I need some more .38 Special ammo, and Freedom Munitions is having a $7.50 flat rate shipping offer this weekend. I was about to get some of their 158 Grain RNFP at $137.50 for 500 rounds. Shot the ammo before with no issues, but for $10 less for 500 rounds they are selling 158 Grain HP ammo. Why would that ammo be cheaper ? Is there something I'm missing ? What might be better for plinking ?