Strange Arrowflight

[Running Bear Eagle Eye]

G'Day
I shoot a hoyt trykon 60-70 pounds however at 70 pounds i cannot shoot broadheads straight at 70 but when i turn the bow down to 60pounds my broadheads hit exactly where my target tips do.
I know there is a bit of arrow rest collision when the arrow is released but if it shoots straight at 60 why would the same amount of arrow clearance make such a difference at 70.
I would love any advice on what could be causing this.

[PeterM]

Arrow spine is too weal I would say, try a heavier spined arrow.

[Running Bear Eagle Eye]

Thanks
i will try stronger spined arrows my current ones are have a spine of 300 so how much higher would i have to go for 70pounds

[Friar Tuck]

Arrow spine can be changed by a different weight tip. What is your exact setup for your arrows ie: Shaft length, model, insert weight fletch type and length and nock system. A lighter broadhead would stiffen the spine up a little.

Are you using a dropaway rest? At 70# maybe it is not dropping fast enough compared to 60# therefore creating a different launch pattern.

[Running Bear Eagle Eye]

I am using a drop away rest, my shafts are 29inchs long they are easton epic 9.1GPI with a 300 spine the broadheads are 125grain 3 bladed.
Im not sure of the insert and nock type but there is 5inch helical flecthing.
Also do you think that because the arrow is travelling faster at 70pound that a more compact broadhead is required my current ones are muzzy 3-blade with a One and three sixteenth inch cutting diameter.

Thanks