In this case I'm not speaking of loads that are a few grains under normal levels but those loads that feature small charges of fast burning powders such as are frequently used with cast bullets.
Now, I don't think there is any problem with such loads in most cases. The problem arises when the loader inadvertently double charges one. A load of 17.5gr of unique in a 30/06 with a 180 if just fine but 35gr. is far from it. In most cases the loader insists that a double charge is unlikely because he is "very careful". Not careful enough though it seems.
I have seen a half dozen pistols blown up with double charges of Bullseye. Just recently I had a 30/06 Ruger come in with a jugged chamber. The load used by this shooter was the previously mentioned load of Unique.
In another case the shooter was loading 13 grains of the same powder behind a 485 grain bullet in a 45/70. This is a very mild load and is isued in thr trapdoor Springfields. In fact, in this case, he was shooting a mint conditioned original infantry rifle. The double charge ruined the rifle.
So if you are using loads where it is possible to easily double charge, be sure to include a visual inspection of the charged cases in your routine. Check them twice! If there is any question in your mind as to a charge, pour it out and weigh it.
I personally always use powders where a double charge will overfill the case. Everytime I spill some powder because of this I figure it saved me from a dumb mistake. Regards, Bill.

Bill,
Great post and great advice.
jeffe

Good advice. I almost got hit by part if a trap doors bbl when the shooter next to me fired a dud and then fired another into the plugged barrel. I saw the stock go past me but we never found the side of the barrel.

Imr's 4759 was developed to eliminate part of the double charging problem. A typical load will fill the case more than half way due to the powders designed in bulk.

That said I load 9.5 grs of Unique into the .45 Colt. You have to stand up and look into the cases.

Bill,
I used to load a lot of those ultra-light loadsin my Trapdoors.For the reason that you mentioned,I do much less now.
I use a dowell,with a reference mark cut with a knife,to check the powder levels in the cases.
Frank

I, also, have changed the powders I use for reduced loads. I used to use Unique and 2400 loads in my -06. Now I use H4895. Hogdon has posted some nice reduced loads for most HP rifles under a Youth heading on their web site.

I've never double charged a case, except on purpose to see what it looks like, but it's not a chance I want to take.

I shoot to relax, not for excitement.

Another good reason to visually inspect every charged case before seating the bullet.

A rack of 50 can be inspected in only a few seconds by placing the rack directly under a bright light source shining into the mouths. This is good not only for detecting double charges of fast powder, but also for detecting mischarges of slower powder such as you might get when the powder bridges in the measure.