Arrow spine question

[Black-N-Red]

Shooting a Hoyt Spyder 30, 60#, 30" dl, shooting FMJ's 340 spine, 100gr head. Field points group awesome can stack them at 40yrds. Swap out to my Ramcat's, they hit left, no matter how much you move the rest. Put on a 125gr Ramcat hits slightly closer to the feild point but still to the left. Picked up some cheap GT Cut-Off's from academy in 400 spine now they hit within an inch of my feild points at 20yrds. Also with the 340 spine my mechanicals hit all over the place, but with the 400 spine they group. I'm sure I answered my own question I'm pretty sure I need to shoot the 400 spine. But all the charts show i need the 340. Just trying to make sure before I spend the money on some FMJ's in 400 spine

I should mention that I have a 50gr brass insert up front also.

[jljjdye]

I have a brand new dozen Easton axis ready to shoot cut 29.5 in 400 spine that I would swap for the 340 spine you have if you want.

[Black-N-Red]

I have a brand new dozen Easton axis ready to shoot cut 29.5 in 400 spine that I would swap for the 340 spine you have if you want.

I appreciate that, but I also shoot these out of my Arena 30 & Nitrium Turbo.

[old killer]

Remove the 50grains and retry. The best way to check spine is to make point weight adjustments of 50gr or more and re test.
If the 400's are grouping field points and broad heads together, I wouldn't change any thing for accuracy.

[Dave_]

Sounds like a different tuning issue. Probably cam lean... There shouldn't be that much of a difference between 340s and 400s. 400 spine arrows will be more forgiving because the flex will stabilize the arrow faster. So my guess is cam lean, or maybe a slight timing issue