Congrats on the new rifles!! I've only tried the Rem UMC ammo in my .22-250 Ultra, it doesn't shoot well, so I can't help ya with factory ammo there. I shoot handloaded 50gr Vmax and H4895 that works very well tho.
I have four 17hmrs, one of em is a Sportster, after break in, I don't clean it until accuracy drops off, then it takes 20 -30 shots after cleaning before it shoots good again. You'll do well for yourself to polish the bore per the FAQ info, it will save you some range time. You may need to try different types of ammo to find the best, just like any other rimfire.
Tim