anybody know anything about reactivating dessicant to use in ammo storage?

Typically it is reactivated in the oven at about 250 F for several hours(2-3).  

That only works if it's the correct type of dessicant material-some other materials may emit odd, even hazardous fumes.  Dessicant packs for military equipment typically have instructions on them for reactivating them, by the basic instructions bnz42 gave.  Just make sure you're doing this with a material that it works with.  There was a thread maybe a week and a half ago about what dessicant to use in your ammo storage, and there were some really good responses about what's what and what you can do with it.  Check that far back or more before you start heating stuff up.

I have two types sitting in front of me.
First is a 5 inch square brown paper bag. It has printed in it, "REACTIVATION TIME IN BAG 16 HOURS AT  245 degrees F"

The second is a 5.5x9.5x1.5 white paper bag. It has printed on it "DO NOT REACTIVATE BAG"

Both are manufactured by Sud-Chemie

Don't know if this helps or not. I throw one of the big ones in every ammo can (loose packed .45)

Quoted: I have two types sitting in front of me. First is a 5 inch square brown paper bag. It has printed in it, "REACTIVATION TIME IN BAG 16 HOURS AT  245 degrees F" The second is a 5.5x9.5x1.5 white paper bag. It has printed on it "DO NOT REACTIVATE BAG" Both are manufactured by Sud-Chemie Don't know if this helps or not. I throw one of the big ones in every ammo can (loose packed .45)

Dont remember seeing anything about instructions on the stuff I bought, its the Kraft bag clay dessicant.

I not a desiccant expert...but I do play one on TV.
Actually, I do work for Multisorb Technologies, one of the worldwide leaders in the design, development, production and marketing of high quality packaged and fabricated sorbents for controlling constrained environments ( Shameless Promo)
We make several style/types of absorbents that would be ideal for long term ammo storage...
There is alot of good info at www.multisorb.com

For reusable applications (gun safes and such) I recommend the DriCan www.multisorb.com/products/desiccants/index_html/cartridges/drican_html

For ammo storage I recommend www.multisorb.com/products/desiccants/index_html/bags/natrasorb_html

Here is some good info as well  www.multisorb.com/library/faq_html

As for re-activation, not all desiccants can be re-activated. I would advise contacting the manufacturer or replacing your current supply. Samples can be had from multisorb by following this link...
www.multisorb.com/samples/form_samples.cpt

Sorry if this sounds like an advertisment but there is no profit to be made on my part.
I am thier  Network Specialist and a satisfied consumer....besides, I get all the free desiccants that I want.

You can always use rice!  It works, too!  I have been using it in my salt shaker for years, but never thought about using it as a dessicant.  It's cheap, it works, it's easy to handle, it works, and it's safe for everything.  Did I mention it works?