Ignition system question and thoughts

[BoydAllen]

Generally speaking factory firing pin protrusion has been more or less standardized at about .055", but when actually igniting a primer the pin only goes as far as the prime lets it, which has been reported to be under .030. From this we can conclude the actual in use firing pin fall is reduced by the difference between .055 and the actual amount that the pin sticks out from the bolt face when firing, which is a little over .025, which seems to be significant for actions that have marginal FP fall. Beyond that we have some clearance between the cocking piece and the bottom of the cocking cam notch to work with. by turning a little off of the front of the firing pin flange the working depth of the notch could be increased with no harm as long as there was some clearance, which really only comes into play when dry firing since the cocking piece does not fall to its limit in live fire. To take advantage of this slight reshaping of the front of the pin might be required depending on the original clearances. So what do you all think of these proposed methods to increase effective pin fall. It seems to me that a FB protrusion of .040 should work just fine as long as case fit is to match standards. Do any of you have actual experience with this?

 

[AlNyhus]

Boyd, on one of my HV 30BR Pandas (.055 pin prorussion and 23 lb standard spring) the front face of the collar was faced off .020 and I experimented with stacking .010 thick Nylon washers to see how pin protrussion affected it. At .045, it still shot very well. At .035, the groups started to get loose. Took it back to .055 and it shot dots again. I never went past .065 but there was no difference there than at .055. In all cases, there was clearance between the tail of the cocking piece and the bottom of the cocking piece notch in the bolt. Pin tip was .068 with the standard Kelbly profile.

With the stacking involved, I think you need at least .050 to get that theoretical .030 'magic rabbit' number. The primer pushes back against the pin tip when lighting off the primer mix and powder...
the .030-ish fired primer indent depth is misleading.

Just a sample of one but there it is.

Good shootin' -Al

PS- I use that firing pin as a punch, now.

 

[BoydAllen]

Al, thanks for the information. What I would like to know is the difference between the depth of the dent in the primer comparing, firing a round and just firing a primer in a properly sized case, taken by measureing from the back of the shroud to the back of the cocking piece. With this information and the same measurement taken with the firing pin uncocked and the chamber empty, we will be able to put together a useful plan for increasing effective firing pin fall, with minimal effort. Of course since the Panda is well known for having plenty of firing pin fall, none of this would make much of a difference for your action.

 

[Alex Wheeler]

In my opinion you cant cheat ignition. The deepest I have measured primer indention is .026". This does not include any shoulder setback or headspace. It also does not include how much below flush the primer is set. That was also with a cci br4. A federal would cetainly go deeper. I did my test with Bats which have a .070 pin tip. The .062 pins will do deeper yet. .055 is a good number to use, Id go as shallow as .045 if I knew the guy. You do not want the fp to bottom out ever, even if it bounces back and you cant measure it. Its not an area I want to push the limits. It does not take that much more effort to open a bolt with .010 or .020 more pin fall. The only reason we try to cheat this is because its not easy to recut the cocking cam and fix ignition.

 

[Michael Huebner]

Al, thanks for the information. What I would like to know is the difference between the depth of the dent in the primer comparing, firing a round and just firing a primer in a properly sized case, taken by measureing from the back of the shroud to the back of the cocking piece. With this information and the same measurement taken with the firing pin uncocked and the chamber empty, we will be able to put together a useful plan for increasing effective firing pin fall, with minimal effort. Of course since the Panda is well known for having plenty of firing pin fall, none of this would make much of a difference for your action.

Boyd,
I increased my fall on my BAT DS Actions and I think I have done what you are asking.
0.032” indent on a primer (nil powder etc)
On loaded round 0.022 to 0.023” indent (the load does make a difference) on N133 and 65BT bullet seated in lands.
Action has around 0.248” fall with custom 0.280 diameter pin and 24lb spring combo.
This is using 0 hanger and Flavio trigger. That’s also pin at around 0.054 protrusion. This combo hits the primer with around 25% more energy from memory. Have the calcs somewhere.

Prior it had loaded primer indent of around 0.016” using Dwight’s tungsten weight and spring combo on the old 1/4” pin and around .210 Fall (0.010” hanger)
On old setup I had to load the spring up with 2 x weights and use 0.020” hanger to get 0.021” indent which made the action to hard too use.

Now I have it set up my current way I will never go back to under .245 on the BAT Action.

I will try a reduced pin protrusion pin probably at 0.040” (.260 pin fall) but later in the year after September, busy til then.

Cheers
Michael

 

[BoydAllen]

In my opinion you cant cheat ignition. The deepest I have measured primer indention is .026". This does not include any shoulder setback or headspace. It also does not include how much below flush the primer is set. That was also with a cci br4. A federal would cetainly go deeper. I did my test with Bats which have a .070 pin tip. The .062 pins will do deeper yet. .055 is a good number to use, Id go as shallow as .045 if I knew the guy. You do not want the fp to bottom out ever, even if it bounces back and you cant measure it. Its not an area I want to push the limits. It does not take that much more effort to open a bolt with .010 or .020 more pin fall. The only reason we try to cheat this is because its not easy to recut the cocking cam and fix ignition.

Thanks for responding. The effect of cumulative clearances is exactly why I have switched to looking at this issue by measuring differences in the measurements from the back of a shroud to the back of the cocking piece. By starting with the measurement with an empty chamber, and then looking at what it is with a properly sized case containing only a primer that has just been fired, and knowing the firing pin protrusion I can see how much the difference is shortening the fall during actual firing, what I have taken to calling effective FP fall. I cannot see how reducing excess protrusion a bit would hurt as long as the front of the pin flange does not contact the inside of the bolt. Beyond this, I am looking at the clearance between the nose of the cocking piece and the bottom of the cocking cam notch to see if there is any usable excess that could be used by taking a little off of the front of the FP flange. If all of this would gain say .015 with no harm then what would be the harm. Of course the whole thing would require actual testing to confirm, and since my PPCs action is a Stiller Viper, and it seems to work in that application the way it is , and I do not know where I can get a replacement pin, at present this is just a theoretical exercise, but if I find a FP source, that will change. Currently my empty chamber fall is .220. Looking at the dent in fired primers I can see evidence that the pin has been backed up by pressure on the inside of the cup. I do have one experiment that I can do with what I have. I have a short action Rem. (same as my action's) spring that is the heaviest that Wolff sells, and it would be interesting to change it out at the range on a day where the wind would favor fine comparisons in accuracy. Since I have not been to the range for a while because of health issues, perhaps my next move will be to rig up an old bath towel to muffle the sound of a fired primer and take some measurements. Thank you for all the good information you have taken the time to share.

 

[BoydAllen]

Boyd,
I increased my fall on my BAT DS Actions and I think I have done what you are asking.
0.032” indent on a primer (nil powder etc)
On loaded round 0.022 to 0.023” indent (the load does make a difference) on N133 and 65BT bullet seated in lands.
Action has around 0.248” fall with custom 0.280 diameter pin and 24lb spring combo.
This is using 0 hanger and Flavio trigger. That’s also pin at around 0.054 protrusion. This combo hits the primer with around 25% more energy from memory. Have the calcs somewhere.

Prior it had loaded primer indent of around 0.016” using Dwight’s tungsten weight and spring combo on the old 1/4” pin and around .210 Fall (0.010” hanger)
On old setup I had to load the spring up with 2 x weights and use 0.020” hanger to get 0.021” indent which made the action to hard too use.

Now I have it set up my current way I will never go back to under .245 on the BAT Action.

I will try a reduced pin protrusion pin probably at 0.040” (.260 pin fall) but later in the year after September, busy til then.

Cheers
Michael

Michael,
Thanks for all the information. Please let me know about your results when you decrease your FP protrusion. Other than the increase in shaft diameter, were there any other differences between the stock pin and your custom one? I presume the reason for the increase in diameter was to increase pin mass, or was there something else? Did you step the pin to fit the shroud or bore the shroud? Again, thanks for all the information.
Boyd

 

[Michael Huebner]

Michael,
Thanks for all the information. Please let me know about your results when you decrease your FP protrusion. Other than the increase in shaft diameter, were there any other differences between the stock pin and your custom one? I presume the reason for the increase in diameter was to increase pin mass, or was there something else? Did you step the pin to fit the shroud or bore the shroud? Again, thanks for all the information.
Boyd

Boyd

I was inspired by Alex Wheeler’s post on updating the BAT ignition and also Stiller and Greg Walley’s comments on ignition.
So I went straight to what they all concluded was required.
What I have done is what’s needed to go to 250 plus fall. You need to machine action and bolt helix, make pin dimensions fit new fall.(Well at least on my DS and B actions)

The main reason for 280 pin is BAT changed to everything 280 pin shrouds and the springs he stocks suit that pin, although the spring I use is not a BAT item.
FYI the Dwight Scott weight and 1/4” pin pretty much weighs the same as the new BAT 280 pin.
The pin I made is within 1 gram of the 280 BAT pin, so basically the same.
The shroud was made to function with the new 280 pin
Photos
Dwight kit shown on 1/4” pin
Custom Pin and Spring complete
Modified Bat pin for .250” fall (I trialled this first before I made the custom pin)
Custom pin compared to modified BAT .280 pin

 

[PatMiles]

Following

 

[WSnyder]

I’ve done similar things as to what’s been stated above. I aim for .250” min pin fall. I’ve tried pin tip protrusion down to .035”. On my personal guns I’m using .045-.050. For someone else .055”min. As a side note I recall Savage engineer Bob Greenleaf said he set his Savage’s up with .035”. Being a Savage it may or may not be applicable to this discussion.