I have hesitated to weigh in on this thread because I am not familiar with BAT actions. However, I am an accomplished engineer and a precision smith and I think I can add a few thoughts and observations for you to ponder. I have read every part of this thread that you added.
If you look closely at the way a bolt functions while you operate it, you will see that it serves many purposes but only three involve any forces of the type you describe and only two of those are significant to your experience. These are:
1. The extraction cam on the action that engages the base of the bolt handle when the bolt is opened. This minor cam pulls the bolt slightly rearward and serves to pull the fired case loose from the chamber after firing. A tight brass (too much pressure) or a rough cam surface on either the action or on the bolt would increase bolt lift force. But you experience this problem even on an empty chamber when there is no tight cartridge to react against so I doubt that is your issue.
2. Opening the bolt also pulls back the firing pin in preparation for the next shot. This is accomplished with a cam in the rear of the bolt under the shroud. The shroud prevents the cocking piece at the rear end of the firing pin from turning thus forcing the cocking piece rearward against the cam at the rear of the bolt. Once fully opened, the cocking piece engages a flat section beside the cam ramp which then holds the firing pin rearward as the bolt is pulled rearward to fully open it. When the bolt is closed, the trigger sear engages the cocking piece and holds it back until the trigger is pulled. If you remove the trigger or pull it while closing the bolt, the cocking piece (and attached firing pin) will not be held reward and will slide down the cam ramp at the rear of the bolt. That's why your bolt closes the rest of the way down under spring force when you closed it without the trigger engaged.
In my opinion, it is the forces that are in play at the cam at the rear of the bolt that you are feeling. It is certainly NOT any part of the trigger, or scope base screws, or action screws. Your description rules all of these out.
So, if I can be so bold as to conclude that this is where your problem is, I can suggest a few things to look for:
1.Quite obviously, the firing pin spring force is a major determinant of the bolt lifting force. The stronger the spring, the harder the bolt lift force.
2. The steeper the cam ramp at the rear of the bolt, the harder the bolt lift force.
3. The more friction in the cam the harder the lift.
4. Other frictions can also add to the required lift force such as internal friction on the firing pin spring inside the bolt, internal friction on the threads in the shroud (which always turn as the bolt opens or closes), or on the sliding surfaces of the cocking piece inside the shroud.
My advice to you is to take the bolt apart and examine it closely to fully understand what I have described, then make sure that all these parts slide smoothly, that there are no burrs or rough surfaces or edges, and that they are all properly lubricated with a very light gun grease, and then assemble the parts again and watch these various parts move while feeling the forces involved.
If after doing all this, you still have a problem, I would give careful consideration to your own sensitivity to the issue. It may well be that while you think the force is excessive, others might think it is just fine. We are all different and thank God for that! If this is where you end up, it might also help to remember what it happening as you lift that bolt. It's important heavy work. You are extracting a fired case, you are camming the firing pin up into the cocked position, and you are engaging the pin into a detent that holds it in place while you pull the bolt rearward. These are all important functions and a little effort to make them happen is warranted and a good thing.
I must assume that Wheeler is correct and the BAT has a stiffer firing pin spring. He certainly knows his stuff. But he didn't mention the cam angle and a steeper angle would also increase the force. But that isn't a bad thing. Once you understand that you are just cocking a very fast firing pin, you might come to LOVE IT!
If you look closely at the way a bolt functions while you operate it, you will see that it serves many purposes but only three involve any forces of the type you describe and only two of those are significant to your experience. These are:
1. The extraction cam on the action that engages the base of the bolt handle when the bolt is opened. This minor cam pulls the bolt slightly rearward and serves to pull the fired case loose from the chamber after firing. A tight brass (too much pressure) or a rough cam surface on either the action or on the bolt would increase bolt lift force. But you experience this problem even on an empty chamber when there is no tight cartridge to react against so I doubt that is your issue.
2. Opening the bolt also pulls back the firing pin in preparation for the next shot. This is accomplished with a cam in the rear of the bolt under the shroud. The shroud prevents the cocking piece at the rear end of the firing pin from turning thus forcing the cocking piece rearward against the cam at the rear of the bolt. Once fully opened, the cocking piece engages a flat section beside the cam ramp which then holds the firing pin rearward as the bolt is pulled rearward to fully open it. When the bolt is closed, the trigger sear engages the cocking piece and holds it back until the trigger is pulled. If you remove the trigger or pull it while closing the bolt, the cocking piece (and attached firing pin) will not be held reward and will slide down the cam ramp at the rear of the bolt. That's why your bolt closes the rest of the way down under spring force when you closed it without the trigger engaged.
In my opinion, it is the forces that are in play at the cam at the rear of the bolt that you are feeling. It is certainly NOT any part of the trigger, or scope base screws, or action screws. Your description rules all of these out.
So, if I can be so bold as to conclude that this is where your problem is, I can suggest a few things to look for:
1.Quite obviously, the firing pin spring force is a major determinant of the bolt lifting force. The stronger the spring, the harder the bolt lift force.
2. The steeper the cam ramp at the rear of the bolt, the harder the bolt lift force.
3. The more friction in the cam the harder the lift.
4. Other frictions can also add to the required lift force such as internal friction on the firing pin spring inside the bolt, internal friction on the threads in the shroud (which always turn as the bolt opens or closes), or on the sliding surfaces of the cocking piece inside the shroud.
My advice to you is to take the bolt apart and examine it closely to fully understand what I have described, then make sure that all these parts slide smoothly, that there are no burrs or rough surfaces or edges, and that they are all properly lubricated with a very light gun grease, and then assemble the parts again and watch these various parts move while feeling the forces involved.
If after doing all this, you still have a problem, I would give careful consideration to your own sensitivity to the issue. It may well be that while you think the force is excessive, others might think it is just fine. We are all different and thank God for that! If this is where you end up, it might also help to remember what it happening as you lift that bolt. It's important heavy work. You are extracting a fired case, you are camming the firing pin up into the cocked position, and you are engaging the pin into a detent that holds it in place while you pull the bolt rearward. These are all important functions and a little effort to make them happen is warranted and a good thing.
I must assume that Wheeler is correct and the BAT has a stiffer firing pin spring. He certainly knows his stuff. But he didn't mention the cam angle and a steeper angle would also increase the force. But that isn't a bad thing. Once you understand that you are just cocking a very fast firing pin, you might come to LOVE IT!
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