I mark bullets with different colored sharpies. i also use combinations of colors. I have red, blue, green, yellow, orange, and black. I will do a full bright color, then a bright with black stripe (half and half) for a total of 10 colors.
Then I use the OCW load calculation method of finding my optimal charge weight for each round and have devised a spreadsheet for use with this method. you can download the spreadsheet here:
https://dl.dropbox.com/u/42863631/OCW%20Worksheet%201.2.xls
Enter the gun/and known load info on the top cells, most important is your MAX LOAD number for a given powder. I had intended to set these values with known caliber/powder/bullet weight database lookup, but with the variances in load books i don't want the liability. so load YOUR trusted value. I've left this filled in with my last trip to the range for you to see an example of a load for the .308WIN for my marlin.
The Load Variance dropdown will determine how finite your charge differences are. don't just load 3 bullets per load. this will not account for any flyers and bad called shots. Load a min of 5 per charge weight.
ALso, I load one extra bullet at the lowest weight "sight in round" to use as a cold bore/clean bore fouler shot.
This spreadsheet will also print targets with the charge weight printed on each target for all 9 loads and a convenient lid label that fits into a .308 MTM 50 round box.
The rounds are fired in this order - at a clean target, black 1" dot, at 100 yards. Some folks say OCW should be done at 200 yards but I disagree. 100 yards will not let light winds play havoc on the results as much as a longer distance shot will. Set your scope to be 1-2 inches LOW with the sight in group. So say your sight in group of 4 shots (fouler and 3 sight ins) ends up ON the dot, turn elevation down so future impacts will land about 1" lower than the bull.
Then place the rest of the targets up at the same time. You will have 9 sheets of paper stapled to the backstop. Fire one shot from each load, round robin (load 1, 2, 3, 4, 5, etc.) and then repeat with about 1-2 minutes between shots to allow the barrel to cool. BE CONSISTENT and patient with this. THis method condenses multiple trips to the range into a single afternoon, with 1 or two follow up trips to tweak the desired COL of your load.
YOU ARE NOT CONCERNED WITH GROUP SIZE AT THIS POINT. I cannot stress this enough. What you are looking for is a consistent average impact shift between loads, and you will use the load in the middle of the three that exhibit the LEAST impact shift from load to load.
So in my case, the three loads that landed closest to the same point on the paper (by average), were 45.2, 45.5 and 45.8 gr's of varget. I now use 45.5gr as my OCW or Optimal Charge Weight load. This takes into account of your barrel vibration and timing to use the load with the bullet exiting the barrel at a "time" of near rest or maximum stability of the barrel as it vibrates.
Now that you have your OCW, I want you to load 9 rounds at this charge weight, and print 3 1" black dot targets and fire the first three rounds at the first target. Throw this target away. the first shot will be cold bore...make sure you NOTE this in your log book for future use. the remaining two targets and 6 rounds, fire them round robin (alternate targets) with 1-2 mins between shots. and examine the resultant groups.
the shape of the group will usually tell you which way to move the bullet for future loadings. a triangular group indicates that you should start by moving the bullet out (longer) in .005" increments and continue fine tuning as your group size decreases. A stringing group (shots in a line) indicate that you shoudl bring the bullets in (shorter OAL) by the same amount. I might be reversed on this however. If a small change results in larger groups, go the other way in small increments until your load starts to open up again. Not every rifle will print a single hole or clover leaf. some rifles and loads will tighten up to a 1" group at 100 yards and you should be thrilled with this. SOME rifles will tighten up all the way to a single hole. Some rifles won't tighten at all. If this happens to you, change your components. Heavier bullet, different powder, even changing primers can make a difference. I got lucky. VERY lucky.
BUt where should you start? well...alot of factors and thoughts exist here. One thing I like to do is find my MAX seating depth using a dummy round. I will load an OCW test of 3 rounds each and work from light to heavy with the bullet FULLY engaged in the lands, at .015" greater than what the dummy round tells me. Some force will be required to close the bolt. as you work up, pay NO attention to groups or impacts, but pay VERY close attention to the brass and primers as you extract the spent round. ANY difficulty in removing the spent case (stuck bolt handle) means you are AT MAX. Flattened primers means you are AT MAX. the moment you start to see signs of pressure on your brass, STOP. this charge should be considered YOUR max charge PERIOD. Use this value for the number on your OCW spreadsheet. My rifle was difficult to test this because loaded rounds were too long for the box magazine and had to be loaded into the chamber one at a time. I ended up with 47.00 grains of varget with the bullet engaged into the lands at .015" greater than the dummy round.
Then I started working the load at .02" off the lands with my OCW test. I determined that my bullets were consistent at the 45.5gr mark and were stringing, so i started working the bullets back into the brass. I ended up with (get this) 2.800" OAL which is SAAMI standard for .308WIN anyway (Yay!) and my resultant load after a few trips to the range is 45.5 gr varget, cci primers, winchester brass, FL sized and trimmed with Hornady 150gr bullets at COAL of 2.800". and (drumroll please...) my final target after all this:
actually, i can't find the 45.5gr target, but it looks just like this early test with 45.0gr - a group size of .172"-.200"
I also have an OCW load worked up for RL15 and 165 gr SGK's. My rifle simply did NOT like varget with the SGK's at all, but as soon as I started working with RL15 (45.0gr RL15, 165gr SGK SPBT's, win brass, cci primers, fl sized and trimmed), i was able to consistently achieve: