There are more than three hundred million guns in people's hands in the US. With every massacre, more people rush out and buy more guns, right or wrong.

What government authority could even begin to confiscate so many weapons ?

The horse has bolted.

Joe

Bugsy

"So are these all registered and legally owned firearms Is Mise?"

Yes, the thousands of illegal ones are another issue.

"Are there as many semi-automatics or automatic weapons as previously?"
There are no legally owned automatics, except for minuscule special exemptions; there are less semi-autos but many thousands of repeating rifles that are faster than many semi-automatic ones.
There are now more semi-auto pistols, at a guess.

"I would hazard to guess that the vast majority of these weapons were purchased legally, by people who are members of gun clubs and have had the requisite background checks."

100% legal purchases and ditto on background checks, only the better class of citizen can have a firearms licence.

"The fact that 'gun' (generalised) ownership has increased under our laws and yet crime hasn't risen, indicates to me that our guns laws are working and shouldn't be changed or relaxed."

Port Arthur was but a blip on the continuing downward trend in gun and other crime.
It is worth noting that Australia's second worst massacre, or mass killing, was done with a .22rf single shot rifle and a rubber mallet
(Clifford Bartholomeu, 10 murdered, 1971 in South Aust.).

Port Arthur is also notable for the left-handed Bryant pulling off feats of marksmanship firing right handed, or so some reports by witnesses say.

So, Is Mise, you would certainly disagree with American organisations like the NRA and some Republicans that believe that crime rates increased after the introduction of our current gun laws?

It appears that some people in the pro-gun group are under the apprehension that people who support the current firearms laws think that they are just all gun nuts and the laws should be tightened. Not at all. I think that for the most part legal gun ownership is being kept well regulated and in the hands of responsible people. That is, they are working.

I just don't think that they need to be loosened for your convenience.

The second worst massacre in Oz was by diesel fire bomb and killed 15 patrons and staff of the Whiskey Au Go Go nightclub in Brisbane, 1973. One could also list the loss of lives and assets from deliberately lit bushfires.

It only took 2X23 litre cans containing diesel and it could have been less. Had petrol been used, the explosion and enormous heat would have resulted in no survivors from the 100 present.

An offender has many options apart from the noisy firearm that betrays their crime, usually results in witnesses to their escape, retains fingerprints and DNA and is difficult to dispose of.

As long as the callous, irresponsible, audience-hunting media sensationalise the crime and give the offender enormous publicity then and forever later (as the do with Bryant), would-be offenders will use the firearm, or bomb, whatever they see as the gold standard for media attention and worldwide notoriety.

However the likelihood of becoming a victim of a mass homicide by firearm in the US is probably far less than that of being hit by lightning.

//However the likelihood of becoming a victim of a mass homicide by firearm in the US is probably far less than that of being hit by lightning.//

It isn't. The National Oceanic & Atmospheric Administration give an average figure of approx. 500 lightning strikes per year, with 9-10% of those resulting in fatalities. There were 372 mass shootings in the US in 2015, killing 475 people and wounding 1,870, according to the Mass Shooting Tracker, which catalogues such incidents. In other words, you're almost ten times more likely to be killed in a mass shooting than you are to be killed lightning if you have the misfortune to live in the States.

https://en.wikipedia.org/wiki/Lightning_strike
http://www.shootingtracker.com/Main_Page

When you stop to think about it, it's quite weird that mass shooting kill more people than lightning. We don't know how to prevent lightning strikes, whereas we have a much better idea of how to prevent mass shootings: limit access to firearms. It's difficult to carry out a mass shooting with a slingshot. The fact that the mortality rate for mass shootings is nearly ten times that of lightning strikes, when it should be much lower, is testament to how ridiculous America's gun laws are.

When you want to make stupid comparisons with numbers that are easily available onthebeach, FFS at least make a 5 minute effort to look them up.

US deaths at mass shootings in 2015: 475

http://www.bbc.com/news/world-us-canada-34996604

US lightning deaths in 2015: 26

http://www.lightningsafety.noaa.gov/fatalities.shtml

The number of school shooting incidents alone (not deaths), was 64!

Now if you want to say a 'victim' of either homicide was either shot but not necessarily dead, then we can look at the stats again:

Number of wounded in mass shootings in the US 2015: 1870 (reference given above)

Number of people struck by lightning in the USA each year: an estimated 330/year on average (2004-2013 period)
http://www.lightningsafety.noaa.gov/odds.shtml

If you broaden the definition of 'victim' to include those families and friends psychologically traumatised by mass shootings, then that number will again be far higher.

At least try and pretend that you have some empathy.