Does spar varnish work well on arrows where target burn is concerned?
I have tried Deft, but it is not very glossy or resistant to burn.

I use it, since I already have a dip tube assembly done up for rodmaking and it's filled w/ spar varnish for those. I see a bit of target burn, but not as bad as one would think. My varnish is thinned 40% and is at 80* when I dip.

Another alternative is to thin it 50/50 and use a large syringe or turkey baster and flood a coat over the shaft. Once it's almost stopped dripping, hang it overnight and it's ready to go. I like to steel wool the finish lightly, for a satin finish.

Okay, you brought up a couple of questions for me. First does it have to be thinned and second I am guessing by your description that you can brush this stuff on?

It doesn't have to be thinned, but you get a more even finish thinning it. It also penetrates better thinned, so even if you have a target arrow that's got a bit of burn, the wood is sealed against moisture.

Yeah, you could brush it, again if it was thinned it would brush better, eliminating more brush marks. But I say get a cheap throw away baster, a paint roller pan liner to catch the drippings, and just flood it with a thinned coat. It's the easiest way to get a varnish coat that you'll like the look of, IMO. I used the same method on bamboo rods for 5 years, with great results. Just hang a string with a small spring clamp or alligator clip attached, clip the shaft by the point end, and flood a coat over the shaft, when it's almost finished dripping, use a latex glove and switch out the shaft for another. Let dry 24 hours or more, and decide if you want another coat. If you do, lightly steel wool the shaft to give it some "tooth" and repeat.

Great thing about spar varnish is it's flexibility. It was designed to bend with the wood and not crack.

Thinning it should help as a thin coat will set up harder than a thick coat.  Part of the issue of burning tho, is being a "spar" varnish.  Spars are formulated to have some flexibility to them and are a softer finish, which gives them a much greater tendency to target burn.

Yep, Fletcher is right. They will burn a bit, but are easy to touch up. My everyday target/stumping arrows get the burned area lightly sanded and a coat of thinned spar wiped on when they get to looking too bad. It's not the best coating for an arrow, but I have everything all set up for spar varnish, so I use it. I like the gasket lacquer squeegee things, but they cost money, and I'd prefer to spend on other things.