The biggest thing I have found to tighten up ES is with finding the powder "node". Primers can also tighten up velocities, as stated above. I have experienced primers helping fist hand. My custom .308 Norma had extreme spreads in the 30-40fps area for 5 shots. I switched from Winchester magnum primers to Federal 215s and my ES shrunk to 12-19 FPS after testing multiple times with 5 shots each.
As others said though, you have to have an accurate way of measuring powder. I use a Bald Eagle digital scale. I'm not sure if they make them anymore or not. We also have a RCBS beam scale, my Dad prefers it. Both scales will read the same powder charge equally. Meaning if the Bald Eagle measures 45.0 grains, so does the RCBS. The RCBS Charge Masters or any other powder measure works great to dump the majority of the powder, but I highly recommend trickling the last few tenths on a scale and double checking it.
I would get a beam scale, preferably an RCBS, and use that to trickle with after throwing the charges on your Charge Master. When you have that, then I would work on finding the powder node. Do this by loading one round each in 0.2gr increments from a few grains under max, up to max. This will show what charge weights produce similar velocities. For example, 90.0 grains goes 3010, 90.2 does 3020, and 90.4 does 3012. If you load 5 up at 90.2, using an accurate scale, I will bet the ES will be under 30fps, probably closer to 20 or under with the right primer. This is just a pretend example, but that's what you're looking for when finding a powder node.
I use a MagnetoSpeed sporter, they're around $160. It's far far better than the old Pro Chrony we use to have. It does affect group sizes and point of impact on my rifles, but I just focus on finding a powder node and then I shoot groups to find the sweet spot for seating depth. Once I find a good shooting load, I'll retest it over the chrono to verify it. This is the method we have been using lately, and it works great and is the most affective and efficient method I have tried.