I've seen Henry repeating rifle ads (one is pretty entertaining), but I can't recall any ammo ads (maybe I should be watching another channel.)
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The Henry ads have been around for some time, Glen Beck on the Blaze is sponsored by Cheaper than Dirt, those are all that I am aware of.
On DirectTV the Pursuit, Sportsman, and Outdoor networks all have extensive hunting and fishing programming (nearly 24/7) and most of the ads are gums and ammo related.
Channels 604, 605 & 606.