When fly fishing for freshwater big game species, a bite guard is necessary to keep from losing your fly to toothy critters. Pike tend to bite a fly at the head, and that causes me to believe that's why there are more bite offs, than say with a walleye; I can't vouch for the muskies since I haven’t caught one on a fly yet. The main choices for a bite guard consist of a large diameter “shock tippet” usually around a 150 lb test hard monofilament line, or wire coated line. I will be refraining from using the mono shock tippets for pike. Even with 150 lb test mono, I've heard anglers report bite-offs. I've yet to hear a report of a pike biting off a wire tippet. With the availability of cheap tieable wire nowadays, it leaves me little incentive to use monster diameter saltwater line. I use 49 strand (19 will also work) coated wire as the bite guard. It ties as easy as mono and is simple and quick to use.
I usually am fishing a sinking tip line, so I tie leaders with fluorocarbon. I have been using about a 3-4’ butt section of 20lb fluorocarbon line connected to a 12-18" wire bite guard with a surgeons knot. This year I am going to get a little bit heavier butt section and use 50 or 60 lb fluorocarbon line, tie on the 20 lb fluorocarbon tippet, and then tie on a 12" wire bite guard ("shock tippet"). This setup should be IGFA kosher. Hopefully I will get a little bit better turn over on some of the larger flies I fish with.
One thing I may try this year instead of knotting the wire tippet to the fly, is to twist the wire and re-melt the plastic coating. I've heard from many other anglers that they've never had a line failure due to the melted coated coming apart. Some guys leave a larger loop tied on the other end of the tippet and pre-tie their flies to the wire tippet, and swap out the entire tippet section when switching flies. I'll also be tying up similar leaders using monofilament for my floating lines. I've had good success using the Berkley big game mono for leader sections, plus it’s cheap and readily available.
Here's the bottom line: finding materials for pike leaders can be difficult if your looking for fly oriented brands like Rio, Climax, SA, Maxima. I've had really good luck using Berkley Vanish fluorocarbon and Beadalon 49 strand bead stringing wire. Try to find anything larger than 40 lb test Rio fluoroflex or hard mono, frog hair, or Maxima big game leader spools in stores in the metro. I couldn't. I went to several different fly shops and a big box store and they didn't have them. The big box stores had vanish leader spools, though, from 10lb through 100 lb. Beadalon you can find at just about any craft store.
Yeah, some of those other lines may seem to be nicer to use, but I'll stick to using what I can readily get at the store, and it seems to do the job just fine.