I spoke with Aaron at Zermatt over the phone, looking for some info concerning accuracy & ejection issues I was having with a new RimX I'd just barreled myself. I used a Bartlein blank, and had set headspace so the bolt would just close on the included headspace gauge, and initial accuracy was awful. Also had quite a few failures to eject. When I explained that I'd used their headspace gauge as a go gauge, he stopped me right there and told me it's intended as a no-go gauge, and mentioned that fact was on the included info card in the box. Thinking maybe I'd missed that tidbit of important info, I went back and looked the card over carefully - the only reference to the gauge is where it says the extractor & tensioner have to be removed from the bolthead before trying to close the bolt on the gauge - no mention of why the rim in this gauge is so thick - IIRC, .052". So, feeling rather ignorant and stupid for not calling first after measuring the rim on the gauge and finding it was so thick, I pulled the bbl & set it back .010". The accuracy improved by a bunch, but I was still having nearly 20% failure to eject. I also wasn't seeing much if any engraving of the front driving band of the bullet by the lands, so pulled the bbl again, and this time, set it back .070", which allowed my EPS reamer to cut pretty much an entirely new leade area. New SK rounds chambered & removed showed plenty of engraving on the front driving band of the bullet now. The EPS reamer also has a .010"-.015" radius ground at the junction of the body/rim, so it was cutting a nice radius on the mouth of the chamber. All I needed to do was polish it a bit with the rounded-end of a very fine grit Cratex rod while spinning the bbl in the lathe.
Moving on to the failures to eject - Aaron & Ray both said I needed to check the extractor under magnification to make certain it wasn't damaged by chambering rounds before setting the mag height up. But when I told them that I'd adjusted the mag latches on both my mags as per the recommendation on the card before trying to chamber a round, they both opined that I wouldn't find any damage, and were correct. Somewhere in this thread, I know I read that someone had stoned a bit of radius on the bottom edge of the tensioner's hook, so I got out a set of white ceramic stones and went to work on the tensioner. That little hook area on the RimX tensioner isn't very thick, so I didn't get carried away - just stoned enough of a radius on the bottom edge of the hook so that it was just barely touching the case body with a round seated up into the extractor. Also got out a triangle stone and cut a very slight radius with the corner of the stone in the back corner of the hook to allow the case rim to slide up into the hook more smoothly. Cleaned all traces of the stone work up, blew the bolthead clean with compressed air, reassembled the bolt, torqued the bbl back into the action, and went out to test fire at 50yds. It feeds even more smoothly than at first, the accuracy is excellent, and I had no failures to eject out of the 100+rds I fired after completing the work. So yesterday morning, I pulled the bbl - again - degreased, blasted, and CeraKoted with Armor Black, and put it all back together again. Going to take it out to my range to re-zero the scope at 50yds, then back off to 200 and do some shooting on a rack of 1/4" thick AR500 plates to see how it shoots at distance. Ray has sent out a couple of new tensioners (one that's been tuned) and a new extractor, which is a comfort - if I went a bit too far on the tensioner, it should show up within a few hundred rounds, and I'll replace it with one of the ones he's sent. If you've spent any time taking a close look at the tensioner hook, you'll notice that I removed a fair bit of the sharp bottom corner of mine - that's actually a little more than I intended to stone off it. If it continues to work with 100% reliability as it did a couple of evenings ago, no sweat. If not, I've got parts to try again. Thanks for the help Zermatt!