Unless its super heavy, its just a timing thing That whole notion of shooting a Bill Drill and judging the spring from where the holes end up on the target is fundamentally flawed due to a failure to account for timing. I kind of doubt that he's got something as heavy as 20# in there, so...
ETA - one of the really cool things about high speed vid is that it lets us actually see stuff like this vettman1 could also learn some things from comparing the video to his perception of the dot movement (ie, does he see it dip down past point of aim on each shot). Someday, I'll convince shred to come out to the range with me and bring his camera along... I've been curious about how I actually do some things, too...
The spring is the standard light recoil spring that comes with a recoil master.
I can see the dot move up and then down past the point of aim.
I have no idea exactly what my splits are, but I'd figure when I'm shooting at the fastest rate they're somewhere between .14 and .2. That's where I usually am when I'm shooting fast, but it's only a guess so take it for what it's worth.
If you look at some other videos that I've posted there is one of me shooting a 1911 in .45 and a buckmark pistol .22. The .45 dips as well. Probably because I'm over compensating for the recoil. Funny thing though, you don't see the .460 dip down... :-) of course my spit times are much longer when I'm shooting that.
One last thing to note, Dan makes a top notch, quality gun and it's fun to see go slow. I think that is mostly because when you normally see Dan's guns, they're going so fast!