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+--- Thread: Firing pin measurment (/showthread.php?tid=16867)
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Firing pin measurment - VASCAR2 - 09-03-2018
The milspec length for a AR-15 firing pin is 3.280 plus or minus .001. Probably need to shorten a firing pin to 3.27 with a 2.80 length 6.5 Grendel bolt. I think it still best to measure the bolt, firing pin and protrusion before shortening a firing pin. I’d probably use a file to shorten a firing pin.
Firing pin measurment - grayfox - 09-03-2018
Toolcraft.com is their website I think...
maybe give them a call.
Toolcraft, Inc.
1877 Rutherford Road
Marion, NC 28752
Phone: (828) 659-7379
Fax: (828) 659-7329
Firing pin measurment - TraderRik - 09-04-2018
Thank you both!
Firing pin measurment - c3k - 10-18-2018
I think someone mentioned shortening the firing pin at the primer end? I'd think (as a total newb), it'd be best to leave the tip nicely radiused and to file down the back of the pin where the hammer strikes it. Just my .02.
Firing pin measurment - Lastrites - 10-18-2018
c3k Wrote:I think someone mentioned shortening the firing pin at the primer end? I'd think (as a total newb), it'd be best to leave the tip nicely radiused and to file down the back of the pin where the hammer strikes it. Just my .02.
Unfortunately reducing the back of pin will do nothing for shortening the tip protrusion, easy enough to find a stainless steel FP and circumcise the tip a bit for the reduction. Go slow and measure often or compare to one that is of the shorter length if you currently have one.
Firing pin measurment - VASCAR2 - 10-21-2018
I bought a PSA 12” Nitride 6.5 Grendel pistol kit. Got it together Friday and shot it Friday and Saturday. Functions 100% and firing pin indentations look spot on. I decided to measure the bolts and firing pins of various firearms to see how much difference there is.
PSA 12” Nitride barrel, Nitride 6.5 Grendel BCG
Bolt length 2.808
Firing Pin length 3.275
Faxon 18” build PSA Nitride BCG Monster GB bolt
Bolt length 2.812
Firing Pin length 3.2765
Faxon 16” Build Precision Firearms Nitride BCG
Bolt length. 2.8095
Firing Pin length. 3.277
Shilen 20” build Shilen supplied bolt PSA Phosphate Prem. BCG
Bolt length 2.814
Firing Pin length 3.275
J&T Distributing upper (AA bolt) 6.5 Grendel upper
Bolt length 2.814
Firing Pin length 3.274
I also measured my 5.56/223 AR-15 bolts and firing pins
PSA 16” SS midlength Freedom
Bolt length 2.798
Firing Pin length 3.2755
RRA Build RRA BCG
Bolt length 2.7965
Firing Pin 3.279
Colt 20” Competition H-Bar
Bolt length 2.799
Firing Pin length 3.280
After looking at these different measurements I think in a mass produced industry an employee assembles a bolt carrier group from bins of parts. I suspect a gauge is used to verify the firing pin protrusion is between .028 and .036. If the firing pin protrusion is out of spec they might try a different firing pin bolt combination. If the parts fail they go in a reject bin. There is a .008 variation to account for different length firing pins or bolts. Tolerance stack and you can get excessive or inadequate firing pin protrusion.
Firing pin measurment - VASCAR2 - 10-21-2018
Here is a composite list which makes comparisons easier.
Firing pin lengths
3.275
3.2765
3.277
3.275
3.274
3.2755
3.279
3.280
Shortest 3.274
Longest 3.280
All within .008
Bolts 6.5 Grendel
2.808
2.812
2.8095
2.814
2.814
Bolts 5.56/223
2.798
2.7965
2.799