Firing pin fall --a discussion

[Edd]

Firing pin fall is measured on an empty chamber. The front of the firing pin flange is what stops the pin fall when dry firing on an empty chamber. With a Remington style striker assembly, I believe that one would have to remove material from the front of the flange in order for the pin to fall farther. This would also require modifying the pin tip for a couple of reasons. First of all the taper behind the tip diameter might contact the bolt, keeping the pin from falling to the point where the front of the flange contacted the inside of the bolt. Secondly the increased fall would increase pin protrusion in direct proportion to the increase in FP fall. The usual standard for pin protrusion is about .055 but when the pin falls on a live primer in a properly sized case it is stopped by the primer, well short of that. You can make your own measurement on a Remington by comparing how far down in the shroud the back of the cocking piece is after dry firing, and comparing it to how far down it is after firing a live primer. With that difference and the actual measured FP protrusion, you can see how much of the excess protrusion might be, keeping in mind that you do not want the front of the flange to bottom when actually firing a round. Years ago Bob Greenleaf (retired engineer from Savage) toldme that he set his personal rifles for a FP protrusion of .035. Bob was with the company for 25 years. For those who are not familiar the model 110s had adjustable FP prutrusion. To get a better understanding of the whole protrusion thing, Imagine a pin that had a tip that was so long that it was flush with the bolt face with the action cocked, which would make the protrusion equal to the fall. In that case, the pin would only be able to fall the distance to the primer from the bolt face plus the depth to which it deformed the cup. You need to use an empty case for these tests because I believe that in the case of a hot load the primer dent may be pushed back a bit. from where it would be if the primer alone was fired. Excess protrusion actually reduces the effective pin fall and reduces the energy delivered to the primer.

I have previously read something similar to this, I think it might have also been one of your comments. After reading it I decided to use two measurements for firing pin travel. I decided to use the distance from cocked to primer contact as one measurement and firing pin protrusion as the other. I want .200" of travel before primer contact and .055" of protrusion. I prefer the feel of a little bit of cock on close. I've only done a couple of actions but neither of them has over .020" cock on close. .020" doesn't feel offensive to me.

 

[WSnyder]

Ah, so no dremel work.

Yeah, no

Although if you have a combination that just needs the bottom notch deepened a touch mby a dremel would work. I'll still use the mill but that's because I can.

 

[Ledd Slinger]

One thing you most definitely do NOT want in a Rem 700 type ignition system is the cocking piece bottoming out and being stopped by the bottom of the cocking ramp. The cocking piece is only designed to load the spring, not to be used as a device to stop it. The firing pin should be stopped on the shoulder inside the bolt body.

 

[Alex Wheeler]

I had about .210”pin fall on a BR action….. no cock-on-close. By adding a .030” trigger hanger to the system I gained some cock-on-close (not the full 30, but some) and I gained a lot more reliable ignition system.

I think a reliable ignition has got to be the first priority?
Cock-on-close sucks, no doubt about it. Especially when you have actions that a good smith has worked their magic on to compare to. However, a small amount of cock-on-close isn’t hurting anything on the above action and the aggs are smaller because of better ignition.

What percentage of smiths around the nation know how to properly address acquiring at least the minimum pin fall and little to no cock-on-close?

I am not trying to beat up on anyone here, just shining a light in a dark place and furthering my understanding of the ignition system.

CW

If the cocking cam helix is deep enough and the closing cams are designed right timing an action is really basic stuff. When they aren't it's a lot of work and a dremel is not the right tool it has to be done on a mill or it's going to open like sh!t. I have had to fix a lot of dremel jobs. In that case your far better off with cock on close if your not going to do it right.

 

[dave@aDave]

This is a very good discussion. Much to be learned here

 

[BoydAllen]

I had about .210”pin fall on a BR action….. no cock-on-close. By adding a .030” trigger hanger to the system I gained some cock-on-close (not the full 30, but some) and I gained a lot more reliable ignition system.

I think a reliable ignition has got to be the first priority?
Cock-on-close sucks, no doubt about it. Especially when you have actions that a good smith has worked their magic on to compare to. However, a small amount of cock-on-close isn’t hurting anything on the above action and the aggs are smaller because of better ignition.

What percentage of smiths around the nation know how to properly address acquiring at least the minimum pin fall and little to no cock-on-close?

I am not trying to beat up on anyone here, just shining a light in a dark place and furthering my understanding of the ignition system.

CW

What is the firing pin tip diameter of your action?

 

[Mulligan]

What is the firing pin tip diameter of your action?

.066”
CW

 

[michaeljp65]

I have about .228" pin fall on my Panda, i emailed Kelbly's and they recommended a .030 hanger which i purchased and installed, i now have .228" pin fall. No change.

 

[Tim Singleton]

I have about .228" pin fall on my Panda, i emailed Kelbly's and they recommended a .030 hanger which i purchased and installed, i now have .228" pin fall. No change.

Try Turnin it around

 

[dkhunt14]

I had about .210”pin fall on a BR action….. no cock-on-close. By adding a .030” trigger hanger to the system I gained some cock-on-close (not the full 30, but some) and I gained a lot more reliable ignition system.

I think a reliable ignition has got to be the first priority?
Cock-on-close sucks, no doubt about it. Especially when you have actions that a good smith has worked their magic on to compare to. However, a small amount of cock-on-close isn’t hurting anything on the above action and the aggs are smaller because of better ignition.

What percentage of smiths around the nation know how to properly address acquiring at least the minimum pin fall and little to no cock-on-close?

I am not trying to beat up on anyone here, just shining a light in a dark place and furthering my understanding of the ignition system.

CW

Ignition on a rifle for 1000 yards can make or break a gun. Seen some where a weak firing pin spring absolutely destroyed accuracy. Matt

 

[Ledd Slinger]

Ignition on a rifle for 1000 yards can make or break a gun. Seen some where a weak firing pin spring absolutely destroyed accuracy. Matt

Yeah with how many rounds a BR shooter puts thru a rifle, they should probably be changing the spring out at least once a year to maintain peak striking force.

 

[mikecr]

What we need is a standard in 'dynamic strike force' (DSF), for best precision as measured on target.
It would be possible to do,, Jackie mentioned that his 30br was best with .250" PF with 24Lbs of static spring force. That means nothing of DSF, but with that setting, DSF could certainly be measured at a standard distance from bolt face (maybe ~10thou).
Combine adjusted to DSF with a standard in pin diameter, primer, primer seating, and headspace to replicate optimum with any action.

Of course the difficulty would be in developing such a standard, given different primers, and putting it out there in a way that reloaders can adopt. Kit form.
It makes sense IMO for an action maker, who shoots 600-1kyds, to do this. But it could be anyone with the resources, and inclined to leave a positive legacy.

A go-gauge fitted with an instrumented dummy primer. The measure captured by DAS sampling and fed to laptop graphing. Adjustments(one form or another) to PF and spring would be made to match desired DSF.

 

[michaeljp65]

Try Turnin it around

Will only fit one way. Hanger has a notch on top that has to be facing the bolt entry. .236 is the pin fall and the Kelbly hanger is .0200" was hoping for .256"

 

[swd]

Will only fit one way. Hanger has a notch on top that has to be facing the bolt entry. .236 is the pin fall and the Kelbly hanger is .0200" was hoping for .256"

Call Kelly back and talk to them again.

 

[Alex Wheeler]

Kelbly hangers only go one way, theres a notch for the cocking piece that goes to the rear. You probably just need a .050"

 

[tom]

Sometimes a guy just has to do what a guy has to do.



Tom

 

[Tim Singleton]

I have gotten adjustable hangers from Bulletcentral been a while back
not sure if they still carry them

 

[AlNyhus]

If the cocking cam helix is deep enough and the closing cams are designed right timing an action is really basic stuff. When they aren't it's a lot of work and a dremel is not the right tool it has to be done on a mill or it's going to open like sh!t. I have had to fix a lot of dremel jobs. In that case your far better off with cock on close if your not going to do it right.

This ^^^^^^^

Good shootin' -Al

 

[Mulligan]

Sometimes a guy just has to do what a guy has to do.

View attachment 1314445

Tom

What did you learn Tom? Is one better than the others?
inquiring minds want to know.
CW

 

[tom]

What did you learn Tom? Is one better than the others?
inquiring minds want to know.
CW

Yes