Ads really need to be identified in order to be effective. A suggestion would be by adding something to the return address:
The easiest way to do this is TMA, 123 4th Street, Dept ML (for Muzzleloader) or 123 4th Street Dept MB (for Muzzle Blast), etc. Probably 25% of the people will not bother to put in the Dept. part, but the other 75% will.
For this to do any good, you will need to keep records on just how many responses you get from each source, how many dollars you get from each source, etc. From there you can expand your research by including a brief questionnaire with their new welcoming package, etc. You could find out their age, sex, marital status, degree of interest, flint or perc shooter, and the list goes on. An interesting demographic can be developed from the answers.
We did this several times with our customers, and generally, people don't mind giving basic information, especially if the questions are broad based. So, ask generally not what their income is but ask for 10,000-25,000; 25,000 - 50,000; 50,000 - 75,000 and so on. Or whatever. Ranges seem to work better than specifics.
A final thought on advertising. Placing an ad in a general interest sporting magazine is good for the bottom line of the publisher, but sucks for the advertiser. An ad in American Rifleman is wasted money for us. An ad in Muzzle Blasts is money much better spent. FWIW, I have had better success with the classified section than with display ads. The reason being is that people gloss over display ads but will read the classified ones. Why, i have no clue.
Finally, the best advertising is if you have someone who can place a written article in the magazine rather than a display advertisement. That costs nothing and is guaranteed to get results that a display ad won't.
OK, there you go, Advertising 101. Tomorrow there will be a brief test. Be prepared.
John