What tool are you using to taper your fir shafts?  
I have used the tru-center taper tool on cedars for the past 20 years with no problems.  I just put nock tapers on a dozen Shurwoods, and they look like crap. I even put a new blade in the taper tool.

I use my Woodchuck for all my woods.That sometimes happens when tapering a hardwood shaft.I prefer the sanding with the Woodchuck.

I just did a dozen douglas fir, on the bench sander with the taper block in place. quite similar to the woodchuck.....

The fibers of the wood in Fir is different. Hand held taper tools work but sanding is better. Just clean them up with some sand paper by hand and they'll be fine.

I do what Matt does. Also take it a bit slower, you'll still get the split though on some.

Like Ryan said go slow. They can split. I use my disc sander and if you have one get a taper block. Much cleaner grind.

WOODCHUCK!!!!!!!!!!!
For ALL wood and consistent tapers.

Taper block on a sander.  I'm no woodie pro, but I only build with fir.  I'm afraid I'll be disappointed with other woods.

If you've got a table saw or a disc sander either one you can make a very simple jig that will allow you to make perfect tapers.  As with all power tools, please be careful if you try this.

try the bearpaw taper tool from kustom king....that has worked well for me, but you will still need to use a new blade about every four dozen arrows......

Woodchuck is all I use. Works great on all woods.

Another vote for Woodchuck.  Excellent tool.

I have a taper jig set up on a disk sander too.  I have never got tapers on fir from a hand held taper tool that made me happy.

Mine get chewed with the hand held pencil sharpener type also, just some 120 grit sanding and they are fine.

Woodchuck or some kind of disk sander with a jig.

I just use a cheap $60 belt/disc sander, you can use the belt to put a rear shaft taper on too.

Eric