[boing]

Broke the rear end off the firing pin on my P11. Pretty discouraging at first, because the gun has performed so well to date, and even though I don't have any snap caps, I haven't really dry fired it much at all.

But upon removing the firing pin and examining it's range of motion, I can see how the presence of a cartridge against the breechface keeps the cut-out in the pin from slamming into the retaining screw. It just isn't designed to go that far and withstand the impact stress in the location.

Operator error. :o

I'll be calling Kel-Tec tomorrow, and getting some snap caps at the shop when I go to pick up my reloading components.

Sigh.

[Blackhawk]

I'll be interested to see what Cliff says, but your theory sounds plausible IF the FP had a metallurgical flaw from the git go.

I use snap caps anyway, but your experience is a new one to me!

Please post a follow-up about what Cliff says. :D

[Tropical Z]

This is one of the mysteries of the ages.For everyone who says use snap caps in a Kel-Tec,theres someone else who swears theyve dry fired theirs thousands of times without one.I know of no other similar gun.

[Blackhawk]

TZ,

The KT manual says "don't dry fire" or something like that I think, but since they use machined 4140 steel for the FP, I haven't understood why. Boing may have discovered a reason if the hardening was uneven leaving the FP stressed. The set screw is much harder than the FP, but the cross sectional area where boing described the break should be able to handle the FP being repeatedly slammed into the set screw.

However, that doesn't happen if the set screw is adjusted properly, and I don't think it can if the set screw is too tight. The hammer is wider than the back of the FP so the slide stops the hammer before the FP gets anywhere near the set screw. The set screw's only purpose is to keep the FP in place.

I've dry fired mine thousands of times with snap caps but also many times without. I don't really understand how boing's problem could occur, and that's why I'm really interested in what Cliff has to say.

[boing]

Just spoke to Cliff. He said dry firing is the cause. I scanned through the manual looking for the dry-firing warning, but couldn't find it at first. Whoops, there it is, on page 13. Doh.

Anyway, a new part is on the way, free of charge despite operator incompetence. He sounds like a busy guy. With people like me out there, it's no wonder. :D

The hammer is wider than the back of the FP so the slide stops the hammer before the FP gets anywhere near the set screw.

But inertia carries the FP into the primer, and with no case to stop the FP from going forward, the pin just sails along until it smacks into the set screw. The FP spring is pretty stiff, but it has to allow the pin go forward with enough force to detonate the primer. I imagine there's extra inertia built into the system, possibly enough to send the FP that far forward.

Maybe it was just a bad part. I dunno.

[SteveA]

Interesting. Anyone know of any other modern center fire arms maker that warns against dry firing?

I'm questioning the quality of the P11. A friend - who has NOT been dry firing his P11 called yesterday and they're sending him a new extractor and springs for it. He shot that gun 3 times [rounds] last week with me and the extractor, just behind the roll pin, broke.

Not a good example. They're replacing the parts for him but that - combined with a broken firing pin due to dry firing leaves me concerned that when it's most needed for personal protection - it may fail.

Not good.

[Blackhawk]

But inertia carries the FP into the primer, and with no case to stop the FP from going forward, the pin just sails along until it smacks into the set screw. The FP spring is pretty stiff, but it has to allow the pin go forward with enough force to detonate the primer. I imagine there's extra inertia built into the system, possibly enough to send the FP that far forward.
The FP only weighs about 1/10 ounce and the FP spring has resistance of about 8 pounds. There's no way that inertia is going to carry the FP any measurable distance once the hammer hits the slide.

I just disassembled my P-11 to measure how far the FP "overtravels" the hammer before being stopped by the set screw or compressed spring. It's about 0.50", and there's absolutely no way inertia could carry it that far or it having enough energy to do any harm.

I think you had a bad part.

[boing]

Well, I'll defer to your knowledge of the physics involved, but here are my observations.

1) When pushing the firing pin all the way into the slide, the firing pin spring doesn't stack soon enough to stop the rear of the firing pin from contacting the screw.

2) The part of the pin that broke off (the rear of the cut-out notch)shows a wear pattern consistent with impact against the screw. A similar wear pattern is evident on the front of the cut-out notch, where we know the screw makes contact.

3) The end of the screw itself shows wear (deformation) at two points, 180º from each other, indicating that the screw is being hit from both the front and the rear.

The screw has never been adjusted since I bought the gun, NIB.

Based on what I see, and ignorant of what the physics suggest should be happening, my opinion is that dry firing the gun has thrown the firing pin forward against the set screw, stressing the part in a manner inconsistent with it's design.

I dunno. Maybe you forgot to carry the "1". ;)

I'll take a careful look at the new pin before I install it. I'll shoot it a bunch, and dry-fire with a snap cap, and never let the hammer fall on an empty chamber. After awhile I'll take the pin out and look for any tell tale signs of wear.

[Blackhawk]

Very interesting, boing.

I think you've uncovered a problem with KTs. I only have one P-11, so I don't want to generalize about them.

If MY FP set screw hole were just a bit more than 0.050" aft of where it is, the FP would be driven into the screw when dry firing.

How possible is that kind of manufacturing error? Pretty significant, I'd guess because I saw a P-11 slide that had the recoil spring guide hole drilled 0.34" off center. When the slide was locked open, the guide pointed significantly to the right. While the slides are made from bar stock on CNC machines, I'll bet that there's a lot of human involvement in finishing them.

Just for fun, I took my P-11 apart again and tightened the FP set screw as tight as possible but still letting the FP travel. The FP STILL went about 0.050" into the slide making the FP immune to dry fire damage.

FYI, the distance from the breech face to the center of the set screw hole on my P-11 slide is 1.445" and I suspect it was detailed at 1.450". If your slide has that dimension much greater than that, I'd exchange it. I'd also exchange the slide if the new FP can't overtravel when the hammer hits the slide.

Manufacturing screwups can defeat good designs every time!

[boing]

Set screw hole on mine also measures 1.445 from the breechface.

Interesting.

[Blackhawk]

Downright confusing! :confused:

Guess I'm going to be making a pest out of myself wanting to strip and measure the FP travel of every P-11 I see. :(

[bad_dad_brad]

The Kel Tec P32 can not be dry fired as well. Trouble is, .32 snap caps are kinda scarce. Same deal with the Beretta Jetfire in .25. The Jetfire manual says practice dry firing on a spent cartridge. It is all about that inertial firing pin.

[sm]

I'd be interested in seeing pics and/or drawings of this problem.

I personally have a 6K rd count, I do use snap caps.
I have friends that do not use snap caps, and have not encountered a problem.

Interesting, thanks for sharing.

[yzguy]

ok I hate to disagree with Blackhawk, but the firing pin does travel past where the hammer pushes it....

I first looked closely at how far the pin travels after it is flush with the rear of the slide. I tried to measure it, but could not get a good angle to get in there with the calipers I have, but the best measurement I could get shows that the pin would only have to move .014 inches past flush with the rear of the slide for the pin to contact the firing pin set screw. Now this will change depending on how far you back out the set screw from bottoming out (because the cut out in the FP is curved a bit). The more you back it out the more the FP has to travel to hit it, but also the less metal that it is contacting on the FP to stop it's forward motion (easier to break).

Now to how I proved this...

First, remove the FP, and degrease the rear portion inside the cut out (where the set screw would hit if it were to stop the forward travel of the FP). Then I put a small piece of Masking tape in that cut out in the rear. The I reinserted the FP and backed out the set screw 1/2 turn (being careful not to push the FP in past flush while inserting it, by using a punch that is bigger than the FP hole in the slide). Then fired more than 20 times with a snap cap (only counted 20 but fired 5-10 before I started counting). Then I removed it again and inspected the tape, it looked like this:
http://www.1bad69.com/gallery/GunStuff/kel-tec/dcp03408.jpg

Then I I put it back in and dry fired 5 times with nothing in the chamber and pulled the pin out and the tape looked like this:
http://www.1bad69.com/gallery/GunStuff/kel-tec/dcp03409.jpg

The flash masks it a little but there is a definite mark on it from the set screw.

I am now 100% convinced that the set screw is what abruptly stops the FPs forward movement when dry firing without a snap cap.

[Blackhawk]

ok I hate to disagree with Blackhawk, but the firing pin does travel past where the hammer pushes it....
That's not disagreeing with me. Mine can travel 0.050" past where the hammer stops from hitting the slide. But it doesn't from any inertia imparted to it by the hammer.

But if you're saying that the 1/10 ounce FP keeps sailing on against that 8# FP spring after the hammer disengages and with enough force to break the FP after hitting the set screw if it doesn't contact a soft, thin brass primer cup first, then yes we disagree.

[yzguy]

I have no idea how hard it hits, but would say that if you backed out the set screw a bit far (say maybe a whole turn instead of 1/2) that it would only contact the tip of the rear of the cut out on the FP, which would not take much force to break off (not much metal there) and cause a malfunction....

I thought you were saying that the FP stops dead when the hammer does... It does continue to travel forward hitting the set screw after the hammer stops...

I have seen that it travels at least as far as to contact the set screw, but no clue as to with what force (but does not at all with a snap cap). True it may just tap it....

oh and
Mine can travel 0.50" past where the hammer stops from hitting the slide.
I think something is off with your measurement (typo? maybe .05"??) My FP can't travel 1/2" total with the set screw in, much less past where the hammer stops.... :)

[Blackhawk]

Yeah, typo. Should have been 0.050". :o

[boing]

I'd be interested in seeing pics and/or drawings of this problem.

OK. :)

http://www.thehighroad.org/attachment.php?s=&attachmentid=1704


I've added the black bar to give an approximate(!) indication of where the set screw is located, except it butts up against the front of the firing pin cut-out notch.

The broken bit is about how much protrudes from the firing pin channel when the slide is assembled, and measures about 0.100".

[sm]

Thanks, great pic.

Thanks to the rest of you, I'm learning something...

[cratz2]

I guess I'll be the guy that says he's never had a problem. The first P32 I bought, I probably dry fired it 500 times on the way home from the store. No problems. I gave that one away as a gift to a family member. I've since bought two more, one specifically as a gift and the other for myself to replace the original. I dry fired the gift one probably 100 times, put 200 rounds through it, cleaned it and gave it away. No problems. My current P32 has probably been dry fired over 2,000 or 3,000 times along with about 800 rounds and have has zero failures of any kind.

As much as I like the KelTec pistols, they just can't possibly have 100% quality control of all parts and assembly. Some will break with 3 shots fired while others will last forever. Luck of the draw, I suppose. As long as the company stands behind their product... Of course, if the manual says to use a snapcap, I'd use a snap cap. ;)

[boing]

Regarding forward impact of the firing pin against the set screw, Blackhawk said in his second post:

...that doesn't happen if the set screw is adjusted properly, and I don't think it can if the set screw is too tight.

This may be the problem: the screw is too tight.

The impact marks on the set screw are located on the threads, not on the tapered tip that protrudes below the threads. The threaded part of the set screw has a greater diameter than the tapered tip, so if the screw is turned in too far, the threads come down far enough to interfere with the firing pin's forward range of motion.

Backing the screw out until only the narrow tapered tip sticks into the firing pin channel would allow the firing pin a greater range of forward movement, possibly enough to allow the firing pin spring (by way of resistance or spring stack) to stop the firing pin, instead of impact against the set screw threads.

Also, wear is evident on the "floor" of the firing pin cut-out notch, and on the tip of the set screw, indicating that the tip of the screw was bottomed out against the firing pin during assembly. There is no wear on the top of the firing pin forward of the cut-out notch, so the set screw has been turned in far enough to keep the pin from rubbing along the top of the firing pin channel.

Variations in the seating depth of the set screw would account for the different experiences KT owners have with respect to dry fire and firing pin breakage.

It would appear that my set screw was either bottomed out against the firing pin and then backed off just enough to allow the firing pin to move, or it was simply turned in a good ways and ended up where it did by coincidence.

The million billion dollar question is: How far is the set screw supposed to be turned by the assembly techs at the factory?

And for those of you adjusting your set screws at home, how do you determine the correct seating depth for the screw when you re-install it?

Edit: I guess this would adjust it pretty well: look down the FP channel and turn in the screw until the tip sticks out "just enough", back off the screw one turn, install pin/spring, turn the screw in one turn, done.

[boing]

Of course, if the manual says to use a snap cap, I'd use a snap cap.

Yeah, yeah... :D

[sm]

You mean your supposed to read the manual??

I was told by my longtime friend and gunsmith..."manuals are to keep the gun and stuff from rattlin' 'round the box...:D

[yzguy]

I'm pretty sure that this does not apply to the P-32....

as the firing pin cut out has no "back" part of it to hit the set screw

http://www.goldenloki.com/guns/keltec/f6.jpg
taken from here (http://www.goldenloki.com/guns/keltec/prep2.htm)

I'll have to go home and check my P-32 to see if the rear portion of the FP is round or only half moon....

[Blackhawk]

Boing,

You've touched on a mother lode of valuable P-11 information, and I think you've analyzed the problem correctly!And for those of you adjusting your set screws at home, how do you determine the correct seating depth for the screw when you re-install it?
That's the key question. When I first disassembled mine, I used the old trick of tightening it until it stopped to measure where it was set from the factory. It was 1/4 turn out from bottoming, so that's what I've been using. Somebody else said back it off 1/2 turn.

But the ONLY purpose of the screw is to keep the FP from zinging to parts unknown after the hammer gets out of the way, so there's no reason to have it screwed in more than necessary.

The manual says "factory adjusted" so don't mess with it. Cliff should send factory instructions or tell you how to set it, and I'd sure be interested to know!

Meanwhile, I'm going to adjust mine the way you said!

BTW, don't bypass the Loctite application on the set screw. If it backs out while firing, your gun will be useless and you might get a FP stuck in your face!

VERY WELL DONE, boing! :D :D :D :D

[boing]

Yes, I'm quite awesome. :D

Thanks for the pic of the P32 pin, yzguy. I'm not sure why the P11 would need a rear portion on the firing pin, while the P32 gets away without having one.

I'll definitely be using Loc-Tite. I caught the firing pin square in the lens of my prescription safety glasses last night. I don't care to repeat that experience.
:cool: <--- safety glasses!

Based on the factory adjustment of your set screw, Blackhawk, I'm going to say that my screw was adjusted properly, and not turned in too far. While backing out the screw as I described may prevent the firing pin from hitting the threads when dry-firing, it seems clear that using a snap cap will prevent such impact.

It should be noted that while backing out the screw will allow more room for the firing pin to go forward, it will also allow the pin to sit a little further back under the pressure from the firing pin spring. I don't know if that will have any measurable effect on the dynamics of the hammer/firing pin relationship. I suspect not, but I thought I'd mention it anyway.

[Blackhawk]

It should be noted that while backing out the screw will allow more room for the firing pin to go forward, it will also allow the pin to sit a little further back under the pressure from the firing pin spring.Excellent point!