Rebuilding a Firing-Pin Tip

Once in awhile, I’ll have a weak moment and allow myself to get roped into a repair where I didn’t ask enough questions before agreeing to take on the job. And, as you know, some of these can be a nightmare. Such was the case with a .22-rimfire bolt-action rifle with a firing pin that wouldn’t hit the case rim hard enough to detonate the primer. The customer described the problem on the phone, and wanted to drop it off the next time he was in the area.

I agreed, mainly because I have a longstanding interest in .22-caliber rimfire rifles. I’ve worked on so many of these rifles in the past, I thought to myself: "How difficult could the job be?" When the rifle arrived, it turned out to be a B-Series Mauser .22-rimfire bolt-action that this customer’s 22 cartridge showing a proper strike to the rim from a firing pin of the correct length. On the right, the strike was too light to detonate the primer (arrow). father had acquired while stationed in Germany with the U.

S. Army. This type of rifle was used as a training weapon during World War II for young infantrymen serving the Wehrmacht. Start by Cleaning The first step I go through when diagnosing any type of ignition failure is to do a thorough cleaning of the firearm. (That’s after I’ve made sure that the action is safe by ensuring that it’s empty.) Then I removed the bolt from the action and completely dismantled it.

All of the bolt components were then scrubbed with cleaning solution to remove the buildup of grime and gunk so that any cracks, chips, or flaws could be easily seen. For parts cleaning, I’ve been using a product called "Jungle Jake" for a little over a year now, and this stuff really does a terrific job on removing grease and gunk. What makes its use even more appealing is that this stuff is one of the "green" cleaners, in that it is water-based and biodegradable.

Unlike with petroleum-based cleaners and solvents, you don’t need to wear protective gloves with this product to prevent harm to your skin. The cost is less that $3 a gallon at your local farm-supply store. Once the parts are given a final rinse with clean hot water, I blow them dry and wipe them down with a protective solvent like Break-Free CLP before reassembly. Now that I had the bolt and striker assembly clean and lightly lubed, the bolt was reassembled and I reinstalled it back into the action.

Then I took the rifle outside to my 25-yard range to see if the cleaning had cured the ignition failure issue. I tried several brands of .22-rimfire ammunition with the same results’no detonation of the primer. To detonate the priming mix of a .22-rimfire cartridge, the firing pin must flatten the rim of the case in the

010 inch over the correct length. area where the firing pin hits. This firing pin did not seem to strike with enough strength to accomplish that important task. I ordered a replacement 14-pound striker spring from Wolff Precision Gunsprings and installed it. When I tested the rifle, the results were the same’ignition failure. Once again, I disassembled the bolt and this time I inspected the firing-pin tip with a 10-power illuminated magnifier.

Under magnification, the firing-pin tip appeared to have been worked on with either a file or a grinder. In all probability, the firing-pin tip had "mushroomed over" from dry firing, and the owner then cleaned up the rounded-over tip, thus creating a situation where the length of the firing pin became too short. Repair Solutions Replacement parts for rifles such as this one are nearly impossible to locate and could run up an incredibly large phone bill.

Sometimes the only practical solution is to either make anew firing pin or put anew tip on the original pin. In this case, I actually did both. Not knowing what type of steel the original firing was made of, or how the original steel would react to the heat from a torch, I decided to first make anew firing pin. The one I made had a front tip a bit longer so it could be adjusted for length later.

Once I had this replacement firing pin as a backup in case the original one melted or became botched up beyond repair, I started making the calculations required to put anew tip on the original firing pin. The tip of the original firing pin would make an impression on the rear face of a .22 cartridge rim that was barely noticeable. Averaging the rim thickness on .22 rimfire cartridges made by Winchester, Federal, Remington and CCI, I came up with a thickness of .040 inch.

The distance from the back face of the striker-spring collar to the current tip on the firing pin measured .626 inch. I then chucked the original firing pin in the lathe and faced the damaged tip back .300 inch to where the radiused shoulder began to blend with the .075-inch front diameter of the firing pin. The diameter at this point measured around .110 inch. Next, I chucked a number "O" center drill in the lathe tailstock drill chuck and used it to create a starting hole for a #52 (.0635 diameter) drill.

The #52 drill was then used to drill a hole to a depth of .240 inch into the front end of the original firing pin. The inside diameter of this .0635inch-diameter hole was then chamfered slightly to accommodate the tiny radius that will be present on the tail of the lathe-turned replacement tip, allowing the replacement tip to fit flush against the face of the original firing pin.

What would eventually be the replacement tip on the original firing pin started out as .125-inch-diameter "stress-proof" steel purchased from Brownells. (The same steel in .375 inch diameter was used to make the duplicate firing pin with a longer tip referenced previously.) This steel is very easy to machine, but is tough enough without heat-treatment to use for making firing pins or assembly pins, so it’s a good material to keep on hand.

The .125-inch-diameter stressproof steel was then turned to a diameter of .110 inch for a length of .350 inch. This part was then reversed in the lathe chuck and then the tail that will be inserted into the original firing pin tip was turned to a diameter of .065 inch for a length of .200 inch. The tail diameter going into the end of the firing pin depends on which type of permanent assembly you wish to accomplish. The assembly I chose involved using hard-solder to bond the joint permanently.

Two other methods that could be used area press-fit or a shrink-fit. Of these two, I would lean toward the shrink-fit to avoid the risk of breaking the little tail off the replacement tip. The shrink fit would involve turning the replacement tail on the new tip to a few ten-thousandths of an inch over the true hole size in the (continued on page 17)

original firing pin. The replacement tip would then be frozen by spraying with a product called "Freeze It," while heating the original firing pin end with the hole in it with a propane torch. The new tip shrinks from freezing while the hole expands from heating, and then the tip is inserted in the hole. Once the temperature of two parts normalizes, you have a very tight bond.

Once the two parts have been permanently fastened together the front end needs to be turned down to a diameter of .075 inch and blended with the 12mm radius just in front of the striker-spring collar. I was careful to avoid cutting into this radius. For this process, a radiused file does a good blending job. Conclusions The exact tip length of this firing pin is a "cut and try" proposition.

Once you get a tip length that puts an impression into the rim of the cartridge case deep enough to detonate the primer, it’s time to end the length trimming. The firing pin will work just fine with the tip diameter left in around state. The original on this rifle had a chisel point with the side angles cut at 20 degrees, so that’s how I tipped this one.

Also, the firing pin on these Mauser B-Series rifles acts as the ejector also, so if the firing pin tip is left too long, premature ejection could cause jams in the action. Your customer should be reminded to avoid dry firing a rimfire rifle, as it will damage the firing pin tip.

Also, to relax the striker tension on an empty chamber when storing these rifles, he only needs to hold the trigger back with the index finger of the left hand while pushing the bolt forward and turning the bolt down and into the forward locked position. Of course, your customer will probably ignore your advice, and eventually will be coming back to you for a replacement firing pin. If you can’t easily locate a replacement pin, you can consider using the procedures outlined here. I