My experience:
We finished up a BH Origin last evening. It too required an abnormal amount of effort to close into battery. First thing I did was remove the fire control assembly to explore if the barrel had been installed with too tight of breech clearance. That was not the case. The bolt flopped into battery under its own weight with the FC removed.
Next, looked over the machine work. No inclusions visible that would indicate a machine finishing flaw. Now compress the striker spring. It moved freely with predictable resistance derived from compression of the spring. Reinstall the FC and pay attention to the effort required to rotate it into the "installed" position. (the 180* turn you have to make once you get the lug engaged down in the bore) Again, it moved easily compared to the effort required to close the bolt when inside the receiver.
Hmmmm.....
So, tore it back down. I applied some copper "chap stick" copper antiseize to the single lug in the shroud that keys into the bolt. Reassemble. It gets a little better. Work the dog piss out of it and it continues to improve. Pull it apart one more time and put a couple drops (literally) of Remington oil on the striker assembly. Put it all back together and it got a bit better.
Contact client, advise, then go home with the intention of working it more today. One of the staff beat me to it. He dry cycled the action prolly close to 100 times. Then I walk over and start fingering it and the problem goes away entirely.
Neither of us laid a hand on the cocking piece or modified a single part. We didn't even tear it down beyond a normal field strip.
Years ago while working at Nesika:
All Nesika actions were designed as a "cock on open only". Meaning that you do not compress the striker spring any further by closing the bolt (like it does on an M700). IF you were not paying attention during a final assembly and you allowed the bolt the "climb the ramps" you could be certain that the action would destroy itself within 200 rounds of use. This was a design flaw in the product due to material selection. Just wasn't hard/tough enough and this condition results in the lugs of the bolt/receiver destroying one another.
Very frustrating...
Bighorns don't have this problem, but it goes to the point. If you watch the cocking indicator on the shroud as you close the bolt and you witness it moving forward ever so slightly, then you have a CoO only type event and its fine. There's literally nothing to fix here because its doing exactly what its designed to do. If it falls an abnormal amount, there's a problem, but so long as you see it nudge forward a teeny bit, you don't have light strikes on primers, and you don't feel a distinct "tick" when closing the bolt, your fine. Go shoot the piss out of it.
The inverse:
If you see the indicator expose more of itself as you do this, then there's an issue. First, double check. It will expose more indicator as you close the bolt and you'll feel a "tick" as you close. That tick is the lugs on the bolt climbing off the receiver's clearance ramps as they transition up onto the lug abutments. It's pulling (screwing, like a nut/bolt) the bolt forward but the pin cannot move with it because the trigger prevents it. This is a "partial cock on close" scenario. -Same as an M700.
Changing the cocking piece location, distance, angle, whatever, only has the effect of altering this timing. In our case it would have made zero difference as the action was displaying a completely different behavior. It had abnormal friction while rotating. There was no "tick" or CoC indication.
A scenario I offer as an alternate consideration:
I would just put out there that if you go through the trouble of running the action, discovering something wierd, tearing it apart, reading stuff like this online, ordering parts, mailing stuff or doing it at home, and then it suddenly stops. It might not actually be from you replacing/chewing on parts.
It could very well be that whatever was being lethargic in our receiver was doing the same thing in yours and because you tore it down/assembled a half dozen times, you got it to work itself out. The parts you modified could very well end up as a placebo of sorts.
My only point is anymore with big companies like BH, ARC, etc, I'm reluctant to go chewing on the parts as they have a pretty darn good handle on what they are doing.
Hope this helps.
C.
