Firing Pin Fall

[Ledd Slinger]

This seems strange, as Kelbly is adamant about having adequate pin fall and static spring pressure on all of their actions.

Somebody has messed with it.

My Lapua size Kelby Atlas was pretty dang close to .240” pin fall straight out of the box, but the trigger timing was way off with my BnA TacSport Pro. Lots of cock on close.
When I got the trigger timed to the cocking piece, the pin fall had been reduced to about .220”, maybe less, can’t remember exactly...Anyhow, I had to re-drill the cocking piece pin hole on the firing pin to get the pin fall back. Now it’s timed to the BnA trigger with .242” pin fall.

so technically it had good pin fall out of the box, but not good trigger timing.

 

[tmwinds]

While we are on the subject of firing pin fall, would a weak firing pin spring replicate the same symptoms as insufficient fall, erratic ignition? I ask because because I have a couple of BAT actions that are 8-10 years old with many thousands of rounds fired and still have the original springs.

 

[Ledd Slinger]

While we are on the subject of firing pin fall, would a weak firing pin spring replicate the same symptoms as insufficient fall, erratic ignition? I ask because because I have a couple of BAT actions that are 8-10 years old with many thousands of rounds fired and still have the original springs.

Yes. It’s good to change your FP springs out every year or two. The springs are always under compression even when de-cocked. It’s a wear part that will weaken with time.
They might last with close to full strength longer than two years but they don’t cost much and this way you know your spring strength is always good.

 

[Ledd Slinger]

I bet a person could buy a simple spring force gauge to keep track of your FP strength over time. Have a bunch of different scales on Amazon. Test a new spring right away to get a baseline and check it however often you want to see if it’s losing strength. Might save you money on new springs or might cost you more money than planned. Would just have to use it and see.

This one seems to have good reviews. Can even buy an arbor press stand with DRO stroke length gauge for it.

 

[NV_Dmax]

This seems strange, as Kelbly is adamant about having adequate pin fall and static spring pressure on all of their actions.

Somebody has messed with it.

wrong.
It was straight from them out of the box brand new.

 

[WSnyder]

My Lapua size Kelby Atlas was pretty dang close to .240” pin fall straight out of the box, but the trigger timing was way off with my BnA TacSport Pro. Lots of cock on close.
When I got the trigger timed to the cocking piece, the pin fall had been reduced to about .220”, maybe less, can’t remember exactly...Anyhow, I had to re-drill the cocking piece pin hole on the firing pin to get the pin fall back. Now it’s timed to the BnA trigger with .242” pin fall.

so technically it had good pin fall out of the box, but not good trigger timing.

Kelbly and almost all others using the Remington design are pretty likely to have cock on close when you set them up with proper pin fall. The only recent exception that I know of is BAT (with the urging of Alex Wheeler). Hopefully Kelbly and others will follow suit someday and extend the cocking ramp helix along with the correct pin length and move forward.

 

[beak]

I have two[2] pandas never have had prob== they have b&a triggers. both are F-class. on other kelb--s they take care of it. steve

 

[BoydAllen]

I have an early Viper with a .062 (nominal) FP tip diameter that came with a .200 fall and a 19# spring....with no problems. As it came, it was timed perfectly for my Jewel HVR (don't ask). Some time later Jerry Stiller told me that I should reverse the trigger bracket to gain additional fall. I did, and it increased the fall to .220. That amount of cock on close is not noticeable unless you are operating the bolt slowly. My only conclusion is that perhaps the small FP tip requires less energy to do its job properly when using relatively sensitive small rifle primers. I mostly shoot 205s, that are seated very solidly.

 

[Dusty Stevens]

I have an early Viper with a .062 (nominal) FP tip diameter that came with a .200 fall and a 19# spring....with no problems. As it came, it was timed perfectly for my Jewel HVR (don't ask). Some time later Jerry Stiller told me that I should reverse the trigger bracket to gain additional fall. I did, and it increased the fall to .220. That amount of cock on close is not noticeable unless you are operating the bolt slowly. My only conclusion is that perhaps the small FP tip requires less energy to do its job properly when using relatively sensitive small rifle primers. I mostly shoot 205s, that are seated very solidly.

The tip shape and size makes all the difference in ignition. Its a thing those in the know dont mention much. Shaping a tip is a roll of 4 of the 10 sided dice

 

[Paw precision]

I have done extensive testing with firing pins and springs to develope my own analysis for yielding the lowest ES and SD's but more importantly to mitigate the ill's of harmonics from pin fall that are prevalent with actions. What i have learned is the pin has to have performance to achieve two demands. First is energy by which the cup has to be overcome with force and the second is the needed minimum speed upon which to set off the primer particles with consistancy. A smaller pin tip can be a great gain, a stronger spring can be a gain - which has its minimum for different makes of actions ( however can lead to unwanted tradeoffs ) - but fall to build speed is a must and the amount of extra spring strength needed to overcome the lack of fall is more than i first believed.