I did some quick figuring and came up with some numbers, the 2018s you have are around 12.3gr/in which at 17.5 comes to 215.25gr, add 38gr for both inserts andaround 8gr for three feathers and I come up with around 265.25gr for a 17.5in shaft, add a 100gr haead and they should be around 365.25gr total

those 2216s are around 12gr/in so at 20in came up to around 240gr, add inserts(58gr) and vanes(30gr) and I come up with around 328gr, add a 100gr head and it comes up to 428gr


the other thing to consider is the arrow spline, in gereral an aluminum arrows diameterdetermines the spline(bigger around= more stiff) and the arrows wall thickness dermines its weight(2213 is lighter than a 2216 but the same stiffness)

even though(IMO anyway) spline doesnt play as important of a roll in short crossbow arrows, they still have a noticable effect, and lengths being equal, 2018's(which are 20/64 of an inch in diameter)arent as stiff as a 2216(which is 22/64 inch) even though they are very close in both weight and stiffness... cut a few inches off though and not only are you losing weight but your considerably effecting its stiffness, which would now make that 2018 more stiff(how much I dont know, I didnt figure that up ,its a littlemore work than I wanted to go through)


I dont know what your bow is rated at but IMO 365gr is a pretty light arrow(I wouldnt shoot themout of my phoenix) and are giving you alot more speed which is probably contributing alot to the better target penetration, theres also alot less surface area on the 2018, which means less friction the arrowhas to overcome penetrating the target

orit may just be that the better penatration comes from the fact that your bow likes and shoots the smaller, lighter, and stiffer arrows better, wobbily arrow flight(which may be what your getting with the 2216s) will kill penetration


I'dbe a little concerned about "string jump"in the bow with the 20/64 arrows but other than that, if they're working better, what the hell...