my BFSII with Wolf extra spring and Aim Surplus LW BCG runs even faster.....gotta be in the 800s, thing runs like a raped ape!
Do the same thing with the echo and you'll get identical results.
It's all a matter of making the cyclic rate of the gun itself faster, which is accomplished when you have a lighter carrier and/or buffer, heavier springs, excessive gas, silencer, etc.
The theoretical maximum cyclic rate of a BFS is slightly higher than that of an echo given the exact same upper, but it is far less reliable once it exceeds the cyclic rate of the echo.
This is because the BFS has the potential to let the hammer go before the bolt would normally trip the hammer, something the echo doesn't allow you to do because of the trip.
So, instead of that short delay between when the bolt goes into battery and the hammer hits the firing pin, you have a hammer that's already on its way before the bolt finishes locking up.
Sometimes, you can drop the hammer too soon, and instead of hitting the firing pin it rides the bolt home...once you hit that point you've exceeded the cyclic rate of the bolt and will get intermittent operation.
That's why Franklin recommends the lighter carrier and heavier spring, so the cyclic rate of the upper is just a tiny bit faster than the speed at which most normal humans can manage to wiggle the trigger.
Put the BFS on a slow/chunky upper, and you're likely to outrun it...but the echo will keep on ticking like normal.
Years ago I did the paperclip mod to my mini-14 (the original binary trigger mod that resulted in the ATF letter stating these are legal).
I had already done some work to the trigger to reduce the pull and eliminate all but the most necessary travel on the trigger, so it was really easy to make it go fast.
Unfortunately, my mini has a pretty slow cyclic rate, and I had a hell of a time just getting it to pull doubles without overrunning the action.
It was a lot of fun when it worked though, and for the price of a paperclip the fun:money ratio was spot on
