i have the np cocking is rough, cant get a reasonable shot group getting ready to replace scope that came with it to see if it helps, And it's heavy. Compared to gamo wildcat whisper which has better trigger, still using junk gamo scope that came with it and it works, lighter better for carrying in field, shooting great compared to NP. Tin can of premiers were ok but JSB diablo match seems better in both, Considering I paid double for the Np over the gamo I'm a little let down.
I should say that I havn't shot NP much to many fliers to even try finding the best pellet. But I think that is more about the packaged cp scope.
This came out longer than expected, lots of general ramblings, sorry. Not exactly specific to one person... But could help. Some of it is known to many, some might be unknown to new comers and some folks might disagree with what's said. They can correct me if they wish, good and/or better knowledge is better than ramblings from myself, Lol.
If the cocking cycle is rough, your gun could probably use some lube. Don't put anything into the transfer port, that is unless you like changing piston seals (there's only one instance I'll recommend a drop or two of pure silicon oil, but it's a lazy fix and will detonate). Usually it's the rear/top of the piston skirt dragging/galling against the compression tube causing a rough cocking stroke in NP guns. Best thing to do is take the gun down, degrease and relube with quality lubes. You will need a spring compressor.
I don't recall if you can easily lube through the cocking slot or not on the NP guns, but worth a try if not willing to take the gun completely down. You'll have to pull the action from the stock, it's recommended to use a little bit of high moly (60% or better) grease, but honestly you can get away with cheap synthetic grease "with moly" (...inexpensive airgun stuff, don't roast me, Lol). Just know the pricier stuff costs more for a reason, but the cheap stuff will work to at least smooth things out. The less you use the better, too much will make the gun temp sensitive and off-gassing of the grease may lead to a shorter piston seal life/more dieseling/smoke (not detonation). Just a quarter to maybe half pea size dab of grease is all you really need if you can apply to the chamber wall behind piston skirt, through the slot located on the underside of the action (probably it's too much, but applying through the slot is tricky vs taking the gun down). Alternatively you may still be able to find RWS chamber lube or Tune in a tube, but they're pricey for what they are. There is an alternative to tune in a tube, but forget what it's called. Since NP guns don't have spring vibrations you need very little grease, you're just lubing the chamber wall/piston skirt, not dampening a spring. For a grease syringe idea that's potentially free, pharmacy's usually give out little plastic measuring syringes for children's medicine, I have not tested these out but thought of this when seeing them. Otherwise find a thin applicator of sorts. I found high content moly Loctite anti-seize paste cheap, which I have used before... Just not in NP guns. After lubing, the gun will smooth out after some shooting, this will spread around whatever lubes chosen. Oh, while the gun is out of the action, snug up the pivot bolt, not super tight just ensure it's snug "enough". Some have different views as to how tight is too tight, but generally just snug enough to hold the barrel in place/up (not latched) after cocking is acceptable, while others say to have the barrel "just fall" after cocking... Test and do as you please, but don't cock the gun out of the stock.
One thing about pellet testing, especially after shooting Crosman pellets... Clean the bore really well. They're so hard that after they season the bore, other "softer" pellets (JSB or even H&N) just can't get a good seasoning for hundreds and hundreds of shots, especially if one hasn't gone through the lengths of bore polishing. Some might feel this is speculation, but my experience has been otherwise. It won't reduce fliers so much as you'll find generally better groupings. Also, after bore cleaning it may take up to 50 or even 75 shots to fully season a bore and realize a pellets full potential. At least give it 30 shots after cleaning when testing various pellets. If all accuracy goes away after cleaning don't fret, just shoot more. As for actual barrel cleaning, there are many suggestions that come up. Everyone has their own recommendations/methods and supplies they prefer. You can get away with weed-eater line, cotton patches and solvent/lubes of choice. I generally just use Ballistol, but have used Hoppes, Remoil and etc...
Lastly, some guns have inconsistent barrels and just will never shoot well. You might get away with polishing out tight spots, barrel crowning or even barrel chopping to fix accuracy woes. I've encountered three Crosman/Benjamin break barrels with plain bad barrels, but I've had many examples.
If you've made it this far, thanks for reading. If you have better advice please share, I'm no pro. Take care and shoot safe.