RE: Draw Length & Arrow Length
Amo draw length is to the string, or better yet use an arrow to determine the draw length. Draw the bow with an arrow in it ( pointed in a safe direction) and have someone mark the arrow right above your grip, or where the hole is that the rest mounts to. Then let the bow down. Now measure from the groove in the nock to where the mark on the arrow is. Or I like to leave the arrow nocked and measure from the string to the mark on the arrow.
Now add 1 3/4 inches to that measurement and that is your AMO draw length.
If you have a 26 inch draw length 28 inch arrows would be considered long. Nothing wrong with that if you can get the spine to match, but they are longer than needed and will add more weight than you need if that is a concern. AMO arrow length is actually about 3/4 of an inch less than your draw length for a modern compound. Most shoot the same length arrow as their draw length, and that works pretty well in most cases.
I shoot a longer arrow because I like a specific arrow that spines stiff for my set up. A longer arrow will be weaker than a shorter one. Keep that in mind when picking an arrow. If you look it up on a chart or an online calculator it will base your draw length off from the arrow length you give it. If you tell it you are shooting a 28 inch arrow it will assume you have close to a 29 inch draw length. The arrow it suggests will probably be close enough to work, but will most likely be on the stiff side I think.
If you use a program or chart that goes off from your draw length and doesn't ask for arrow length and you tell it 26 inches, then use a 28 inch arrow you will be underspined most likely.
I use a program that lets you tell it both the draw length and arrow length so you can use whatever arrow length you want to and still get pretty close on spine.
Without actually runing your set up on a program I would guess you will want the 250's if they are the weaker spine. 350's sound a bit stiff for your set up, it is almost identical to mine except I shoot a bowtech mighty might.
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