DIY body boring?

I have a couple Angel-Fire A-1s - basically, cheap (but pretty decent) Surefire 3P clones. Only problem is that they are pretty much CR123A/16340 only; one will take a protected 16340 without any issues, or an unprotected 17xxx cell - but that is a very tight fit. For the other, even the protected 16340 is a very tight fit.

I'd like to use 18350 cells to get some more runtime and/or higher current handling. The wall thickness seems pretty generous. I've not actually checked this in relation to the depth of the o-ring channels yet, but at a glance, it looks like boring out the cylinder should be relatively risk free.

I wondered if anyone could recommend a reliable method to bore a Surefire style body from 16mm to 18mm without access to a lathe? I've heard of people using brake cylinder hones, but wondered if there were any other methods? Sand paper around a dowel would be another obvious option, but probably hard to keep that even.

If you are handy, have a good eye for detail and don't mind ruining the light, then a brake hone will work, but it takes some skill. Sandpaper will work, but it will take a long time and you are right, it's hard to keep it round instead of ovaling it out. If you can find a junk light or an old maglite or even a piece of tubing, you can test it out and see if it's for you.

I don't know about the standpoint of putting a different battery in the light, others here would know better. I don't use anything but NiMH batteries.

Thanks for your response.

I have dremmelled a 16mm tube to 18mm (most any brand rotary tool would work), using the conventional sanding drum(s) that those tools use. But it only works if you have the tool,which you probably don't, because if you did I'm sure you would have thought of this yourself.

I do have a rotary tool (not Dremel brand, but same sort of thing). I just don't think that I would make anything like a decent job of it with a Dremel sanding drum. There is no way that I would be able to keep the bore cylindrical.

Pilot reamer. Not cheap but have made my own for shotgun choke tube installs. Use pistol drill and a vise.