Why Kadets Break the Barrel Retaining Roll Pin

[75Plus]

A thread on light firing pin strikes while using the Federal 550 round bulk pack mentioned the problem of broken barrel retaining roll pins allowing the barrel to move. Since I had had a problem with light strikes I checked my Kadet kit and my full Kadet. The kit had shattered the roll pin. It came out in small pieces once a punch was applied. The roll pin in the full Kadet was still intact.

I made up a temporary solid pin and installed it in the kit. I then measured the gap between the slide and the slide housing and found it to be .018". This meant that the roll pin was stopping the slide .018" BEFORE it could contact the housing. The roll pin was being hammered with each round. Since roll pins are hardened to begin with this constant battering caused them to crystallize and shatter.

I removed the top end from my Kadet and measured the gap on it. A .004" feeler gauge was a snug fit. Not good but at least better than .018" I currently have no plans to correct that gap. The barrel protrusion on both pistols reflected the difference in the gaps with the full Kadet protruding .028" while the kit barrel shows .014".


This is the action I have taken to correct the problem with the kit. I found that the hole through the barrel lug had a .004" taper. It went from .121" to .125". The holes in the slide housing were .121". I had a 1/8" (.125") reamer so I reamed all the way through with it. 1/8" roll pins are readily available should I ever need another one. I considered the reaming necessary as the taper in the barrel lug would have put a strain on the factory pin. I found an old clock spring that miked .018" so I annealed a short piece of it and made a shim to close up the gap between the slide and the slide housing. Now,when the slide is closed, there is just under .001" clearance between the breach face and the end of the barrel. I believe this will close up a bit after a few rounds.

Here are a few pictures showing my findings and solutions.

This shows the difference in the gaps. The kit is on top.



The shim to close the gap.



The shim installed.



A piece of .001" shim stock being firmly held in the breech.

[burley]

Hummm, nice work.  And you're fortunate to have the kit as well as a complete Kadet for compairison.   I don't have that gap on my KK, it seems to mate perfectly.  Perfectly that is until the extractor hits in the slot and holds it out of battery a tiny bit.   I smoothed the slightly peened edges a bit with a diamond file and it may or may not help.  Who knows?   It's going to take live fire to tell and I just cant sit here in my house and test fit a live shell over and over to see how it's going to look.  I guess we'll have to get out and do some shootin' and see how well our 'smithin' is going to work.  Good luck to you 75plus.

 btw, your complete Kadet operates fine and the kit has the light strike problem?



4/27/11   New idea for me, I probably just need a new recoil spring.  Duh, I have as many as 25,000 rounds through by now and my ftfire has been a gradual increase.   Still need to do some shootin to find out .

[joerchi69]

Here are a few pictures showing my findings and solutions.

This shows the difference in the gaps. The kit is on top.
The shim to close the gap.
The shim installed.
A piece of .001" shim stock being firmly held in the breech.
[/quote]

Because those fotos are gone (or just invicible) i would like to ask someone with that modification to show what is meant. Because it is not clear to me..
I ' am dealing with light strikes quite a while and like to make sure to understand what gap and where to measure in a shim.

[painter]

Maybe pm 75Plus. He might still have the pics.

[Joe L]

75Plus will remember the details about this.  I can tell you that the barrel retaining pin will still fracture over time, regardless of any shimming.  I had 3 failures in 50k rounds.  My solution is to just replace the pin once/year with a fresh one.  Takes 5 minutes and won't change the zero.  You will know it is broken when the gun suddenly starts shooting a foot high at 25 yards.  I just drilled my slide and barrel out to 1/8" and use good quality tension pins. 

Joe

[joerchi69]

I think that is the gap to measure and to fill with spacing ?



Tryed to size / combine it, to have the same time contact of slide to "upper" (area 1),
and contact area over breech face to barrel (area2) .  I am not a native english writer. Help with gunsmith nomenclature is very much appreciated..

Rough-and-ready spacers, survived testing.


same time contact area 1


same time contact area 2