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Discussion Starter · #1 ·
I broke my rifle down this morning and noticed the firing pin has wear on it. I would assume it came from making contact with the safety bridge. Is this normal?





I've already put the rifle back together and I prefer not to take it out to replace since it's glass bedded. Of course, if it's a safety issue, I'll do so.

Thanks.
 

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Looks like the chrome is flaking off. Is it gi or aftermarket?

May be bad plating job.

You can remove bolt without breaking down rifle.
 

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Discussion Starter · #4 ·
Not sure if it's GI or aftermarket. Came on a 1997 SAI rifle but everything else, including the bolt has been USGI. I did not know I could remove the bolt without breaking rifle down.
 

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Discussion Starter · #5 ·
After looking at the pin a little more. It looks like wear from making contact with the safety bridge. I didn't think they made contact normally? Should I be concerned about an out of battery discharge? Thanks.
 

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My SAI has the same wear. I assume it's from an improperly formed safety bridge but it passes the tilt test and the firing pin won't move forward until the bolt is fully rotated. I plan on having Ted have a look-see when I can make it out his way.

I won't bother replacing the firing pin until the bridge is checked otherwise a new one will wear just like my old one.
 

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The ubiquitous receiver bridge malformation. Seems all of the mfg's are guilty.

Not good for the pin life if the pin hits the bridge before the bolt hits the back end of the barrel when unloaded. I got in there and ground the bridge angle/ramp. Bolt is supposed to hit the cartridge to stop forward travel. Empty chamber, bolt hits ass end of barrel. NOT the skinny little firing pin.

The ramp and FP tail are there to retract the pin on bolt opening NOT to prevent early hammer strikes.

There is another thread on it, lately, I think I started it. Search for <casebro bridge>?
 

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Discussion Starter · #11 ·
Safety bridge looks ok, didn't see anything abnormal on it.
 

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From underneath, you can measure the length from front of receiver to rear of bridge with calipers. Mine was too long by .020".
 

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I have a firing pin that looks pretty close to that. It is a HR chrome pin, HR bolt, SA double lug receiver. I just bought this rifle and have not much history on it. I have spare pins, both chrome and park. I tought about swapping out with a park pin and see what happens. Any advise? What should I look for on the receiver?
 

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I'm not an expert, just a studier of things that make me curious.

My lowest-possible-tech inspection would be to unhook op rod from bolt, move bolt forward without allowing it to turn, straight across the lug gap. Bolt should hit the ass end of the barrel before the pin tail hits the receiver bridge.

Slightly higher tech- use dial caliper to measure length from front of receiver to rear of bridge. My prints say 3.925 - 3.935". Bridge thickness should be about .150 per the print. My own Federal Ordnance bridge was thick, about .020 each side. I liked that, but the pin tail hit first, was wearing the pin. And, the pins that break the tails off, must be from only this.

I went ahead and used a Foredom tool to grind my ramp bevel deeper/longer by that .020. I wasn't worried about voiding the guarantee from a company that has been out of business for 20 years. Now, bolt against rear face of the barrel, I can wiggle my tail. ;^)
 

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My 80's, and early 90's SA match rifles show similiar wear on firing pin tangs. I don't see such wear on Garands so I assume the SA receiver bridges have a rough surface finish.

I installed a chromed firing pin as the original non chromed had excessive wear. The chromed firing pin has been through one barrel, it is looking ratty.

I am not going to mess with the receiver bridge I will replace firing pins when they break or wear out.

As I don't believe the receiver bridge does much of anything for slamfire preventions, I believe primer sensitivity is the primary cause for those things, and I only use CCI #34's in my M1a (though I have some older WLR still around). I believe the receiver bridge only has two functions, one to hold the back end of the bolt up and the other to pull the firing pin back during extraction. I don't know if having a worn firing pin tang does anything bad in terms of extraction.
 

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I guess if I didn't clearance the bridge, I would have polished the roughness off of the pin. Repeat as necessary. Some day you will have removed enough material, without going too far, for everything to function properly. Thereby preventing the tail from fatiguing and breaking.

Or do my simple test, and get more agressive grinding the tail. Nothing to lose but a pin you are going to replace anyhow.

The positive retraction afforded by the ramp/tail is only of import when the gun is so dirty the pin could get stuck. An neither of my fixes would interfere with the retraction function.

But YJBMV. (Your Judgement Basis May Vary)
 
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