Coharie CA89-10 with:
Michael Machines barrel
HK German complete bolt & carrier
Aftermarket A3 stock with HK buffer
HK recoil rod
HK German mags
Bolt Gap .010-.011”
Sellier & Bellot 180 gr FMJ
NOTE: S&B has started a case to determine why much of their brass is splitting.
I had a single FTE on round #4 on semi then she purred thru the next 120 rounds semi & FA. I switched to my Blackthorne stock ( that I’ve mostly used over the years) & FTE’s started. Put the A3 on then several FTE’s as well. Replaced the extractor & extractor spring with HK parts & no help. I called it a day. I’m open to suggestions.
The cases in your picture are very clean and I would say you cleaned them after firing so the splits would be more visible?
Otherwise, where are the flute marks? Apologies if this has been asked/answered.
Update: I can’t begin to tell you what a pleasure it has been communicating and doing business with Mike Otte! Mike determined the following: 1) the bolt was hitting the trunnion causing a slight shift which has been beating the bolt 2) a spot in the left side of the trunnion & inside of it was removed 3) my receiver rails were not properly aligned with the trunnion. Mike was able to straighten them. 4) my extractor had some movement so he replaced the extractor spring. He tested & bolt no longer hits trunnion. I then replaced the beat up ejector (see above) and took her to the range today. I put the A3 stock on and proceeded to load 25 rounds of each of the following: (all 180 FMJ & Hi-LP):
9.1 gr Longshot
8.7 gr Longshot
8.0 gr Power Pistol
S&B (same lot with split cases)
10.5 gr Blue Dot
All ran 100%! Thanks Mike!! I received World Class Service with great communication and a more than fair price!
Jet: hard to know. Even though Mike Otte fixed a spot in the trunnion & squared up my rails, he said he felt it was bad brass. All of the Ammo he test fired had no splits & basically looked the same as if fired in his HK MP5-10. Bottom line: I’ve been on cloud 10. My gun has never run like this! I chose to add +4 rollers. My BG has held at .014 now after firing 300+ rounds. Thanks again Mike!