Actually, I just finished mine last night. You don't want to use the 6V light by the way. I popped two in a matter of seconds.
Moved up to a KPR118 7.2V light from Radio Shack and everything is working fine so far. I've heard that you can also use the Dewalt DW9023 9.6V light but my local Home Depot was out of those so I went with the Radio Shack one.
And, instead of using a 5/8" drill bit, you may want to use an 11/16", although I used the 5/8" and the batteries still fit, but they're tight.
The light is nice and bright, but I can't speak for battery/bulb life yet.
I bought one of these Garrity flashlights from Wally for $6
They had them in the impulse buy section by the registers, but they're probably in sporting goods too. After it took a beating (a few times) and kept working, I figured I'd give it a try as a weapon light, as it's brighter than any cheap light I've had before and fits perfectly in a 1" scope ring.
I haven't shot it yet, but it does a beautiful job of lighting my apartment where I point the rifle If it dies of recoil poisoning, I'm only out $6!
I have a similar one that I have abused multiple times, I like it since its LED and the battery life is good and I have abused mine over the bast 2 years something fierce. It hase dropped on my roof, fallen onto the road from my motorcycle at 35 and just generaly beatings along with some water and it keeps on truckin.
I just saw the same light I use as a tactical light on a Hi-Point 995 in a post on HPFF and he claims he's been shooting it like that a while. While 9mm carbine recoil isn't the same as 7.62x39 recoil, I'm hopeful as my Bubtical is a soft shooting beast.
Im an armed guard that works the nite shift and the light that I carry is the streamlight stinger its full rechargable and works great and is super bright. I bought mine at a trade show in vegas from streamlight at wholesale price for $50 with both the piggy back charger extra battery and car charger. I think that its a great light. http://www.streamlight.com/product/product.aspx?pid=7[/code]