Ha.
Well, I've loaded about 30K pistol rounds and have not had any squibs. I'm paranoid about it, maybe that helps. I've had duds, but no squibs.
I shoot a lot of revolver so squibs are particularly dangerous to me. In a semi-auto, a squib won't cycle the action, so you have a reason to pause and reflect while you clear the jam. A revolver, you just squeeze the trigger again and you launch another bullet, possibly into the back of the first.
Here are some thoughts.
1) I won't run with the powder hopper less than half full. Less powder means less force available to make sure the powder drops.
2) I clean the inside of the powder system with q tips and acetone or some other VOC to completely remove any trace of oil from the powder's path.
3) On my Dillon 650s, where I'm really making stuff fast, I have a Dillon powder check.
4) Even on the 650s, I don't actually go that fast. My cyclic rate is maybe 500 rounds per hour. Actual output when you figure in digging .380s off the shell plate and loading primers is closer to 400 rounds per hour.
5) Nothing beats eyeballing the round. When I load AA5 into 9mm to make hotter loads its easy to see the powder and impossible to double charge because it fills more than half of the 9mm shell. When I load only 4 gr of Clays into a .45, its difficult to see the powder and you would not recognize a double charge. So I also use a mirror and a light on the press to facilitate looking into each shell.
6) Know your limitations. I am a bit ADD, so I limit myself to 300 rounds without a pause. Then I go upstairs and fill primer tubes. Also for me I keep a "sterile cockpit". No radio, no TV, no other stuff.
7) on my turret, I do use an auto powder drop. Its a lee drop. The key with lee disk drops is to make sure that things are adjusted so that when the handle is at the botom of the stroke, the hole in the disk is directly under the bore of the hopper and riser. If its not, you could have problems. Particularly when
1) Its a large grain powder, like Clays
2) Its a small sized disk hole for light charges (like 2.9 gr of clays in .38 spc)
3) The hopper is not very full.
4) The insides of the lee parts have not been fully cleansed of oil and grease.
8) Thoroughly QC your loaded ammo. This won't help with a squib directly. But the better you know how "good " ammo looks and feels, the better you can avoid a squib. for example, I can tell if a .223 has powder because when I shake it, I can feel the powder move back and forth.
You can also tell if a rifle cartridge has powder because the powder weighs so much.
For example. A .45 may have a 200 gr bullet and use 4 gr of powder. So the powder makes up a tiny portion of the total cartridge weight. Unless you are confident in the consistency of your cases and bullets, you couldn't confirm the presence of powder by weighing the cartridge.
However, lets compare this with a .223 cartridge. In that case, the powder may be 25 gr and the bullet may be 55 gr. Wow. In this case it is EASY to weigh a complete cartridge and tell if its got powder. Especially since most .223 bullets are within .2 gr of each other.
When in doubt, weigh it. If still in doubt, take it apart.
I hope this helps. I know its only a matter of time before i get one, but I'll do my best to avoid one.
Don