Ok, I have a Toyo Kogyo Series 31 that gets shot on a regular bases in CMP Vintage Matches throughout the year. Last year, I had an interesting phenomenon where I had burned discoloration of the upper portion of some of my cases. I posted this in a Jap Rifle forum last year when it happened. My load at the time was a Hornady 174 gr .3105 dia. FMJBT bullet over 40.0 grains of 4064 and a CCI-200 primer.

Going with some of the advice I received, I changed to a slightly hotter load and more accurate bullet thinking that my case necks may not have been expanding enough to seal. The new load is a Hornady 174 gr .312 dia. HPBT Match bullet over 42.0 grains of IMR 4064 and a CCI-200 primer. This proved to be considerably more accurate! However, things have gone from strange to downright weird. My son shot it on Saturday with the new load for the first time and here's what we have now:

I'm no longer getting that burned appearance on the upper portion of the case and neck. Now, I'm getting a considerable amount of carbon on the rim, head, and bolt head. I have no flattened primers, no pierced primers, no bulging cases, no split cases, no cracked case necks... in short, I have no indication what-so-ever of where this carbon is coming from. My only guess is it's leaking past the shoulder... but I have nothing on the upper portion of the cases. When my son shot it on Saturday, he gave me no indication that there were hot gases blowing out of the receiver either. After cleaning and inspecting the rifle, the bolt and chamber both look fine! Everything appears to be normal. Could it be that I'm moving the shoulder too far back when resizing, and the cases are not fire-forming to the chamber? I'm sizing the same way I have for several years, and this only started last year with the original problem. Dies are LEE Pacesetter 7.7x58 Jap. Brass is both PPU and Norma, and the results are the same for both.

I welcome all discussions