I've heard a lot of people worried about double charging on reloads, and it can cause problems! There are two ways that I used to avoid this problem. First I to pick a powder that will fill 60% or more of the casing at the proper load. Second, if the load characteristics will not allow the first condition; I make a wooden dowel that will fit in the neck of the shell easily, and put a mark on it for the correct powder level. I also record the rifle the load is for , the powder type, the ballistic tip Style, and the load volume itself.
Here is the reason we reload:
My sister texted this to me so I have no idea where it came from, but it was too perfect not to share!
Now back to the reloading, the first condition makes double powder charges impossible; because if you double charge a case with a 60% or greater fill, the power runs out the top! This is an immediate indicator, and the powder is easily poured back in the dispenser where a single charge can be substituted for the double one. This is the best safety against double charges when reloading.
I also find in most cases, that the larger charge of powder Spike's a lower initial explosion pressure; that burns for a longer duration of time, resulting in an increase in velocity. This is not always the case but generally it does seem to hold true.
But sometimes this is not the most accurate load for the specific gun is going into, any faster burning smaller volume powder must be used achieve accuracy. In this instance, the lower fill volume forces the reloader to use the second method; complete with the marked dowel, to double-check fill levels. This can be done quite quickly, if the dowel is smaller by 1/3 or more Thunder projectile. I find a group of fuil brass is easy to check by this method, and this dowel n be saved with the reloading dies.
There is actually a distant third way of doing this oh, that I do not like; nor do I recommend it. You can weigh a filled brass casing, and use the weight that's a go no-go Gage. I don't care for this method although I've seen it used, because there are variations and the weight of brass casings from different manufacturers.
I feel that brass casing variations especially on a low-volume feel, could lead to a double charge; that the reloader would not catch! The first two methods described, work every time; and I've never had either one of these Miss a double charge problem....
Be blessed, and say safe