I do know that it was a long fight. I moved to Iowa almost four years ago, and the first year I was here there was an NFA bill (would have allowed all NFA items to legal), which I was happy to contact those who represent me and request their support for. Unfortunately, it didn't get much traction anywhere in legislation.
The remaining three sessions, the bill was changed to allow only suppressors. The first year the House passed a version, but the Senate didn't allow it to come to a vote. Last year, the Senate passed a version but the House stripped it of its language and substituted an Omnibus pro-gun bill (which addressed many failings in current Iowa law such as not allowing us to teach anyone 13 and under to properly handle a handgun), which also didn't come to a vote in the Senate.
This year, I believe that two pro-gun bills have passed. The silencer bill, and a bill that allows anyone with a CCW to carry while riding an ATV.
There are a couple of different Pro-Gun groups in Iowa that lobby for different bills each year. Each sends out e-mails to anyone who's signed up giving updates on how the legislative session is progressing and letting us know who to call and e-mail regarding the legislation. I'm happy to say that both my Republican Representative AND my Democrat Senator voted yes for the bills. So maybe all of the e-mails made a difference. I know that I tried to spread the word to all sympathetic family members here and to the few "gun guys" where I work. That probably didn't hurt either.
I'm just glad to be finally able to get my silencer from MI (where its properly stored per NFA regs), and get started on some paperwork to add to my collection.