Generally, factory is very consistant since they are starting off with new materials. there are several factors that can help keep the consistancy up. first use a quality loader that thoughs the same weight of powder each time. A P-W loader with rack and pinion type of powder and shot movement is the best. I do a lot of weighing out of loads on a scale for my hunting loads since I want the best out there. I can consistantly have higher percentage of shot in a 30" circle on than any factory. I load all types and gauges. Take some time to find out want your gun patterns best on even with factory loads.

I can see a variance of +/- 0.5 gains in loads with a sizemaster in the way you push the bar across. The Mec 9000 would be a good choice and if you can afford the P-W 800 B or elite that much better. I pattern more than 300 shells a year from trap loads, lead hunting and steel hunting loads. For tight and good patterns, look for low chamber pressures in lead loads. This is a "general rule of thumb" to keep with.

Trap shooting, you can reload a hull 15 to 20 times. Hunting, I would suggest only 3 to 5 times. More powder burns the inside of the hull resulting in wad sealing differences which result in variance in the the shell performance in velocity and pattern.

Get a good loader and use only the receips in the manuals.

To answer you original question, yes you can make some great loads, but you will also probably have a few bloopers.

My best investment was a powder baffle. Some of my buddies said some of my rounds sounded lighter than others. It was just a few dollars, and instantly cured the problem. Also, get the big shot tube.

And follow what these other guys are saying, cause they're all correct! Funnels, vaccum, slow down, etc. Pouring shot out of a 25 lbs bag is ridiculous, especially after you learn to pour it into a cup first and then into a funnel Also much easier to pour the powder from a cup than a big can of powder. You will screw up a few times starting out, and you might get to the point where you mess up and you need to throw out 3 or 4 shells since its progressive, but dont worry.