I am looking for opinions on fitting a set-screw type gas block.  I have an 18" SPR barrel and need to get the gas block on.  What do you guys use to get the gas block honed out (without overdoing it) and how tight should it be when it gets up against the collar?  I am hoping to do this once so I don't have to spend more money.    

Thanks

"Honed out?"

Are you saying that it is so tight that it wont slide onto the bbl?

It is an SPR contour barrel.  So it makes it up a couple of steps of the barrel but it hits a stop about an 1 1/2".  Not sure if I need to get rough with it or not, but I thought I would ask the experts first.  

Post a pic if you can.

You should not have to hone anything.

I have that same gas block on an 18" WOA SPR barrel.  I was warned before buying it that the GB would be so tight I would likely mess up any coating that was added to the barrel.  I chose to keep the barrel stainless so that wasn't an issue for me.  It was much tighter than I expected, but works perfectly.

[stupid]  might be possible to loosen the screws, place thin washers cut in half as spacers to slide on, then remove those if you don't have any other tools and are concerned about the finish [/stupid]
- I have no idea if it would work for this, I've only ever done this on applications that weren't nearly as important or valuable.

You could try heating the GB in the oven to 400-450*F and it should slip right on; it's an old automotive trick for interference fit parts, so you don't have to use a torch.  It might mean that you have to cut it off later on if you ever want to remove it.

Another option is to simply buy a ball hone and run it through a few times (you use a ball hone in a hand drill) until it has a tight slip fit.

You could also use emery cloth wrapped around a rag, and spin it in the GB by hand.  That might take longer than a hone, but it'd be just as effective, and cheaper than buying a tool you don't already have.

Is your barrel a stainless that has been painted or coated? That can cause a problem if the coating is too thick.

Heating as suggested will help if it is a few tenths too tight.  

If you really need to remove material and don't have access to a hone or machine shop equipment then you can use a dowel, then saw a slot  down the length if it in the center of the dowel. You can wrap some sand paper through the slot then enough wraps of paper to get it close to the inside diameter of the hole. Chuck it up in a drill to hone it out. Be careful as it can and will oversize it quickly.
Doing it by hand will work but take some time. Power tools are great but make it way too easy to screw up things if you don't pay attention.