Ok, I'll start by saying I know nothing at all about carbon arrows. I shot Alum and Fiberglass back in the '70s, but have shot nothing but wood since about 1980. Well a friend of mine gave me a couple of Dz old carbon shafts, some fletched some not. So I thought I would try to make them shoot. These are Cabelas Outfitter Series shafts, don't know who made 'em. They are marked 45-60# and are already cut to 27". I'm shooting them out of a longbow 62#@my 26 1/2" draw. Now here comes the confusion part. I tried to shoot a bare shaft at about 15yds and that arrow nearly turned sideways nock to the right. I shoot Rt hand. That arrow would hit at least a foot to the left of my aim point. I done this several times with two different shafts and the results were the same. Now when I shot fletched arrows set up the same but with a 4" feather with a slight helical they would hit near POA, but fly slightly nock left. I'm so confused, and to make it worse I got almost identical results from one of my Bear takedowns....@45#!! Can I get enough tip weight to make these shoot?
What point weight are you shooting? Those will be stiff little buggers at 27". The 60# in the equation is at 28" I think, so cut to 27 you are going to need lots of weight up front especially if your longbow is not cut to center. The nock left for your fletched shafts is probably due to them hitting the riser and kicking left (kind of a false positive sort of thing).
Carbons can be great, and they can be frustrating. I finally found some I like (Beman ICS Bowhunter) and I'm sticking with them.
BTW: I think Carbon Express made at least some of Cabela's arrows.
These arrows have standard inserts and I was using 125gr points, only screw in points I could still find here at the house. I thought of trying a screw in broadhead adapter and a 160gr glue on field point. that would add about 75-80 gr of tipweight.
I'd do whatever I could to add tip weight. I don't know if 75-80 will be enough, but it's a place to start.
You will need 100 gr brass inserts just to get started, 27" is real short and they will be stiff.
Stiff indeed, don't know if it means the same or not, but when I put them on my spine tester for wood arrows they show a .325 deflection or in other words almost 75#. I'll order the brass inserts.
Brass inserts is a start, but you may need some more point weight also. You may want to get an assortment of weights to try. I know 3rivers has some packs of I think 2 each from 100-225 or so. They are very handy to have around, and you can try the heavy ones before you even put in the brass inserts to see what they do.
I am shooting an arrow close to that for spine at 29" with 245 up front. I am shooting at about 50# with a LB cut out about 1/8" from center if that helps.