Here's one for you bareshafting guru's. I found some old ACME shafts and thought I'd make up some arrows. They are 23/64" 80# spine weight and 9" tapered to 5/16". I usually shoot 80#-85# Surewood shafts cut to 29.5" with 160gr tips. So I cut these to 29.5" and stuck some 160gr. field pts. on a couple bare shafts. They hit right (weak for RH) by 8" or so. Really turned hard right! So, I took off the 160gr. tips and put on some 145gr...still too weak...went to 125gr tips and they were about right on the money as far as where it hit the target. The shaft was still nock left and tip right in the air as it got to the target.  I have never shot 125gr tips with 80# shafts...? I guess I am now! Just can't see why with a tapered shaft like these it would require so light of a tip.

I forgot to add that the shafts with 125gr tips and fletched with 4 4" fletchings flew great!

Did you happen to spine test the two of them?  The guys at Surewood Shafts have taken great care to make sure their spine tester is correct.  Many testers start to read incorrectly when you get into the higher spines.  Perhaps your 80# Acme shafts are not as stiff as they were marked.

What pound bow do you shoot?

I always check the spine and weight of the shafts to properly match them.

The bow is a cut to center 54#@28" Blacktail recurve. The cut to center allows you to shoot a wider range of spines.

That settles it then, Surewoods are just plain better!  

I AGREE Braveheart!!!!!!!!!!                  But it just seems weird that when tapered they react like this. I have made some up into arrows that weren't tapered and they bareshafted great with 160gr tips at about the same length...?

Tapering reduces the dynamic spine, therefor a lighter tip would stiffen up the spine .

Hi Snag the diameter of the shaft would make them behave 'lighter' too. The surewoods are a skinny 11/32 I have noticed, and fat ACME's are fat by comparison.
How ya' doing with those late season deer?

I wonder too...I've noticed that 11/32 bohning classics are tighter then 5/16ths on the same string.  COnsider a casual observation lol....but it sure seems to be true imho.   Which in theory would make the 11/32 arrows act stiffer.  

What tapering I have done it has weakened the static spine a few pounds depending on how long of a taper I've gone.  

Another thing that might come into play is physical arrow weight.  I havent played (YET) with the sure woods, have some on the way, but if they are quite a bit heavier they are going to act stiffer, then a lighter arrow of the same spine.

Add a lighter shaft, looser nock, and slightly reducing the spine by tapering...the three together could easily add up to a weaker shaft then expected.

Where's Bob when you need him ?!?!

Hi Bjorn, the blacktails have been a bit shy so far. I rattled in a forked horn buck. I spotted a good 4X4 trailing a doe, but could never catch up to him. Still 2 more weeks....I have a Surewood with a Doug Campbell damascus head that is itching to take flight!!!

AkDan, these ACME's were all in the 460gr weight before cutting and tapering the tip.  I know what you mean about the nocks. But with all nocks if they are not right I will lightly sand them until they just barely snap on and off.
I have a really nice spine tester. They are all right at or close to 80# spine weight...? Just can't figure this out. I guess I need some 125gr Eclipse heads if I hunt with these. Probably just use them for targets.

Bjorn is on the right track.  It's about the diameter of the shaft affecting the dynamic spine you need for your bow.  

If we were talking parallel shafts, you would need a stiffer dynamic spine for a 5/16" arrow than you would for a 23/64" arrow to have the bow be tuned well.  Said another way, the larger the arrow diameter pushes the arrow farther away from the center of the bow and you need a weaker spine to compensate.

Tapering the nock end of the arrow makes the arrow come off the bow more like a 5/16" arrow than a 23/64" arrow.  160 to 125gr tips isn't too surprising... it's only a little over one spine group difference (I need a 70-75# arrow for 160gr and 65-70# for 125gr tip)

Maybe barrel tapering would allow you to back to the heavier point, 5/16 in the back, maybe go to 11/32 up frount. Just a thought. I shoot the same spine on POC but I just use a straight shaft and get along well, I get mine in 11/32.

Interesting Jeremy. I just thought spine was spine no matter the diameter.

Spine IS Spine, but I agree that Centershot IS Centershot too and when you use a larger diameter shaft of any material it is going to change the centershot (and up/down from the nocking point too).