301 or 302 for tracking?

[jtara]

I use Adwords to send traffic to a merchant. Currently, my destination URLs and display URLs both go directly to the merchant.

Unfortunately, this gives me no visibility of search terms, content sites, etc.

I want to set-up my own tracking site. (Don't want to use Google Analytics or a third-party tracking site.) I will set the destintion URL to my tracking site, and the tracking site will redirect to the merchant.

Which is the appropriate redirect? 301 or 302?

My concern with 301 is that web browsers may cache the redirect and cause subsequent clicks to go directly to the merchant, without being tracked. With a 302, a correctly-written browser will ALWAYS go to my site.

True or false? Or, in practice, will all current browsers always re-visit my tracking site?

Or completely a non-issue, since subsequent clicks could only be on the original Google link as it appeared on the SERP or on a content site?

[jtara]

OK, I'll answer my own question.

Decided to ask another question: "what would Google do?"

So, I used the Firefox extension, "live HTTP headers" to answer that.

Google does a 302. Also, checked the tracking service used by a popular office-supply store for their ads: also a 302.