Boyd Allen
Active member
Although this is not about a BAT, I will mention it because the subject seems to have changed. Another variable is firing pin tip size. I have a viper. They have .062 firing pins. As I understand it, when the action was in prototype stage, tests were done using an Ohler 43, and a strain gauge on the chamber, to look at the pressure rise curves produced when various weight striker springs were used. I believe that the thought was that since the smaller firing pin tip would require less spring weight, to see just how light one could go, given the bolt lift advantage. I believe that tests were done down to about half the spring weight of a Remington (which also has a much longer fall. Evidently there was no sign of a problem, as far as the shape and uniformity of the pressure cure went. Later, when I got my action, I measured its spring at about 19#.
Jumping forward a few years, Greg Tannel started offering a firing pin/spring combination that features a fluted aluminum shaft for a total pin weight that is a little over 60% of the stock unit. Testing by Greg had shown that a heavier spring was needed for this pin, so it came with a 25# spring. My thought was that the lighter weight would produce less vibration. Later an article in PS showed that with this combination, the energy was equivalent to that produced with the factory parts, that the momentum was significantly reduced. When I made the change, I noticed that cross hair movement when dry firing was reduced, and It seemed that there might have been a slight improvement in group size. I should also mention that earlier testing showed that this was also affected by which rear bag was used. (Recently, I found that m newest rear bag showed no cross hair jump with the same test (no case).) Since it has been a while since I made the change (during which time I have had no problems) my next move will probably be to do another test of the stock parts with the new bag. I will also try the heavier spring with the stock pin. One thing that has changed since the first test is that I have been using a couple of wraps of thick teflon tape on the shroud threads, to damp vibration. I do this despite the fact that my shroud fit seems to be good, as an added measure toward vibration reduction. (There was an earlier thread on this topic, in which in at least in one instance this showed improvement at the target.) In summary, I agree with those that think that there is more to ignition than simply setting primers off. Beyond that there seems to be a lot of guessing based on the dreaded anecdotal information.
I will continue to follow threads related to this topic with great interest.
Jumping forward a few years, Greg Tannel started offering a firing pin/spring combination that features a fluted aluminum shaft for a total pin weight that is a little over 60% of the stock unit. Testing by Greg had shown that a heavier spring was needed for this pin, so it came with a 25# spring. My thought was that the lighter weight would produce less vibration. Later an article in PS showed that with this combination, the energy was equivalent to that produced with the factory parts, that the momentum was significantly reduced. When I made the change, I noticed that cross hair movement when dry firing was reduced, and It seemed that there might have been a slight improvement in group size. I should also mention that earlier testing showed that this was also affected by which rear bag was used. (Recently, I found that m newest rear bag showed no cross hair jump with the same test (no case).) Since it has been a while since I made the change (during which time I have had no problems) my next move will probably be to do another test of the stock parts with the new bag. I will also try the heavier spring with the stock pin. One thing that has changed since the first test is that I have been using a couple of wraps of thick teflon tape on the shroud threads, to damp vibration. I do this despite the fact that my shroud fit seems to be good, as an added measure toward vibration reduction. (There was an earlier thread on this topic, in which in at least in one instance this showed improvement at the target.) In summary, I agree with those that think that there is more to ignition than simply setting primers off. Beyond that there seems to be a lot of guessing based on the dreaded anecdotal information.
I will continue to follow threads related to this topic with great interest.