An accurate, sharp, big game broadhead shot from your bow is essential. Years back, when I was shooting new arrows out of my compound, I would paper tune the shafts with and without fletching. Then tune with broadheads with the intended fletching.
I’ve always liked feathers on my arrows as they are more forgiving than vanes. The downside of feathers in the hunting woods is rain. They lay flat and no longer steer the broadhead well.
Today, many new bowhunters have bypassed paper tuning by going for mechanicals that fly like field points. It is a shortcut that can create a less informed archer about his/her equipment and more reliance on mechanicals to forgive poor bow tuning.
In my crossbow, vanes make more sense. I advocate spin to all arrows. It’s like rifling in a rifle. The spin creates stability, and allows rotating broadhead blades from steering the short crossbow arrow. I like offset vanes. A slight helical may work too. Experiment! Experiment! Experiment!
When all your tweaking comes together you should have some understanding of your setup and limitations. As for me, my crossbow limitations with fixed blade heads end at 25 yards. I like muzzy 1 1/8 3 and 4 blade heads.
Big blades tend to plane, avoid them.
Accordingly, for me, a mechanical head like the Swhacker 125g 231 is a great choice for longer and accurate shots provided you have the delivered KE and lethality for the shot and shot angle.
One thing you may want in your bag of tuning tricks are brass arrow washers to add some weight to a broadhead or a field point. Three Rivers sells them. They are 5 grains each.
Good Hunting!
