Keep an eye on your valve and make sure its not leaking. Sometimes you have to take the measure apart and clean the valve as they start to "Drizzle" on the cheaper ones. An easy test is if the nose is empty, take a white piece of paper towel and lightly tap the nose on it. If the valve is solid, there should not be any power on the towel.

I have a number of those kind of loading flasks, 20, 30, and the big one is a 50. My cheaper ones will Drizzle from time to time and have to be cleaned so they tighten up. (you can also tell when you have one in your pocket and when you reach in, your pocket has powder in it)

But I load my black powder revolvers out of them. And I carry the 50 for hunting when I want to throw two charges in a gun to reload.

I will say, its not recommended, I know that. But I do it. That is not to mean you should.