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Posted: 1/30/2006 5:36:32 PM EDT
My Ciener conversion kit firing finally broke after more than 6K rounds. I had heard of replacing the pin with one made from an AR pin. So I thought I'd try to do just that.
Well that AR pin is some damn hard material. After turning the collar down and cutting the OAL a bit it was time to turn the end (where the spring goes) that sticks thru the bolt to the proper diameter. Can't easily do it on a lathe so we made a collar to hold the pin and placed it in an spin indexing fixture. Set it up on the milling machine and ground the little sucker.
Cut it to length and ground the tip profile and retainer pin notch by hand with a Dremel.
I'm happy to report it worked and digested 700 rounds FA in one afternoon.
Even an AR pin with the tip broken off is still long enough to convert so now you have a use for them.
Would appreciate hearing tips & tricks as to how others have made theirs.
Link Posted: 1/31/2006 8:44:40 AM EDT
I picked up a pin the other day and was going to go for it very soon. I'll let you know what I find. I suspect the metallurgy of the various makers' pins varies, maybe you got a really hard one.

One option might be to draw the temper slightly, which would be easy if we knew what the alloy was. If it's air-hardening, it'll withstand higher temps than, say, oil hardening stock. I'm thinking a slightly softer pin would last longer and break less frequently than the stock.
Link Posted: 1/31/2006 12:00:42 PM EDT
Good report! But we'll need pics of your RIG!
Link Posted: 1/31/2006 1:29:46 PM EDT
Can't do pic's sorry. You can find the spin index jigs on line to see what they look like. The one I used was a cheap $50 rig and worked well enough for this job.
I'll have a few more broken AR firing pins to machine in a few weeks via a friend. I'll let you guys know if I can tell a difference in hardness/temper between any of them.
Link Posted: 1/31/2006 6:09:20 PM EDT
My stock pin only ran about 1000 rounds before it broke. I had both of the parts so I had something to measure.
I don't have a lathe but I stuck the m16 pin in a drill press and wacked away at it with a dremel,kind of crude but the uggly sucker has run fine for about 4 or 5000 rounds since then. All I have to run is a ar15's so only semi for me. I was thinking at the time that it was pretty tough going. The pin I used was a DPMS spare that I had in my parts and pieces box. I should order a spare Ceiner and then my ugly repair would likely last forever. It iritates me to have to spend $10 to ship a part that could be slipped in a envelope with a $0.39 stamp. I just wish some machine shop would set up and crank out a bunch of these pins so us poor slobs could order them over the net with a credit card when we needed them instead of fighting with JAC.
Link Posted: 2/2/2006 2:22:01 AM EDT
You can get a spare firing pin from Kuehl precision firearms ( http://www.kuehlprecisionfirearms.com/ )

for 10$ + 2$ shipping.


My stock pin broke after a few hundred rounds. :(
Link Posted: 2/2/2006 7:34:49 AM EDT

Originally Posted By Gorilla:
One option might be to draw the temper slightly, which would be easy if we knew what the alloy was. If it's air-hardening, it'll withstand higher temps than, say, oil hardening stock. I'm thinking a slightly softer pin would last longer and break less frequently than the stock.


Of the AR pin or the Ciener pin? The AR pin alloy might be specified in the AR blueprint package if someone has access to that.

My Ciener pin hasn't broken yet. I'm probably close to 2k rounds now. I ordered a spare from Kuehl along with a barrel and some other parts so mine will probably never break...

Do the Ciener pins break because of a weak spot? Or are they just poorly heat treated or something? If the latter, would it be possible to re-treat the original pin. Blow torch and a bucket of old motor oil? I'm assuming water quench would be too brittle.
Link Posted: 2/3/2006 6:23:24 AM EDT

Originally Posted By Mike_L:

Originally Posted By Gorilla:
One option might be to draw the temper slightly, which would be easy if we knew what the alloy was. If it's air-hardening, it'll withstand higher temps than, say, oil hardening stock. I'm thinking a slightly softer pin would last longer and break less frequently than the stock.


Of the AR pin or the Ciener pin? The AR pin alloy might be specified in the AR blueprint package if someone has access to that.

My Ciener pin hasn't broken yet. I'm probably close to 2k rounds now. I ordered a spare from Kuehl along with a barrel and some other parts so mine will probably never break...

Do the Ciener pins break because of a weak spot? Or are they just poorly heat treated or something? If the latter, would it be possible to re-treat the original pin. Blow torch and a bucket of old motor oil? I'm assuming water quench would be too brittle.



Mike, I'm thinking if the stock Ciener pin breaks (mine hasn't yet) it's indicating an overly hard condition. If the metal was softer, it'd probably deform rather than fracture. Somewhere between soft (deformation) and hard (fracture) is the "sweet spot".

As far as alloys go, I'd say A2 would be ideal. It's expensive compared to most others, but worth it IMO. I need to get into my Machinery's Handbook and do some comparison shopping. They usually discuss the typical applications for their tool steel alloys section, and while firing pin won't be there, I'd bet if it says something like "A2 is ideal for dies, punches, etc" it'd work great. Punches take shock without fracture or deformation.

As far as re-treating an unused Ciener pin, if we knew the exact alloy, and how it was heat treated at the factory, it'd be relatively easy to draw the temper just a bit more prior to use. If it's carbon steel, you could even do it in a toaster oven. If it's A2 or some other high-end alloy, the tempering requirement might be above 500 f. which is the limit of most home ovens. I do have a little computerized shop furnace which will do the job, I just need to get off my ass and play with this a bit.
Link Posted: 2/3/2006 6:47:45 AM EDT

Originally Posted By Gorilla:
Mike, I'm thinking if the stock Ciener pin breaks (mine hasn't yet) it's indicating an overly hard condition.
...
As far as re-treating an unused Ciener pin, if we knew the exact alloy, and how it was heat treated at the factory, it'd be relatively easy to draw the temper just a bit more prior to use. If it's carbon steel, you could even do it in a toaster oven. If it's A2 or some other high-end alloy, the tempering requirement might be above 500 f. which is the limit of most home ovens. ...


Mine hasn't broken yet, so I don't know the failure mode. (I'm also not a mechanical engineer so my knowledge of steel is a bit limited, but I knew enough MEs in college to pick up a little.) I'm going to take "broken" to mean fracture, so let's go with too hard. We don't know if it's a fatigue failure, or a single-incident break. Could it be work-hardening to a brittle state from repeated impacts? Would that come from it being too soft to start with, so hardening would help?

I'm gonna guess that there's no high-end alloys in the Ciener kits. My recollection of re-profiling the broken tip of the extractor and modifying the receiver plate for a Kuehl barrel were that both filed down pretty easy. Easier than getting through the anodizing on the upper recieiver I fitted I think. I'd guess the FP is made from the same stuff, but may be heat-treated differently. Or maybe none of it is?

Assuming he is heat-treating the pins, let's guess that he's going too hard/brittle. Oil-quench is less brittle than water-quench, right? I was thinking if you re-treated it with an oil quench that would give you a good hardness. But you're suggesting tempering back from his hardness with a lower temp reheat?
Link Posted: 2/4/2006 6:44:11 AM EDT
I agree the pin is probably plain carbon steel, hardened and then tempered. If this is the case, all you need to do is re-temper.

[professor hat]

The process goes like this for basic steel heat treatment - The steel is taken above its transformation temperature, usually a dull red. The standard home smith trick is to slowly heat it until a magnet no longer sticks. For maximum effect, you'd need to hold it there for upwards of a couple of minutes for a firing pin, but if necessary you can quench immediately. The FASTER the temp is dropped, the HARDER the resultant steel. Old timers used to quench in icy brine for maximum hardness, or even mercury, which can kill you, so that's a bad idea. But warpage with severe quenching may occur and this depends upon the alloy.

Oil quench is probably the safest. Once quenched, the steel is dead hard and a file should squeak off and not touch it. Think of it like glass, hard but brittle. Tempering is next. Tempering takes the glassy hard steel and turns it into a tool. It's nothing more than heating the metal to perhaps 300 to 600 degrees f. and then letting it cool. The higher the tempering, the softer it becomes, and the more shock resistant.

What this means is if the Ciener pin was tempered at 400 degrees, and we re-temper to 500 degrees, it'll become slightly softer and more shock resistant. If you go too far and it becomes too soft, you must repeat the entire cycle, which is not good, as a piece of steel the size of the pin will oxidize and flake at transformation temps. The use of a borosilicate glass powder like KeepBryte will prevent all oxidation.

That's why I like A2 steel, which is quenched in "air". The parts are wrapped in stainless foil, avoiding all oxidation, heated, and the whole foil pack is simply set out on an iron block to cool. It is then tempered like plain carbon steel, except the required tempering temps are much higher.

To mass produce Ciener pins, I'd preferably go with a handful of stock M-16 pins. Anneal the batch, avoiding oxidation. They'll be soft and can be turned and milled. Then, the whole bunch would be re-heat treated and annealed to probably somewhere near spring temper, plenty hard for a .22 and durable to boot.

[/professor hat]
Link Posted: 2/4/2006 8:57:24 AM EDT
Thanks Gorilla.

I like to stimulate my mind every once in a while.

My last job delt with a lot of metal fabrication and engineering. Now I work for a much larger company, and I don't have a chance to do that much at all.
Link Posted: 2/5/2006 7:32:38 AM EDT
i had a Ciener pin brake on one of my 22 kits he replaced mine for free mine broke at the roll pin that holds it in the 22 kit i put an average of 1500 to 2000 rounds a weakend i eus the cheap federal stuff from walmart
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