Reloading 300 BO Experience

[TomN]

I recently decided to start reloading 300 BO. I have a Dillon XL650 that I have used to load 9mm and 45 ACP with good results. I purchased a set of Lee dies for 300 BO. I loaded 10 once fired commercial brass cases (not crimped primers) using Speer 125 gr TNT, CCI 41 primers and 18 gr of Enforcer with an OAL of 2.010. Off to the range and all functioned as expected, no problems chambering or firing.

I had some once fired Lake City 5.56 brass I wanted to make into 300 BO, I bought a cutoff saw and jig, I cut a couple of cases and checked the length, all was within spec so I and proceeded to cut about 20 cases. Next I punched the primers and full length resized the cases. Knowing the crimp needs to be removed before priming I used a "reamer" to remove the crimp. I loaded the 20 rounds exactly like the first 10. I did a "plunk" test on all 20 rounds and they passed.

At the range testing the loads, on the third round I noticed the primer was not in the fired case. I looked at the first two cases and the primers looked good, they were not flattened so I do not think over pressure was a concern. I continued to shoot the remaining cartridges and at the end of the session, 7 of the 20 fired cases did not have the primers in them. I went home and loaded another 10 rounds using commercial 300 brass (no crimp) and shot them, no problems with primers. This makes me believe I took out too much material trying to remove the crimp.

I borrowed a Dillon 600 Swager and swaged another 20 of the Lake City brass and reloaded them like I had all the rest. At the range I shot 6 with no problem, all primers were in the fired cases. The 7th round did not fire, looking at the primer there was not even a mark, I tried it again, it did not fire and no mark on the primer. I continued to shoot the remaining 13 rounds having one additional round not firing. No visual mark on the primer.

My explanation for the last two rounds that failed to fire are a result of the "shoulder" not being resized/formed correctly. This allows the cartridge to be far enough from the bolt face that the primer does not strike it. I don't understand why this happened because I have used the same die set for all the resizing. I would be interested in your thoughts and suggestions. Should I get a specific "forming" die to run them through prior to resizing? Have any of you experienced anything similar? Cheers, Tommy

[imashooter2]

I’ve read complaints about the Lee dies not forming cases correctly. I don’t understand how dies that resize correctly wouldn’t form, but the reports are out there. The only dies available when I started were Hornady, and they have formed all my LC cases perfectly.

[TomN]

This is exactly the type of response I was hoping to get, I hope others will share their experiences. This gives me something to consider. Thank you for taking the time to respond! CHeers, Tommy

[GeronPG]

I began reloading the 300 BLK about 8 (?) years ago using trimmed .223 brass formed in Lee dies. Mine also came with the factory crimp dies. My loads have been dependable and accurate, with no issues. All are fired in an AR-style semi-auto.

[GeronPG]

I suppose it's possible that the sizing die could be manufactured incorrectly. Another possibility may be if you used a different brand shell holder that let the case go too far into the die, moving the shoulder back too far (?) Another possibility might be if in swaging the primer pockets, they became a little large or loose, so that they're not firmly supported for the firing pin strike (?)