i have ran the k2 3500 and k3 4800 great packs but now i run the kuiu pro 3600 it is really comfortable folds down really small but expands to do a couple over nigh trips. i walk 3 miles 3 times a week with 40 pounds in it no problem really comfortable
it all depends on the bullet manufacture copper normal takes a faster speed to have a more reliable expansion than led they say copper is normally around 2000 fps where led is normally around 1600
i have 4x16x44 and 6x24x50 awesome scopes hard to beat for the price i have shot them out to 1300 yards they track really well and really positive clicks in the dials