Ive been reloading 300 PRC for a Barrett MK22. I have learned a lot through the process. Im using Lapua Brass, Both H1000 and N565 powder, Hornady ATIP 130 gr and Berger 220 gr. Long Range Hybrids projectiles, Federal GM215M primers. I consistenly get single digit SD, ES around 15-20. Groups depend on how I feel that day. Most below 1/2 min with an occasional 1/4 min.
The 300 PRC seems to be a pretty picky round compared to something like a 6.5 CM or 6BR. I think it may be because its a relatively new round and the reamers have not yet been optimized by the competetion market. That being said, I still love the round!
I am finding that primer seating depth also makes a pretty big difference in this round. I went with the PCPS adjustable priming system from UglyReloadingUSA.com. You will also want the Accuracy One primer seating gauge and the Accuracy One bullet seating depth comparator to measure your actual seating depth. Ask John at Accuracy One which body you need.
I am currently evaluating primer seating depth. As a starting point, I took the deepest measured primer pocket - The standard primer height (not including the anvil) and added .002. Using Lapua brass and Federal GM primers, this is 0.00!
My process for brass prep involves annealing every time. I use an AMP (Annealing Made Perfect) machine. It is the only machine that I found to be consistent. I actually found my other machines to be detrimental in my case prep.
My reloading process from start to finish (Warning, it is slow and a little excessive):
1) Deprime the brass with a Frankfor Arsenal deprimer.
2) Clean the brass necks with steel wool and a drill adapter.
3) Brush the case necks with a nylon brush in a drill
4) Clean the primer pockets with a hand cleaning tool
5) Clean case necks and primer pockets after brushing with alcohol. (I do this because it makes me feel better)
6) Anneal the brass with the AMP
7) Full length size the brass using Imperial sizing die wax and the expander removed from the die. (2 thou bushing)
8) Clean the brass with alcohol again to remove the case lube
9) insert the case neck in a graphite media (Imperial) and immediately run them through an LE Wilson .307 expanding mandrel.
10) Clean the case necks again with alcohol and some cutips to remove most of the graphite
11) Brush the necks again with the drill to even out whatever powder is left
12) Run all the cases through the Henderson trimmer. (Great choics BTW). I also like to re-brush if I have time to remove burrs!
13) Press in primers using a tool that allows precise measurement.
14) Measure powder using an analytical balance. Im saving for an automatic system.
15) Press in the projectiles using an AMP Press.
As far as books, skip it. There are some great reloading videos on youtube. My advice is to keep great notes. I keep track of the actual measured charges of each round, the terminal seating force, primer seating depth, etc. Im getting to where I can predict a flier and remove it from the group. I use those as fowlers.
Things I have learned:
1) optimal case headspace doesnt become obvious after the first firing. Slowly increase your headspace until they even out and eventually normalize. I start with the largest headspace measurement after a firing and check if it will chamber. If it will, I'm setting that as my new full length sizing die headspace the next time I reload. When they begin to standardize, drop .002 and lock in the sizing die. If they will no longer chanber well, you know.....
2) find out the real bullet lenth of your chamber before it sticks. Use this as a starting point for your ladder test of length. If you have the Accuracy One gauge, it helps evaluate consistency. If you are a Barrett guy, the measurement from shoulder to ogive is .210 in a Barrett MRAD using 230 gr ATIP and a measure headspace of 2.1945. This will still load in a magazine and give pretty good results as a starting point. I saw a video by Eric Cortina showing how to test this.
3) Primer seating depth matters! Really! Research this and conduct some tests. I cut my SD and ES in half!
4) Find a reloading mentor or two. Steal everything they have to offer!
If you are in the NC, SC areas, you are more than welcome to come and review tools, spreadsheets, etc.
Good luck! You are going to be amazed with the tools that are now available!!!
P.S Sorry for Rambling. I am drinking and texting!
