My Kadet experiment

[painter]

As we all know, most people have issues with light hammer springs in pistols running a Kadet kit. There is a thread floating around where the gentleman did some modifications to his firing pin retaining plate, with good results, and he was able to run a 13lb hammer spring with only the occasional light strike.

I use my Kadet for a bullseye gallery league, and light strikes aren't an option so I've been running a 17lg spring with 100% reliability. I still need to clean the feed ramp and breech face every ~400 rounds to keep the wax buildup from the CCI SV from causing issues. The 17lb spring does make it harder, for me anyway, to keep the gun still when breaking the shot so I've been looking for ways to maintain reliability with the 13lb spring.

Here's what I came up with. I spend some time over at RFC, and those guys are rimfire benchrest freaks. They come up with all kinds of tweaks to maximize every part of rimfire accuracy. One of the tweaks made sense, even to a simple painter. Why use spring energy to crush the very outside of the rim where there is no primer? A stronger spring creates vibration which can cause gun movement, even in a rest. So what they do is modify the striker, or firing pin, so it doesn't hit the very edge of the case and allows the use of a weaker spring while maintaining consistent ignition. In a pistol all I care about is creating the easiest trigger pull and still have it go bang.

What you're looking to do is go from this...


To this...


Pictures were borrowed from a post on RFC.

So far I have about 160 rounds through it with not a single light strike, and I'm running a 13lb spring. This is with two different kinds of ammo. CCI SV and some S&B surplus ammo that came from Czeckpoint that hasn't been 100% even with the 17lb spring. If I can get to the 400 round mark with no failures I'll call it a success.

I'll keep you all posted.

[cntrydawwwg]

Very interesting. So how was this achieved? I would guess a slight angle on the FP? Not enough to shorten obviously, but just enough to keep it from hitting the outer rim?
   Also what other mods are on the pistol? Just curious. Hope you make it past the 400 hundred mark. And if you do, hope CZ has enough FP for replacements, for those of us that will probably screw up this mod. Like me. [emoji87]

[painter]

That's exactly what you do. The edge of the pin that needs to be relieved is opposite of the one that's already angled. Mimic it and then round it up a little. Those guys can get really anal about tip shapes, but I'm not sure if it's really critical for my purpose. The thickness of a .22 case is roughly .010, so you only need to be in that far...maybe a few thou more. I may go a little more on mine. Go slow. It doesn't take much, and radius all the edges very slightly so you don't turn the pin into a 'cutter' and pierce the case. I used a diamond file. The firing pin impression won't likely be as deep as in the photos with a 13lb spring as they are from a CZ rifle, mine isn't, but I'm getting reliable results, so far.

My gun has a bunch of mods. CGW race hammer (including pins) and sear, trigger pin and spring, 13lb hammer spring, a CGW Kadet light firing pin spring (now discontinued), and it's an early Combat so it came with the old style Combat trigger. I also run a red dot with a Springer mount. I shoot bullseye fairly poorly. I'm not as committed to excellence as is Joe L.

...and for the record...

I bought a spare pin when CZ had the Christmas 15% off sale...and I ended up throwing it away. We're all only human, after all.

[Joe L]

So, what this looks like is that, instead of wasting the energy to crush the edge of the rim, where the fold is, just relieve the pin slightly so that you crush the primer just inside the fold, then you can reduce the hammer spring weight and still keep the pressure on the flat part roughly the same.  Obviously, it works. 

I'm thinking it is going to come down to tolerances of the ammo versus the firing pin channel.  If it won't work in some guns, it might be because the pin doesn't hit the same spot on the rim each shot. The tighter the firing pin channel and hole, the more likely it is that this will work. 

Then there is the ammo itself.  I don't have a clue how consistent the case and rim dimensions are, but any variation here may affect how reliable this modification is. 

I think I'll try it, too.  If I can fiind a spare firing pin.  And I need to check a bunch of ejected casings and just see how consistent my current setup is now.  If it isn't consistent right now as to where it hits on the rim, I'll leave it alone.  If it is, then I will try it.  I will need some spent casings to check the hits while modifying the firing pin anyway. 

Painter--thanks for taking the time and effort to try to figure out how to do this.  I don't need the modification myself, as my 75B is set up for SAO, but this is the one thing that drives most CZ run and gunners mad--having to change hammer springs so they can practice with their Kadet instead of  just shooting it like they would in a match.  Really ticks them off. 

This modification is worth some trial and error to refine. 

Joe

[painter]

Joe,

I think I might try to modify the extended pin I got from David. That will allow a little more customization of the pin footprint, and also the length. I might be able to get a deeper strike without hitting the chamber. The other thing the benchrest guys like to do is angle the tip of the pin so the edge near the center of the case hits first. Using David's pin would allow that. If you had a lathe you could modify the tip and then machine the pin stop back as necessary on a stock pin.

Yes, 22 ammo does vary, but I'm using 2 flavors and the pin hits inside the edge on both. We're looking for ignition, not the last .005 of accuracy...

at least I'm not.

[painter]

I got a pm asking for pictures of the firing pin itself and explained I didn't want to take the gun apart yet and would post a pic of some fired cases, so here is that picture...



Joe L mentioned ammo variances, and if you notice in the pic it's obvious the S&B ammo, on the right, has a larger rim OD as evidenced by the position of the hit. That was the ammo I was using to gauge my progress when filing the pin. I will have to go back in and take some more off the pin because I had a light strike on round #201 tonight with a CCI round. It was rapid fire but I was able to re-cock the hammer and the round fired.

Stay tuned...I'm not giving up on this idea yet. I will take a picture of the pin this time. I'll just have to start the test over.

[steerclr]

Awesome post.  Worth trying.

[cntrydawwwg]

Subscribed and living vicariously thru you painter since I don't have time to tinker[emoji2]

[DenStinett]

I wonder if you could grind a flat on the opposite side and just turn the Pin 180^o ?

[Noypi2]

I may try to do this....


Sent from my iPad using Tapatalk

[painter]

I wonder if you could grind a flat on the opposite side and just turn the Pin 180^o ?

Maybe, but I'm not sure where everything would 'land'. The other thing would be with two flats on the pin...

which way do you put it in?

[K3JB]

Thanks Painter, a interesting post. I am running my Kadet on a stock PO-1 and do not have any issues with ammo.
I use CCI sv, it has been very reliable. I have run a lot of 9mm through the PO-1 prior to placing a Kadet on it.
My thought was to change back and forth with the 9mm and Kadet. This is not happening, am using it only with the
Kadet because it works so well. Very smooth shooting pistol, I am not a bull's eye shooter.

[DenStinett]

I wonder if you could grind a flat on the opposite side and just turn the Pin 180^o ?

Maybe, but I'm not sure where everything would 'land'. The other thing would be with two flats on the pin...

which way do you put it in?

The Bevel would then be on the outside and the "Point" would then be more toward the center of the Rim, not the edge
If you were to mark the original Flat with (say) a T (for Top), a U (for Up) or just and X

[painter]

I wonder if you could grind a flat on the opposite side and just turn the Pin 180^o ?

Maybe, but I'm not sure where everything would 'land'. The other thing would be with two flats on the pin...

which way do you put it in?

The Bevel would then be on the outside and the "Point" would then be more toward the center of the Rim, not the edge
If you were to mark the original Flat with (say) a T (for Top), a U (for Up) or just and X

Like I said, it might work, or you still might have to alter the tip not knowing where the strike would occur.

Try it and get back to me.

[DenStinett]

Don't run a lite Hammer Spring, so i couldn't even test the results

Has an issue with my "Super" SP101 and its wmr Cylinder the other day
We were seeing about 75% FTFire with the wmr, but 100% with the lr Cylinder
I think it may be the Reduced Power Hammer Spring I had in it
Switched back to the OEM Spring and the Dimples on the Snap Caps look a lot better
We'll get it out to the "Range" and give the wmr Cylinder another go