Changing firing pin prutrusion as a way to gain a little effective pin fall?

Let's try again. If you build a firing pin that was identical to the one that came in your bolt, except that the tip was so long that is was flush with the bolt face when the pin was cocked, you would have the same fall on an empty chamber, but in fact, for the purpose of setting off a loaded round, there would be very little net fall, and probably not enough energy to dent the primer significantly or set it off. Then let us trim off say .050 off of that tip. The net fall would increase by that amount, whereas the fall on an empty chamber would remain the same, because its stopping point continues to be contact between front of the shoulder of the the firing pin, and the inside of the bolt. We can progress with cutting off the tip of the pin, gaining net fall, until we reach the point where the front of the pin shoulder contacts the inside of the bolt, at which point we will have reached our limit, or more than likely gone past it, since I am sure that having the pin bottom in this way would create an undesirable vibration that one may guess would be detrimental to accuracy. Long and short of it, the trigger is not involved because the distance from the cocking piece to the front of the firing pin shoulder is not changed. Neither is the pin fall on an empty chamber. The protrusion is decreased in direct proportion to the shortening of the pin tip, but as long as it sticks out farther than a primer will allow it to, when firing, there should be not detrimental collision inside the bolt, and there should be a small amount of increase in energy delivered to the primer.
 
One test I never did, but which maybe someone would like to try, is to ream out some flashholes as large as possible leaving only a rim for the anvil to bear on. My intent was then to test for "blowback" with live primers VS dead primers to see if I could test stuff without killing primers by (hopefully) eliminating the primer backblast effect or pushback on the primer cup.

al
 
A while back, Jerry Stiller posted that he is of the opinion that increasing spring weight and striker fall may not eliminate the need for sufficient pin fall. This started my thought process as to how some net fall might be gained. [emphasis added]
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I'm lost. If it isn't too much trouble, what would the difference between striker fall and pin fall be (assuming apples to apples -- your loaded chamber explanation)?
 
ok this may be breaking some kind of law. this is the picture i'm looking at in Boyer's book..If fireing pin travel(fall) is measured in this way decreasing the pin protrusion in any way would be decreasing pin fall.. boyd i do understand what your are saying but i do believe the pin does dent the primer the full or close to full protrusion, just take a fired case look at the small dent in the primer then reinsert the fired case and pull the trigger on it and remove it and you will see a huge dent in the primer, so they say you need .050 to .060 protruision.I'm sorry boyd but i think it looks like the pin does protrude that far under fireing and decreaseing it any would decrease pin fall. to no gain at all only loss of protrusion.
 

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Charles,
They are the same thing. I am just talking about the fact that if we have more protrusion than we need, that shortening the pin tip to reduce it will increase the pins fall to the point where the primer stops it, because there is a difference in that and where it stops on an empty chamber.
Mark-x,
IMO "firing" a used primer a second time is not a reliable way to see what the depth that would happen on a new primer, because you are adding the deformation of the second strike, to the first. I have done what you described.

The reason that I think that we have some protrusion to spare is that Bob Greenleaf and others have reported setting Savage protrusions to .035 with no problems in function. Savage firing pins are adjustable in this respect.
 
Boyd Allen said:
Charles,
They are the same thing. I am just talking about the fact that if we have more protrusion than we need, that shortening the pin tip to reduce it will increase the pins fall to the point where the primer stops it, because there is a difference in that and where it stops on an empty chamber.
Mark-x,
IMO "firing" a used primer a second time is not a reliable way to see what the depth that would happen on a new primer, because you are adding the deformation of the second strike, to the first. I have done what you described.

The reason that I think that we have some protrusion to spare is that Bob Greenleaf and others have reported setting Savage protrusions to .035 with no problems in function. Savage firing pins are adjustable in this respect.
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Boyd,

In an ideal world, your premise would be valid, only use enough protrusion to crush the primer pill and ignite the compound. Theoretically, anything more is a waste of energy. Anything more , theoretically, introduces unneeded vibrations and more variables. I must emphasize "theoretically". Practically, I would NOT be comfortable with less than 10% more than what is needed to make things go "bang". This is coming from a guy who has shot a bunch of good groups and good aggs with a Hall. I think Alan has some great ideas about action design, the basis of which is do the least to get the job done, but firing pin travel and firing pin kinetic energy is not one he thinks is significant. He tries to keep EVERYTHING on the bottom end of needed. And thus you will find yourself chasing many issues if you do not know the the cause when you own a Hall. There are a few of the other current crop of action builders who have seemingly similar problems, your gunsmith should know who they are. I would listen to your 'Smith.

I would be more worried about total firing pin travel and spring tension than I would be about protrusion. .100 protrusion with only .200 fall is a lot less usable kinetic energy (inertia) than a pin with .200 fall and .025 protrusion, especially when you consider that the primer S/B less than .005 in front of the face of the bolt. Again, ideal world.

David
 
David,
Thanks for the information. I think that I know what makers actions are getting a little extra work by some smiths. I was just trying to have this discussion without making a direct reference.

Your information about Halls, is right in line with my point. Assuming that we are talking about any action that is for whatever reason a marginal on kinetic energy delivered to the primer, we can add to that number in a number of ways. I was just proposing an alternate that may not have been considered...by some. If one can safely gain .015-.020 of effective pin fall (the distance from full cock to stopped by the primer before any blow back) with no complications, why not do so? It has the advantage of being simple, and assuming that replacement pins are available, easily reversible.

On the subject of Halls, I seem to remember some favorable comments, and on the one occasion that I shot one, I enjoyed the experience. Although I have not had any experience with one issue that some seem to have had with these actions, it would seem that one might be able to solve it by meloniting the bolt. What do you think of this idea?

A long time back, I had a friend that was somewhat incautious when making a primer change in a couple of loads that were already apparently too close to the edge. He blew primers out of cases in two custom actioned varmint rifles, one with the usual bolt lug and raceway layout, and the other a Hall. I'm sure that you know which one contained the brass bits and gas better.
Boyd
 
Any way you slice it you still have to get about 0.020" penetration of the firing pin tip into the primer cup to get consistent ignition!!
 
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