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Different shapes for .22lr firing pin

9.5K views 34 replies 14 participants last post by  maddmatter1970  
#1 ·
Does anyone know, if there is any real advantage for the shape on the head of a firing pin for rimfire in general or .22lr specific?
I ask cause I want to see a titanium firing pin someone is making, and they claim a cresent shape "both has more reliable ignition and less chance of an out of battery ignition "
I kind of think the first pitch may have some truth, but the second one is all wet no matter how I slice it.
Anyway anyone have experience/opinion?
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#10 ·
There are many different shapes of rimfire firing pins from a small round pin to a much larger pin like you see in a 10/22. It's simply a matter of physics .... the larger the surface area of the firing pin tip, the harder the pin must be struck to get positive primer ignition. Newer Ruger revolvers now use a very small diameter firing pin that makes a small but deep dent in the rim. This is good if the priming compound in the rim is evenly distributed but bad if there are voids. I think you could make an argument on either type. Probably one of the best firing pins is in a 10/22. It is chisel shaped and makes a long deep dent in the case's rim. That said, I still get a few failures to fire with cheap bulk grade ammo because of poor priming compound distribution. If I rotate the cartridge about 90 degrees, chances are it will go bang.

The real problem is not so much the shape of the firing pin, it's the quality of rimfire ammo. I would think the crescent shaped firing pin would be the most robust, providing you use a full power hammer spring.
 
#11 ·
FWIW - My Bearcats and SP have a dome shaped tip. The S&W .22 AR is a small chisel tip. Makes a smaller but deeper indent than the Rugers.
 
#13 ·
Randy, Here's a drawing of a 10/22 firing pin. #1 is the tip, #2 is the firing pin spring surface. #3 is the limit slot. #4 is the hammer strike surface. If you shorten the tip, likely you will get failures to fire because a cross pin in the bolt will limit how far the firing pin can travel. The primary purpose of the limit is to prevent damage to the chamber mouth when dry firing. Because the bolt does not automatically lock back after the last round fires, the gun must be safe to dryfire..

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#14 ·
The biggest problem with rimfire reliability is that the anvil (orange arrows) sits at an angle to the strike from the firing pin.
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So the tendency is for the priming mix to be pushed into the center of the case, rather than be held stationary and get pinched against the anvil.

The second biggest problem is the standard rimfire firing pin wastes a lot of energy squashing the thick outer brass rim. The energy arriving at the firing pin is what the mainspring expended, minus losses from friction, abrasion, and other losses due to the design of a particular firearm. So the energy the firing pin gets is pretty limited and it needs to not only push the shell forward to seat against the barrel face, but also press some of the base brass down to the anvil. Deforming the thick outer rim wastes enough of the limited energy to cause a LOT of missfires. People tend to blame the ammo, and I call BS. I average well over 10,000 rounds between missfires - using mostly cheep bulk ammo that other people whine and cry about.

You can't do much about improving the ammo, but there's a lot you can do to improve the quality of the firing pin strikes. Shaping the tip to avoid the thick outer rim is one of the easiest and best ways.

I started down the shaping road by emulating "picture 4" shown in post #12. Well, reliability immediately improved, but accuracy went down the crapper. So I tried a variety of tip shapes (6 or 7) before I determined what the keys are.

1) Hit far enough inside the rim so you "fold" material into the rim - instead of crushing the outer rim. This captures priming for crushing instead of squeezing it out of the pocket.

2) Keep all FP tip surface square to the barrel face. Angled edges will tip/shift the shell and destroy accuracy. At least it does in sporting chambered barrels. Maybe it's less critical in match chambers, but I haven't tested it.

3) Wider FP tips will crush more priming area and make small voids less of an issue. I really wish the rimfire gun makers would offer FPs that have not been narrowed at the tips, so users could make the shape they want.

I'd say the round tip in the OP is "good", my tip (shown below) is "better", and the crescent tip is "best". But I will always prefer a full weight steel FP over lightened up or Titanium FPs. Lighter pins are trading away reliability for a "faster" lock time. I'll take reliability all day.

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#15 ·
I have an old Mossberg auto loading 22 chambered for shorts, longs, and long rifle. It uses an adjustable follower on the mag for the three different chamberings. I did a complete tear down and clean when I bought it used many years ago. The striker/fp is almost exactly the same as the one illustrated in lowegan's post. The pic caught my attention because I had put the part in backwards. The rifle fired, but wouldn't cycle. At the time I thought it was hilarious. IIRC the old gun also lacks a bolt hold open after the last shot.

Interesting thread. I've never disassembled the bolt on my 10-22..
 
#16 ·
My first thought is,
I have learned not to put a lot of stock into claims made by someone trying to sell product.

My believe, the best shape for a rimfire firing pin is one that ignites the primer. :unsure:
While that sounds obvious,
I think the reason that there are different firing pin shapes, is that it may not matter as much as we might think.

I have several .22's and while I have never paid much attention to firing pin shape because they all work,
I did suffer many failure to fires with the surplus M261 .22 adapter for my AR-15's.
When looking at it, I noticed the firing pin was round and it seemed to me that might be the problem.
(I had never noticed a round .22 firing pin before.
I shaved a bit off each side making it kind of rectangle shaped.
No difference at all, I was frustrated.
I don't know how many hours I spent trying super cleaning it, lubrication, a new firing pin, etc.

After all that, and several frustrating range trips,
It turned out, that I was simply using .22 ammo that the adapter did not like.
As soon as i switched to better ammo, presto.... both firing pins (original and my modified) worked fine.

As for titanium firing pins..... I think that is another "gimmicky", "snake oil" product.
But that's just me. :ROFLMAO::LOL:
 
#20 · (Edited)
The GP100-10 has a tiny, rounded firing pin that strikes the very edge of the rim. MY gun hardly ever makes it through a cylinder without a misfire. I've tried different ammo and found Aquila to work much better than CCI, but even that misfires all too often. Yes, I have taken material off of the hammer step, helpful, but not a cure. My Taurus 94 has a chisel shaped firing pin and a lighter trigger pull - it doesn't missfire. I've given up on my GP and bought a Colt King Cobra.
 
#28 ·
It just makes since @maddmatter1970

Rimfire primer is spun into the perimeter of the case. Better ammo is more uniform in primer application I suspect. Your new firing pin crushes more circumference of the shell.

Pretty cool.
yeah it struck me as an actual good idea! so far so good. at this point, I would highly recommend it! with the lighter of the 2 included springs. I can't believe it took me so long to find this solution.