You're right. They're not the same. Pot smokers are incarcerated at much higher levels.
As for the rifle, you may be thinking of Olaffson's case, I think. There's no doubt that ATF has gone after a few gun owners and flat out fabricated evidence to suit themselves. It doesn't change the numbers.
Well, I'll agree with you on the numbers.
There are more people in prison due to drugs (pot) than there are due to gun crimes.
That is probably right in line with the number of people that are partaking in said illegal activity.
People selling drugs are probably 100 to 1 with people selling/possessing illegal weapons.
The penalties for each are different however.