Adding foc changing spine?

Joined
Feb 15, 2021
Messages
71
Im shooting a 70 lb compound bow, my arrows are cut to 29 right now. I ordered some carbon express D stroyer 350 spine arrows. I shoot a 100 grain Broadhead/ field point. My question is, can cut them down to 27 or 28 inch and add a 50 grain insert for more foc. Will this weaken the spine of the arrow or am I still good for a 350 spine. Hopefully yous can understand my question!, thanks.
 
Joined
Jun 21, 2019
Messages
2,547
Location
Missouri
Pinwheel spine calcs suggest shortening the arrow 2" would compensate for the extra front end weight and effectively stiffen the arrow slightly.

29" C2C with 100 gr point, 15 gr insert, 9 gr nock, 3 vanes at 7 gr each:
Screenshot_20240828_233349.jpg

27" C2C with 100 gr point, 50 gr insert, 9 gr nock, 3 vanes at 7 gr each:
Screenshot_20240828-233404_qSpine.jpg

Assumed bow specs:
Screenshot_20240828_233455.jpg
 
OP
T
Joined
Feb 15, 2021
Messages
71
This is what I went by so hopefully they shoot ok, what are the symptoms of a week spine?
 

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