Mini-14 ...... firing pin length from bolt face

20 August 2019

I just installed a new Glend Arms firing pin in my Mini-14.

I found a website which said, "The factory will fit one with .020" protrusion, but for absolute reliability, .025" or .030" is superior."

I did some filing-to-length and the maximum measured protrusion on the new pin is now .027". Yesterday I did 100 rounds of test fire, no problems.

Here's some pictures of the dimple in the primer, does this seem excessive ?? I have no experience with "how deep is too deep" and would welcome some insight.






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Looks a little too deep to me, but I'm no expert.

Looks a bit to deep to me as well.
By the way, were did you get the firing pin from?

UPDATE 03 SEP 2019

I bought a Glend Arms firing pin from MidwayUSA.

Based on the above suggestions, I pulled the firing pin and shortened it by 0.003", protrusion from the bolt face is now 0.024". Then reassembled and test fired 120 rounds, no problems.

Here's a sample of primer dents with the shorter firing pin ......


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Hi,

Two questions:

1. Was there something wrong with the factory pin, as in misfires, broken, or otherwise defective?

2. If the factory pin was not defective, how far did it protrude? Those last pix with 0.024" protrusion still look like the pin's hitting plenty hard.

Rick C

27 February 2020

As the OP, I would like to update this thread which I started back in August 2019.

UPDATE: the firing pin broke today !! After only 1,572 rounds fired, the Glend Arms firing pin broke. But not as expected: it was the back end which separated from the main shaft, not the tiny tip. Weird.

This makes 2 Glend Arms firing pins which have broken in my particular Mini-14. I've now learned my lesson and will find a firing pin that will get the job done.

I would like to write a letter to Glend Arms, might anyone have their mailing address ?? Otherwise I'll 'net search for it.

Send it to Ruger and they will likely fit a pin under warranty. Ask for a spare while they are at it and they will probably oblige.

what prefix is your mini... I have lots of new parts from an armorer's kit

Mine is a Ruger Ranch, .223 caliber, serial 197-116xx.

I'm definitely interested getting things working again.

I'm not a smith but I'd say from the pictures it was hitting the primers too hard and eventually caused the pin to fail... the metal would break at its weakest point were ever that is.

Here's a little different spin on these 'long' firing pins.

Ignoring the virtues of shooting boxer-primed ammo as opposed to berdan-primed, some folks choose the later, as the ammo is cheaper. But, some Mini's just will not ignite berdan-primers. It's not because the strike is not forceful enough, but it's because the strike is not deep enough. The little bit extra in length in any given firing pin can allow the use of berdan primers when the nominal factory length firing pin may not.

In this case as I noted above: the tip did not break ...... the back end of the firing pin broke off. Why that is a "weak link" location makes no sense to me, but that's where it broke.

My understanding of the current Glend Arms design is that it is manufactured in two pieces and hard soldered somewhere in that area. Likely a weak point in the design.

I ordered an oversize pin from firingpins.com. Single piece design turned on a CNC lathe according to their description. Will post back with how the fitting goes.

NikA,

There it is: soldered joint. Yep, that would be a weak point.

Sounds like I also need to get me a pin from firingpins.com ...... Thank You for that info !!

And for a personal project, I'm going to goof around with the broken pin and see if I can put it back together.

Won't have time to get the fitting set up today, but can give my initial impressions measurements (approximate, taken with calipers):

Stock pin is cast, has a cruciform cross-section for most of its length with the extractor cutout limited to ~1/2" back from the tip. When fully forward, it is .015" recessed from the back of the bolt and has a protrusion of .037" (Mini-30).

Replacement pin is likely machined from bar stock; I see no rough surfaces. Minimal machine marks, has likely been tumbled. Extractor cutout is nearly the entire straight length of the pin (which I believe matches an older factory design). When fully forward, it is recessed .006" from the back of the bolt and has a protrusion of .069".

Looks like there is plenty of material to work with on the new pin. Probably won't get to the actual fitting and testing for a few weeks.

Just today I received a new firing pin from the FiringPins.com folks.

Tomorrow I'll get started on fitting.

UPDATE 14 MARCH 2020

A few days ago I received the new Mini 14 firing pin from FiringPins.com ..... got it fitted. The tip of the firing pin extends 0.022" from the bolt face.
Test fired at the range, 130 rounds, works fine.

Here's 5 fired brass cases showing the .022" dent in the primer. Up close under magnification each looks more "violent" than unmagnified.
(if you would like to compare: high up in this thread I have a picture of .027" dents, then I did more filing to get .024" dents)

I finally got around to fitting my pin. Ground 0.006" off the rear of the pin for 0.012" recession from the back back of the bolt, then approximately 0.015" off the front of the pin and hand finished with a file and 400 grit sandpaper to a final protrusion of approximately 0.052". Fired 10 steel case rounds, 100% ignition and fired primers as shown in link below (img tag doesn't work for whatever reason).

https://ibb.co/PF16QQB

45blackhawk, I notice a lot of roughness near the firing pin impression on all your fired cases. Did you deburr the firing pin hole on your bolt? I found that there was a pretty significant burr on mine that I cleaned up by hand with a 118 degree countersink bit.

WOW, you are running over double the firing pin protrusion (.052") that I am running (.022"). That's of interest.
--- I see that your Mini is a -30 (7.62x39) ...... whereas mine is a -14 (.223).
--------- Would that make a difference for firing pin protrusion ?? I have no idea.

Your primer dents look nice and smooth.

No, I did not deburr the firing pin hole on the face of the bolt, I never even thought of doing that ...... so now I have a project. Thanks Much for the good idea.
And while I have it apart, I will use some fine-grit sandpaper on the firing pin tip to add some "round & smooth & polish." All I did was use a diamond file to make the tip more round-ish.

Yes, protrusion for a -30 will be much more than a -14. 7.62x39 is loaded with a large rifle primer as opposed to small rifle in .223/5.56, the stock specs for protrusion between the two sizes are different.

I based my target protrusion numbers on specifications for other 7.62x39 firearms.