Easton Axis 500 spine arrow tuning input

[CRS]

My son is shooting 4H archery.  He busted up his hunting arrows already, which is a good thing. I immediately switched him from shooting bullseye to 5 spot target faces.

I want to make up some Easton Axis 500 spine arrows for him.

Here are the particulars.  He is drawing 26", and approx 43-44# out of a 50#@28 Bear Black Bear Bow

I have some 500 spine Beman MFX arrows cut @ 27".  But it takes a 250gr point to tune them per Adcock's method.

Is the old guideline 1" for every 25gr?  That would equate to 31".  But his hunting arrows are Beman MFX 400 spine cut to 31" and shooting 145gr heads.  He shoots these well and has killed deer and turkey with this set up.  So the math doesn't add up IMO.  

What length should I cut the Axis to use a 145gr head?

I am just trying to get close, so I do not have to go through the cut shorter, refletch routine, cut shorter refletch routine. I am thinking 28.5".

Any input would be appreciated.

[katman]

Beaman mfx is heavier in gpi so would tune as a weaker arrow than the black axis hence the need for 400. My guess and its only that, probably 30".

Fletch one full length but put the fletch further down the shaft maybe and inch or two, arrow will fly fine and leave you room to pop the nock and cut.

[CRS]

Ah, thank you.  

Did not know that lighter gpi causes higher dynamic spine.

So does the 5# dynamic spine per inch and 5# per 25gr point still apply to these skinny carbons?

I love the satisfaction of my woodies & cane arrows.  But it is very nice to be able buy exactly matched spined arrows and have a dozen made in roughly 24 hours.  Much less time consuming and labor intensive, but they do cost more upfront in hard earned cash.

[The Whittler]

Get your hands on a couple 600 spine shafts. I think they might work.

[Friend]

To shoot the Easton axis 500 w/145 BH may likely take you to 30+"'s

To shoot the Easton axis 600 w/145 BH, could likely put you in the range of ~28 -28.5"s.

Many factors could change this since it is an estimate based on your current MFX being the benchmark.

[SS Snuffer]

This works for me at 28" draw.

[Bill Carlsen]

My wife shoots 45# @ 26" and I make her arrows with 500 Beman MFXZX shafts which are the same as the Axis. She shoots them beautifully when cut to 27" and a 200 grain head.

[Bowmania]

I'm shooting .600 Axis with 285 up front.  My bow not cut to center is 49 at 29.

Bowmania

[CRS]

Thanks for all the replies.
The results are in.

Tried crunching numbers and decided on 29".

Did up two fletched and two bareshaft.  Tested them this am.  

145gr showed a touch over spine.
175gr is ded nutz on.
200gr showed slight weak.

I am satisfied, the 175gr tip bring total arrow weight to 440gr and put's it right at 10gr/lb.

Nice thing is, there is adjustment room.  As his draw length grows and poundage increases.  I have two options to increase dynamic spine.  Shorten arrows or decrease the point weight.

If he happens to draw an elk tag, weight tubes, or cut an inch or two off increase up front point weight for extreme FOC to aid  penetration.