I had an HW50 in .177 with a full maccari tune kit that did 850 fps with standard pellets.
Do a search for James Maccari it will pop up.
To me it was the best if could find as a high power air rifle, very light, 14" barrel transfers the weight back to the stock, very compact. The handling characteristics are much closer to a rimfire. versus the awkward forward weight often found with springers with 18"+ barrels. Yeah another plus for the record trigger! It produced enough power that i was able to mount a small 4x scope and not have to adjust it from 25-40 yrds
Accuracy it was like a freaking lazer beam.
As for the low points, there is a link in the cocking arm to shorten the stroke lenght so you get a much fuller forestock which makes for a much heavier pull than a rifle in a simmilar class.
Unfortuantly i swapped it for a killer deal, finding that i want to relpace it i bought one in .22 PAL version and it appears to be shooting under 500fps, By the way im ScottC's brother
IanC