RCR123'sor a 17670 in an Elzetta

Just wondering what kind of batteries I should go with for my Elzetta? Will a 17670 give me a higher run time then a set of RCR123's? I already use CR123's and RCR123's but was considering switching batteries for this light.

RCR123 batteries are usually rated at 750mah. Chances are they will be somewhat less than that in real use.
2xRCR123 will give you at least enough voltage to keep your Malkoff M60 in regulation.
These batteries are short on run time.

The 17670 is rated at 1400-1600mah typically. I don't know if they actually run short of that in real use, or not, because I don't use them.
I'm not sure if the 3.7v of this battery will keep the Malkoff M60 in regulation for long. It may drop out of regulation very early.
This battery is short on voltage for best operation. You will get good runtime, but likely to drop out of regulation early.

As for the pair of primary CR123 batteries,they have enough voltage to keep the light in regulation, and also give 1500mah capacity to run as long as the 17670 or longer.
These batteries are the best for the combination of both run time and voltage regulation.
But, they are not rechargeable.

I personally only use primary CR123 batteries in my Elzetta.
I buy them online at prices between $1-$2 each, instead of the huge prices that are seen at department stores.
This keeps the battery cost to a level that won't make you broke.

I am under the impression that the 17670 will do fine in the Elzetta. The Malkoff M61 drop ins have a voltage range of 3.4-9 volts, li-ion batteries are 4.2 volts fully charged and 3.6 volts nominal. I am not a battery guy but I think the 17670 will perform fine... if it doesn't I won't be buying an Elzetta.

17670s work pretty well with the M61...I use them, as well as 2xRCR123s in my C2, 6P, VME Twisty, with M61/M60 variants, and the RCR123s are a bit brighter, but have a lot shorter runtime, compared with the 17670. The thing that makes the 17670s better in my eyes, is the loooonnng slide in brightness once it falls out of regulation, giving you plenty of time to switch batteries at your leisure ...while the RCR123s will just shut the light off once one of the cells reaches it's low voltage protection point, leaving you in the dark.

Thanks for the replies. I'll be running an M60 for now but I'm assuming the same things apply from the m61 minus some run time on the m60. Im going to run rechargeable cr123s at home and just regular cr123s with backups when I'm camping. I'm guess that maybe my best option.

The specifications for the M60 show that it is regulated from 3.8v - 9v.
The 17670 at full charge is 4.2v, and it will run in regulation until it gets down to 3.8v, and then drop out of regulation until the battery depletes down to where you should recharge.

So, it will run for a while before it drops out of regulation. I don't have a time figure for how long it will run before it drops out of regulation.
The module will run on that battery. I think it would run better at a higher voltage, but you can use it.