Once your loading bench is set up in a convenient fashion, put the full length resizing die in your press, The shell holder should make firm contact with the bottom of the die when the ram is in the fully raised position; you should be able to feel the handle cam over when its at the end of its travel. Lock the die in place with the lock ring. Lightly lube the case from the shoulder down, if possible use dry neck lube in the case mouth to prevent the expander ball from dragging. Resize each case and wipe the case lube from each resized case.
I assume that you've purchased loading manuals as well as your handloading tools, so break open the manual of your choice to the .300 WSM page. You will note the trim to length and/or the cartridge diagram with the dimensions printed around it. Measure your cases to unsure they are 2.1" long or slightly shorter, and trim those that exceed that length. New brass is occasionally too long. Next you need to deburr and chamfer your case mouths. Don't go crazy here, just knock off the rough brass on the outside of the neck and put a gentle chamfer on the inside of the case mouth the the chamfer-deburring tool.
The next step is to prime the cases. The rule of thumb I prefer is when the powder charge exceeds 50 grs, or when ball powder is used, or when the load is used in extreme cold, use a magnum primer. All of your loads will exceed 50 grs, so the choice of a magnum large rifle primer is appropriate. Seat a primer in each cartridge case. Ensure the primer is fully seated, which can be detected by feeling for a raised surface on the case head, or it the case is stood up on a flat surface and it rocks, the primer needs to be deeper.
To set up the seating die, put an unloaded cartridge in the shell holder and run the ram up to the top of it's travel. Screw in the seating die until you feel it come into contact with the case mouth, then back off the die a quarter turn or so, and lock it in place. If your bullet has a cannelure or crimping groove, seat to it, if not mark the bullet with a Sharpie so you know how deep to seat the bullet, the minimum should be about 1 caliber, so from the base of the bullet put your mark about a third of an inch up from the base of the bullet. Through trial and error get the seating stem to the correct length and lock it in place.
If you use a balance beam scale, its beneficial to have it at eye level. Zero the scale, then what i like to do is confirm the scale is measuring correctly, using a scale check weight set.
Now refer again to the manual. Go to the bullet weight you've chosen to use, and select your powder type. One way to do this is to simply find which powder produced the highest velocity, this isn't the worst way to proceed for a hunting load. If your manual shows powder density, it is better to avoid powders that compress beyond 100% of the case capacity, as these are fussier and slower to load. You will note that each powder has a start load and a maximum load. If you haven't loaded for this rifle before, you want to use the start load, and work up from there. So begin making 5 rounds of the start load, write the load right on the brass with a Sharpie, and enter the load in your record book. Now proceed to make 5 rounds of each load with 1 gr increments until you reach the maximum load. At this point you might want to make up a couple more at half gr increments, but understand, that you might hit the maximum load for your rifle before you ever get to the maximum load, and you'll have to pull all the remaining loads.
If possible set up a chronograph at the range. The safest way to determine you r maximum load is to stop when the instrument velocity matches the book velocity. Maximum book velocity for a 180 in a .300 WSM is about 3100. Watch your brass though. Examine each one carefully for pressure sighs, and be aware that these signs can be sublte and in some light conditions difficult to see. You're looking for extractor marks which show up a shiny marks on the case head, watch that the bevel between the edge of the primer pocket and the primer doesn't disappear, and you might want to measure case head expansion at the web of the case, although this doesn't mean much with new brass, its still good to record it, so you can note any change on the subsequent loadings. If you encounter a stiff bolt lift, stop, do not shoot any higher load, this is your last chance before a serious failure might occur. Once I have determined the maximum load, I reduce that load by 1 full gr and use it as my working load. It won't show much lower velocity, if any, and it will allow for tolerances of bullet weight and case capacity with your future loads. Note in your record book the maximum load and the working load.
Now load up a batch of ammo and check to ensure it falls with the acceptable parameters of accuracy. As long as it does not exceed 2 MOA, it is suitable for big game hunting out to 300 yards although it should by rights be well under 1.5 MOA. If you intend to use the magazine of your rifle, your OAL must be short enough for the rounds to cycle though the magazine without hanging up. In many cases this does not but the ogive of the bullet at the optimum distance from the lands for best accuracy. You might find that crimping the bullet is a benefit in that it uniforms the bullet pull weight, which is otherwise controlled by the distance of the jump to or jam in the lands.
Crimping is best done as a separate step from bullet seating. Back off the seating stem, then back off the seating die a few turns. Run the ram to the top of it's travel with a loaded round on the shell holder. Now turn in the die as far as it will go, back off the press handle a bit, turn the die in another eighth of a turn, and fully raise the ram. what should result is a nicely crimped cartridge. You might find a a Lee Factory Crimp die provides more uniform results. Be advised, in this matter of crimping, my ideas seem to be the exception to how the majority of handloaders work. The best advice I can give you is to shoot both crimped and uncrimped rounds, and use the system that makes the most sense for you.
Hope this helps.
