What length of bolt for my crossbow?

I'm new to using a crossbow and just bought a Wicked Ridge Invader X4. It was supposed to come with 3 aluminum bolts, but it didn't. Thought I would their length. The manual recommends 20 and 22 inch bolts. Is this just based on preference. 20's I imagine are lighter and quicker? 22's a bit heavier but better penetration? Going to buy some carbon ones tomorrow. Also, are mechanical broadheads different for crossbows, or any broadhead will work?

I have always used 20" aluminum bolts with a scope. What's your draw length? 20 or 22 will both work well. But for you can't say anything without knowing whether you use scopes.

I also agree with the 20" length carbon just make sure the nock is correct for your bow. With the speed your xbow shoots, I would personally use the specialized mechanical broad heads designed to not pre-maturely open due to fast velocities created. I once watched a youtube video and 5 out of 6 "crossbow" broad heads would open before hitting the target. Swhacker or nothing for me.

I use 20" aluminum bolts with my Wicked Ridge with the new Spitfire 4 blade mechanical broadhead. A very deadly combination!!

What's your draw lenght?

Either 20 or 22 will work. I have always used 20 inch so they dont stick as far out in the quiver when mounted onto bow and in the bow when ready to shoot. And you can use regular broadheads for regular bows or the special crossbow broadheads. I have used both and not sure there is any difference other than they seem to paint the special labeled crossbow heads are orange in the muzzys and the rages. 

I do use carbon arrows too also. See no reason to use aluminum anymore and deal with bent arrows when carbons are so nice. 

Good question! My gut tells me longer arrow but not sure what science says? Back 10 years ago when you had to “earn” your crossbow I worked with a guy shooting 26” arrows and scored on 2 Adams County Giants so they worked for him but I’m curious to learn about this topic? I’m a vertical guy at heart but I do have a couple spots that just set up better for a crossbow situation!