Large firing pin vs small firing pin

[vivdav]

I hope this is not a dumb or redundant question but changing to Lapua brass in 6.5 creedmoor and wanted to make sure I have an AI AT with a small firing pin. I shot factory Berger this weekend without difficulty. The serial number on the bolt is 21,xxx. I looked at Mile High website and could not quite figure it out. Thanks

 

[redneckbmxer24]

Measure you’re firing pin...

 

[Supersubes]

Small firing pin is about 60 thousandths, large is 80 thousandths.