Slightly longer barrel looks better, but stock barrel is accurate.
Shot to shot consistently
Very smooth, zero kick
Does not chop, ever.
Battery from the factory is crap.
Preferred to have 45degree rails
I feel this marker is even in the wrong section of this site, as it is not a blowback marker with e-frame, its is a full blown electropneumatic. Note the Vibe (speedball clone of SP-1) is listed in the 'high end electronic' marker, not 'low end'.
I bought one of the first SP-1 the week they were released. My very first impression worried me because I aired up the marker, and it wouldn't fire. The battery from the factory was no good, and when I replaced it.
Since this time I've put 8000+ rounds though the marker in varying conditions and have never once had any problems with the marker, and it never once has broken a ball in the breach..
I had a batch of paint that my spyder TLR with the ACS bolt was breaking about one in 20. I took the same loader and paint from the spyder and put it on the SP1, and ripped off 200 rounds as quick as possible and no problem. The electronic trigger on the SP-1 is far better than the mechanical of the spyder.
I use a 68/4500 hpa tank, without the wedge at the asa, and this makes the tank fall in just the right position as a stock.
When firing the marker is extremely smooth and consistent, which helps with accuracy, and allows very tight grouping of shots with no dropoff.
Maintenance is pretty easy with the bolt-out-back, as I find I spend more time cleaning rails than it takes to clean the internals.
I would highly recommend the SP-1 as it's one of the best mil-sim markers out there regardless of its ultra-low $150 price tag.