I've spent countless hours bareshafting to find the perfect combo for my Big Jim Buffalo bow.  The bow is 51# at my 28" draw.  I found that GT 3555 Trads cut to 30" with 100gr inserts and 175gr points bareshafted perfectly and that Beman or Easton 500's cut to 30" with 100gr. inserts and 250gr. points bareshafted perfect for me.  When I say bare shafted perfect, I mean they flew like darts with no wobbles and grouped with my fletched shafts out to 25yds.  Well I've acquired A LOT of those shafts because they flew so well.  Imagine my surprise when I strapped my big ol' Magnus I 4-blades on the ends of my arrows tonight and shot only to find that they were way underspined!!  I always thought Stu's spine calculator just didn't work for me because when I bareshafted the arrows that it said would work they were always stiff.  Well those same arrows fly great with a broadhead on the end!  I've bareshafted and then broadhead tuned before with woodies and aluminum and everything worked out perfect but this time has really got me stumped.  I'm gonna do some more testing tomorrow if I'm not too sore (I've been shooting for about 5 hours trying to figure it out).  I had an AD Tradlite woodgrain cut to 30" with standard insert and 175gr. head and it flew really well and a GT 5575 cut to 29" with 100gr. insert and 175gr. head flew well.

Well time to rest the shoulders.

How far underspined are they with the broadheads? Do you have any of the 50 gr inserts? That might be enough to bring them back.

I figured you were way weak half way through your post.  Been there and done that.  Carbons have had me scratching my head a few times unlike other shafts.   I have been able to get a carbon to tune bare shaft when real weak.  All that FOC I think. I also have some tuned now to my bow that are somewhat weak on Stu's calculator and others that are about spot on.  Both shoot great.  However, the weaker set-up is much less tolerant to point weight change or maybe more depended on how you look at it.   What I find is a little change in brace height or point weight makes them not shoot as tight groups.  The bare shaft flies to the right spot, but something is just off.  Long range bare shaft can correct in flight after 20 yards or so.  I can add weight and take it off of these arrows, and I don't get a noticeable move weak or stiff.  I just get less tight groups.  

I figure the quick reactions of carbon with the high FOC does something that can cause some kind of timing thing to work out for me with different set-ups if  I hit the sweet spot.  I think for me a lot of overhang on my shaft does something also with some kind of whipping effect, and when I hit the sweet spot it works.  

What I have done now is move more in the direction of Stu's calculator, but with shorter arrows.  I did this first because I had a pile of arrows with slight dings on one end or the other.  I cut off a inch or more and got a safe shaft.   I started playing with shafts no more than 1 1/2" longer and most more in the 3/4" - 1" longer than my draw.  Then I loading up the end until they shoot well with a fine tune of a 1/4"-1/2" cut.  Often I found I had a much shorter arrow, but same point weight or less point weight.  I looked for a noticeable move from stiff to weak with point changes.  No kind of different, but real noticeable shooting stiffer or weaker by adding or taking off 25 gr. or changing shaft length 1/4".  Now my arrows fly better and more consistent with slight variables, and show clear weak or stiff with changes.   My current arrows are:

GT trad 5575 30 1/4" 50 gr. brass and 175 point
GT trad 5575 29 3/4" 100 gr. brass and 125 point

Note that they are close on length and have the same point weight, but the second has a longer flexing shaft length by almost 1" due to shaft and insert length.  The first is the one that shows distinct difference in point changes while the second is the one that can be vague on stiffness changes and looses accuracy with slight brace changes.

Bareshafting is not for everyone. The objective ought to be perfect arrow flight and whatever method you choose to achieve that is up to you.

I agree with Extreme, I have the same full length GT Trad 35/55's & all I did with mine was the standard insert, 10gr. weight adapter, 1" piece of 2117 shaft & a 125gr. point {163gr. total up front} & they shoot beautifully out of my  51* @ 27.5" Zona T/D recurve even with a woodsman on the end once I have em spinning right.
But then again my BH is dead on 7.5" w/ 14 strand B50 too, if you're using 8125 string or similar or less strands than I use it will make the shaft that much weaker due to it's lighter string.

A broadhead of the same weight as a field point will not bareshaft the same. Because a broadhead is longer, the weight of the broadhead is further forward, thus weakening the spine.  As a general rule, the shaft will have to be about 1/2 to 3/4 " shorter when shooting a broadhead of the same weight as field point.
People say never bareshaft a broadhead, it is too dangerous. That is correct, but I have a safe place and have done a lot bareshafting of both, comparing field points to broadheads. You will need a lighter broadhead if you want to shoot the same length shaft or a shorter shaft if you want to shoot the same weight point/broadhead.

I too have done a good bit of bareshafting with broadheads, and although I completely understand John's post above, I myself have found broadheads of the same weight to bareshaft just fine. Also, John Shultz once told me that he needed heavier broadheads to have the same point of impact. He wasn't referring to spine though. He was referring to flight as he contributed the variation to aerodynamics as he said him impact was sllightly higher with broadheads and so he shot broadheads that were about 15-20 grains heavier than his field points. I myself am not good enough to notice what Mr. Shultz was speaking of so I just look for good arrow flight...so I stuck with bareshaft testing (I too have a safe place for such).

Waitaminnit...

Did I misunderstand or were you bareshafting a broadhead?

What kind of bare shafting were you using?  There's tuning, planning, and thru paper.  Since you mention grouped, I'm assuming planning.  I use planning with thru paper and fine tune with FP and BH.

After 5 hours, I'd bet that if you start with the same setup as you quit with you won't get the same results when you start again.  Try FP and BH when you start and I'll bet your not off as far as you may think.

Bowmania

Put some feathers on the arrow and if they shoot well, use them.  

I know folks like to try to get "the best flight they can" and go to extreme measures.  I also saw my buddy spend an entire summer screwing around, spending all sorts of time, effort and money to get something that would fly right.  

I put on feathers and shoot the dang things, just like we have been doing for centuries.  I shoot them into a sand bank maybe 40 or 50 yards away and watch the flight.  If they fly well (most do) then they go into the " to be used" pile.  
ChuckC

Where's this "Stu's calculator"?

I bareshaft with field points only and only use BH's on fletched arrows.

Tom, here's a link to the calculator
http://www.heilakka.com/stumiller/

I've been doing some cutting and making some adjustments.  I'll post and update tonight.

Unless you are nowhere near anyone or anything valuable do not broadhead tune with bare shafts!  I have heard plenty of horror stories and seen a few mishaps.  An unfletched broadhead tipped arrow can fly way off course and do some serious damage.

Bareshaft to fletched tuning is only the first step in the tuning process.  Fletched field point to fletched broadhead tuning comes next.  With fine tuning at the end.  

If the first step ends up being a bust that normally means your equipment ( arrow spine ) or tuning are the problems.  It just means you need to change something to find the right arrows and tune for the bow.

too much knowledge here for me to sound smart so i won't try lol i have spent lot's of time bareshafting to mixes results so now i just use them as a starting point to check for weak or stiff shaft and then fine tune with fletched arrows,what i have found is if you shoot your broadhead shafts ay say 30 yds they will show stiff or weak and then tune your set up off that!

arrows that fly right on at 20 yds will fool you shoot them at 30 to 40 yds and they will tell on themselves in a hurry!

I've never been able to get consistent enough results with bareshafting to justify the time spent.  I just put on the broadheads I want to shoot and use minimal fletching.  If they shoot the same as field points out to 30 or so yards, that seems to work well for me.  I figure if the Ace 200 grain heads shoot well with (3) 4 inch feathers they're stable enough for me.  I've shot them with (3) 3 inch feathers, but a sloppy release makes them do funny things sometimes.

I have tried bareshafting. It didn't seem to produce any specifically interesting results for me. Now I don't do it and still am able to hit targets just fine with my bow and arrows.

Whew!  Glad to hear ya had feather on with those broadheads. There is no way to get consistent results if the only drag on an arrow shaft is out front.

I'd be interested to see what you find today.  I know there is no way I could maintain good enough form to evaluate arrow flight for five hours!

I bareshafted my beman bone collectors, and had them right where i wanted, i then fletched them and they behaved stiff, so i turned down my helical and they moved back to the right (right hand shooter). My point is fletching will stiffen an arrow a bit, so maybe thats what youll have to try maybe more helical. I was even shooting 4" but they had too much helical, with a well tuned arrow youll be amazed how little helical you need, i see theese arrows with 5" crazy helical and i see a waste of energy. the quicker your arrow recover the more energy youll have at your target, anyone can have lots of speed through the chrono 3 feet from it but check the speed at 20yards aswell and compare. - sorry for being off subject just some of my pondering.
Tommy

Problem solved!!  Well I was using some 4" shield cut 4 fletch that I chopped from full length AMG feathers.  I've always noticed that the base of the AMG feathers were a lot thicker than my TF feathers but never really worried about it.  Seems a combo of the thicker bases with the 4-fletch configuration and a little too much glue that got onto the front end of the feathers making them stiff was causing a tail left off the shelf, and with the big 1 1/2" broadhead on the front the arrow couldn't recover at the short 15 - 20yds I was shooting.  So I used some TF feathers fletched up in the 4" 3-fletch, and 4" 4-fletch configurations and flight was perfect out to 25yds which is as far as I can go right now since I'm standing in the street shooting into my garage.  I was getting better flight with the 3-fletch configuration though because even with the TF feathers the 4-fletch had a very slight tail left off the shelf.

I was a little worried because I cut a bunch of my 30" shafts to 29" but thank the Lord they still fly well.

The fletch type and size will matter I think.  Any contact is an issue.  I believe that the reason you see people who say they need anything from a few inches out of the group weak all the way to a stuff shaft bare shafting has a lot to do with what they are using on the back side.  Often that doesn't get expressed.  3 or 4 feathers, 4"-5 1/2", straight, off set, helical, and parabolic or shield.  There is a big difference.