From that article, "cut firearm suicides by 74%... no evidence of substitution of method of suicide in any state.
You're leaving out the "based on modeled statistical estimates" part, which means this isn't an actual reduction, it's a guess based on lots of assumptions.
The point was, the wikipedia article you cited did not support your claim, it showed that the numbers in Australia (where the baseline measurement was rather low to begin with) are poorly understood.
In addition, the argument that taking away someone's gun prevents them from committing suicide is a bad one. If I want to commit suicide, that is my right and you do not have a right to interfere with my choice.
Wierd. Right after the word "state." in the part you quoted, it said that it reduced homicides similarly. Guess you missed that.
FWIW, I agree with you on suicides. But it would be much safer for everyone around you if you could go to the pharmacy and purchase a cyanide cap, to be consumed only on the premises (so you didn't take it home to poison someone else). I'm thinking that, even if they had to provide a little annex for you to occupy and a free can of pop to wash it down, it would still be cheaper than a gun, and certainly less hazardous to those around you.
I don't know whether reducing the accessibility of guns reduces murders, it's entirely possible that if you sit down and think "I'm determined to kill Bill, but how?" you'll find a way, even if it's not as easy as a gun. But I'm pretty sure that it reduces homicides. I'd expect that it would reduce unplanned, spur-of-the-moment, and accidental killings, killings by small children, etc. by a lot.