The 340 Surgical is 8.2 GPI...so there's some weight differences between them. The components are different too. Not sure which Beeman you're shooting either, and you didn't say whether the arrow lengths were the same either. There is way too much stuff we don't know just to be guessing. Lighting and chronys are very important...the spot the arrow went thru them at, distance you were from it, etc. Thus a 5 shot average is best to determine readings out of one. I can tell you from the speeds others are posting at Archery talk, the Insanity is for sure more efficient at shooting lighter arrows than heavier ones. Several have done speed tests on them against other bows using progressively heavier arrows, in say 10-25 grain increments, and for some reason the Insanity comes out of the gate blazing fast with light arrows, and then this SIGNIFICANTLY drops off with heavier shafts...vs the other bows with similar specs, that with each increase in weight, they average about the same amount of drop in speed. The Insanity was blazing for say, IBO of 350 grain arrow - 380 grains...and then once it hit the 400 grain and beyond weights, the bottom fell out of it fast.
One of the recent tests, puts it against a Prime and Strother Rush, same specs, and AMO draw length within 1/8 inch of one another. Out of 60 lb bows at 29" draw the Insanity blistered the others by quite a bit with lighter arrows...300 grain IBO arrows to 350 grain. The speed gap between it and the others were quite significant in favor of the Insanity being faster. Onward to 400 grain+ arrows, and the gap wasn't no where near as wide...as noted, it's like it hits a wall with heavier arrows. Quite interesting.
