A good letter but not likely to actually be read. The thing is that a legislator's staff reads the letters and really only to tally the "fors" and "againsts." A simple, "I oppose [identify the legislation] as bad policy" or "I support [identify the legislation] as good public policy" will usually be sufficient. What legislators are really looking for is a count of how many people are on each side of an issue.
You can add a bit more argument if you like. But you want to keep it short and be very clear about what side of what question you're on.
Our lobbyists are the ones the legislators listen to for argument -- assuming that they've been able to conclude that there's enough support for that side of the question to warrant paying attention.
"It is long been a principle of ours that one is no more armed because he has possession of a firearm than he is a musician because he owns a piano. There is no point in having a gun if you are not capable of using it skillfully." -- Jeff Cooper