Here's how it went down last year:
The DNR, after 8 years of pistol caliber rifles without a single accident (we've had several slug gun shootings in that time), decided to propose any rifle .243" or larger for deer. Some say that the proposal was due to hunter petitions, which is a moot point anyway, as the DNR only advances proposals that it wants to the public comment phase. Just last month at its meeting, it turned down two citizen petitions and advanced one (baiting). The DNR stated in writing last year that after examining the issue, it determined that rifles posed no safety issues, nor any adverse effects on the herd. It defined the rifle proposal as a social issue only. Public comment was pretty evenly split amongst proponents and opponents. The Natural Resources Commission (NRC), which is comprised of unelected members who do not answer to the general public, recommended that the DNR not pass the proposal. The DNR then simply pulled the issue without rejecting it, with the intent of studying the issue more.
Fast forward to this year. State Representative Arnold introduced H.B. 1231. It has been said that he had a petition in his possession with over 1100 pro-rifle signatures, along with the personal desire to hunt deer with rifles himself. I've heard that Rep. Arnold has close ties with the DNR, and even does legislative work for them. Supposedly the DNR coached this bill along. I, however, cannot substantiate any of that. Then the NRA got involved, and the deal was sealed. 122-17 was the total vote of both chambers.