First of all, I began reloading clear back in 1972 or so, with a .38 special Lee loader. Since that time, I've advanced "a bit" to RCBS equipment, interspersed with Hollywood, Pacific, etc. etc. In other words, I pretty much know what I'm doing.
Pretty much.
I've been playing with a load for my SKS, consisting of Lee's 155 grain boolit over 22 grains of 4895. It operates the gun quite nicely and deposits the brass within easy reach. Accuracy is becoming quite good, with an occasional flyer, as I experiment with seating depths, etc. Today I finally set up my chronograph and began noting the velocities.
They were all over the place, from a low of 1192 fps up to 1530 fps. What? I returned home and reviewed my loading sequence. I've been using Lee's 1.6cc scoop for charging, since I'm only loading a few rounds at a time for testing. I got the scoop out along with my scale and began throwing charges in my usual fashion. To my astonishment, they varied as much as .7, or over half a grain on the HEAVY side! Then I realized the obvious.......I was scooping the powder, then tapping the edge of the scoop with my finger to "level" the powder. There was the answer. My tapping was causing the powder to settle while the excess was falling back into the charge cup . I finally used a business card to scrape the top of the scoop (as Lee suggests) and suddenly the charge variance was less than .2 of a grain.
That explains the fliers AND the wild velocity differences. Moral of story? Follow the manufacturer's directions......they seem to know what they're talking about! By the way, I set up my Uniflow for future use..................ahem.