Do you have the "flames" battery or the silver and red BRC battery?
The "flames" battery is an OK battery based on the last tests that I saw. But there is no guarantee that it is the same cell inside as the *fire brands have been known to use whatever is cheapest without regard to any bit of standard when it comes to consistent performance.
My personal view: I don't, and won't, run a *Fire in anything I own. The inconsistency is not worth saving a couple bucks when there are so many other, better, options out there. WillyB pointed me to a good battery with a a high quality Sanyo cell inside. For an unregulated mod, I haven't seen anything with a better discharge profile.
2 pcs XTAR 18700 Lithum Ion Rechargeable Protected Battery | eBay
It's in a jacket with flames and sparkles.
Would a magnesium battery be a safer choice? I hear they are less likely to explode.