I do not have a discovery nor have I ever heard one.... This is my first PCP. So I will try to best describe the noise level.
For me sound, accuracy and quality was a very big concern. I have not been able to test the accuracy. Pending receipt of my scope. But I can tell you the build quality and sound levels, to me are very acceptable. The sound level of course will very based on the power level. I did play around with the power levels. there are basically 5 power indication marks. At full power, compared to my springer guys, I would say the s410 is quieter sound. The sould of course is different compared between a springer and PCP. At the lowest power setting the s410 is super quiet. I think I have read before comparing to someone spitting. It is that quiet. When standing behind the gargare while someone else shoots, I can just barely hear it fire at lower power. I would say this is me standing approx 15 yards away.
Accuracy still pending, but the other requirements, I'm very happy so far. And the Walnut stock, I'm pretty happy with it. Mine arrived with a pretty nice stock as I was hoping for...
I'm sure others will weigh in on the noise level comparisons.
