Loose barrel nut and it should be between 35ftlbs at least and up to 80ftlbs if needed to index the barrel nut top spine void/channel with the upper receiver channel to make sure the barrel nut is not binding on the tube), as well as checking to make sure that the tube is correctly aligned with the carrier key.