Adding foc changing spine?

[The big greasy]

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.

 

[Mighty Mouse]

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:


27" C2C with 100 gr point, 50 gr insert, 9 gr nock, 3 vanes at 7 gr each:


Assumed bow specs:

 

[Bump79]

What is your draw length?

 

[The big greasy]

What is your draw length?

Right around 29. My bow says ibo speed of 330. It’s 36 inches axle to axle. It’s a Ross Hit target.

 

[Skerhunter]

A 300 spine with 50gr insert would be more ideal at 28-29”.

 

[Bump79]

Right around 29. My bow says ibo speed of 330. It’s 36 inches axle to axle. It’s a Ross Hit target.

I agree with @Skerhunter a 300 spine at 28.5"ish would be ideal. I'd put 175 total up front to weaken it some.

 

[Wilderlife]

Another vote for 300 spine. 350 may be working OK but a 300 spine will almost certainly be better.

 

[The big greasy]

This is what I went by so hopefully they shoot ok, what are the symptoms of a week spine?

 

[Skerhunter]

This is what I went by so hopefully they shoot ok, what are the symptoms of a week spine?

Difficult to tune - less forgiving if you do get it tuned are your symptoms.

Basically it takes your arrow more time/distance to correct/stabilize in flight.

 

[Wilderlife]

And although it's hard to measure, a stiffer arrow will almost certainly penetrate better than a weaker arrow.