8KG OMW spring does the job just fine for superstock and will be maxed on the field in terms of effective use with a proper air tight breech. I've spoken with Heng of Xplorer and he advised me that their 18kg spring is near identical to OMW's 10kg spring, but the majority of springs they sell and install in their blasters are the 14kg variety (which in reality is comparable to the omw 8kg spring). Anymore load then that and you send darts farther but the wind will take them off into the sunset. Its not range that's important, its effective range, the distance where you can accurately hit stuff a good majority of the time. If you rely on long range pot shots then just angle your blaster 45 degrees and spray and pray.
I've found that most "aimed" shots that hit after a year of warring happened at 75 feet or less; even if many shots may have landed and or hit at further distances it was more practical to wait for a close engagement distance instead of spamming and wasting ammo. If you're building up something greater then the needs of an 8kg spring it'll hit harder at a higher fps but from my experiences won't necessarily be anymore accurate.
I had 14kg in my LS and it was hitting 220fps maxed on the chrony with elite darts, they hit hard and can shoot through cardboard box layers but I personally didn't want to get hit with that and I knew most others wouldn't either at a super stock game with a mix of kids and adult players (if you are going to start tickling this range, just go to NIC homemade wars and fire stupid power airblasters and leave welts). I also realized after rapid priming my arms would get tired after a while with the 14kg springload and I wasn't pulling back the shotgun grip all the way to catch and then get a lot of misfeeds. The performance with various strength springs at a short distance wasn't different enough to justify the huge load springs and sacrifice rate of fire and reliable priming.
One hand priming the 8kg spring is possible, but for that I recommend the stage 1-2 omw kits that come with a polycarbonate high impact bolt sled. The stock sled will bend and twist and snap with one hand priming relatively easily with 8kg or more spring loads (i have broken one myself even using a shotgun grip, which is essentially 2 handed priming as it pulls from both sides evenly).
Best of luck with whatever you decide to do.
Thanks so much! Should I just use the oznerfnerd spring?