Length of arrow or % FOC changing nock high/low?

[JJB2]

Ok so here's the situation.  I'm shooting one beman mfx 400 cut to 29.75", with a 100 grn brass insert and a 200 grn point and one full length with a 50 grn insert and 175 grn point.  Both fly nock straight at 20 yds but the shorter arrow is flying nock low (pretty severe), while the longer arrow shoots with the nock just slightly above level.

Both are being shot out of my zipper sxt, ~57#'s at my draw length of ~ 28.5", three fingers under, bow is tillered for 3 under.

I've tried adjusting the nock and the relative difference in position stays the same.  Example: I tried 7/8" above and the shorter flew slightly nock high while the longer arrow flew dramatically nock high.

Any thoughts?      

[SS Snuffer]

Don't know the answer but I have the same thing with mine. 29 1/2 mfx 500 100gn brass and 150 gr.tip is nock high and full length with alum. insert 17gr. 150gr. tip is nock low. Split fingers, Kanait.  I took it to be be the hi FOC. (or my release).

[wingnut]

Why are you trying to tune two different arrows to fly the same?

Mike

[katman]

Same Q as Mike.

If you consciously or subconsciously use the arrow point in aiming the longer arrow hits higher.

[JJB2]

Mike, I like all my arrows to fly the same - like darts. If my nock is the right height and my arrows are spined correctly for my set-up, the arrows should all fly nock level to slightly high, bareshaft slightly weak, and all hit the target in the same group (right/left)...at least that's always been my experience.  

I like to set-up some lighter flatter shooting arrows for 3d, a nice heavy one for elk, intermediate for deer, etc.  I leave my brace height set the same and tune the arrows to my set-up so I can just change arrows and start shooting.  Typically the nock height is the only variable in how the nock flies down range, but since I've begun experimenting with the high FOC carbons I've gotten some strange results from time to time.

[Ragnarok Forge]

Try. Are shaft to torched shaft tuning.   It will help you fix the issue you are facing.

[Looper]

Clay, what? As Pete Hogwallop would say: "That don't make no sense!"

[troutguy]

im fairly new at this also but recntly spent a whole week end tuning a beeman ics 400. im a solid 29 inch draw. my 400 s are 30 inches from inside nock tp end of insert. im shooting a 50# kodiak mag.acording to the the charts i should  be shooting a 340. the charts are not always right. i also had a heavy insert up front shooting 125 gr points the arrow was in a group but 6 inches high. so in raised the nock point. that made the arrows porpus. i removed the heavy insert put my nock back 5/8 added a regular aluminum insert and 150 grain poit and im right on with good flght. so in my opinion you have to much weight up weight up front. if your arrows are not porpusing then its usually not a nock issue . and a 1/2 in of carbon arrow is not going to chage the spine that much. leave them at 30 inches put regular insert in and try 125 or 150 gr points one of them should  work fine. as far as penetration. thats enough to kill most big game on the planet with good shot placement. thats what worked for me, but it took 2 days and advise from a knowlegable friend to figure it out. my 400 ics beemanns are 8.4 gpi= 252 +150 point +20 GR nock and  insert =422 gr that will take down a grizzly
good luck give it try . hope it helps i just did this this past week.my guess is the 125s will work but also try the 150s.