PTR-91/HK91 will run on what every you feed it.

The trick to reducing felt recoil though, is to change the standard buffer out to a heavy buffer isntead.

The standard buffer has a very short stroke, and you feel the bolt hit hard off the buffer at the back of stroke.  The heavy buffer has a much longer stoke, and really smooths the rifle's felt recoil out instead.

Yes, Hornady make a very good bullet, and prefer the 150sp over the 150 FMJ for two reasons.

The SP's will expand when you need them to for hunting type purposes, and since the SP puts the bullet cup's opening at the front of the bullet as part of the SP design, this means the base of the bullet is not open with exposed lead like on the FMJ design, which allows the SP bullet to shoots a little tighter isntead.

As for a plinking type bullet, then the 147fmj's are not a bad bullet for just carving up the country side.
Hence General dymanics is the one running the LC plant now, so the 147 gr bullet from them in the below link, is the same bullet used in the current military M80 ball ammo.
Note, its not going to shoot at tight as the Hornday 150sp bullet, so keep that in mind.

https://www.wideners.com/reloading-supplies/bullets/rifle-bullets/308-bullets