No Go Gauge for Firing Pin Hole for AR15 Bolt?

[Religious Shooter]

I was having problems with my AR.  Was told to look at the FP hole to see if it was too large.  It looked larger than the new spare bolt I had.  Swapped out the bolts and the rifle began to work properly again.  Used same FP and carrier.

 

Anyways... is there a no go mic/pin or whatever that I can use to check if the bolt's FP hole is to large?  Any other way to check other than firing and seeing if it malfunctions to see if the firing pin hole is too large?

 

Are there any oversized AR15 firing pins being sold?  I want to see if I can continue using this expensive bolt until it breaks a lug.

 

Thanks.

[dauntedfuture]

What issues are you having? I highly doubt that the firing pin hole cause them; if the firing pin hole was too big you could get primer flow issues but it's highly unlikely. 

 

Was as the first bolt perhaps from a "bargain-bin" supplier or gun show special?   You do pay for quality, out spec parts are less likely at some of the "better" companies.  Many outfits are simply rebranding someone else's stuff so it can be hard to tell.  

 

If the rifle now runs with the "new" bolt you have fixed your problem.  

 

Some firing pin holes have a little more radius then others.  

[Religious Shooter]

Well in case someone has the same problem...

 

http://www.zediker.com/books/ar15/images/AR1522.pdf

 

I check for firing pin hole size, though, to make sure it is, ideally, toward the small end of the blueprint tolerance, and never over that amount (0.058-0.060). A bolt with an oversized firing pin hole might tend to produce pierced primers at lower cartridge pressure levels, so check it out if you’re having chronic episodes. A larger pin hole encircles more primer surface, and can then act more easily like a cookie cutter around the firing pin. Specs call for 0.029 protrusion, so consider that also if you’re having a perforation session.

 

1/16" drill is supposed to be .0625".  I measured a drill that I had on the shank and it says it is .060.  So if you need to check your FP hole... try a 1/16" drill using the shank.  If it fits... that bolt is a no bueno. 

 

The 1/16" drill fit in with plenty of room.  I have roll pins that measure around .063 and those fit in the problem bolt as well.  

 

Problem I had was light strikes and stuck case on the bolt face while shooting a match.  It was during a match so I couldn't exactly pick up and examine every case fired.  Shooting factory PMC ammo (not known to be hot) and some Israeli Independence ammo (known to be very hot).  

 

When I took it out to clean I had "cookies".  Basically what Zediker was saying above.  Little round disks from primers.  

 

The cookies also locked up the safety and the trigger group.  Couldn't fire the gun or put it in safe (to ditch it).  After shaking it I guess it shook loose and started working again.

Edited March 28, 2017 by Religious Shooter

[dauntedfuture]

It could have helped if you included what the problem was first.  Yes, if your having pierced primers, blow primers, or primer flow etc issues then yes Firing pin hole could be an issue.  

 

An oversized firing pin will not help with this particular issue.  

 

This is is also why ppc and some other caliber rifles have "small firing pins".  You are able to run a little hotter with less of a chance of pierced primers.  

[Religious Shooter]

Huh?   I was asking if there was a gauge to measure the FP hole.  I wasn't asking for help diagnosing the problem.

[Steve RA]

Find the specs for Govt. AR and get a drill bit of that size to use for a gauge.