I have a small stash of spare parts for my M4 which includes the gas plug o-rings and firing pin retaining pin o-ring.
The o-rings are a standard size, so rather than ordering them from Stoeger or Brownells, you can get them at any auto parts supplier for a fraction of the cost. I bought mine at Fastenal. Get the standard Nitrile o-ring (the black ones), no need for the brown Fluoroelastomer or metal detectable nitrile versions. I think they might also sell them at Princess Auto in their o-ring box sets , but I cannot vouch for the quality.
Info as follows:
Firing pin retaining pin o-ring: Benelli part number 60297, use Dynaflo AS568-007, ID 5/32 OD 9/32 W 1/16, commonly known as a #007 size o-ring.
Gas plug o-ring (two required): Benelli part number 70107, use Dynaflo AS568-011, ID 5/16 OD 7/16 W 1/16, commonly known as a #011 size o-ring.
The o-rings are a standard size, so rather than ordering them from Stoeger or Brownells, you can get them at any auto parts supplier for a fraction of the cost. I bought mine at Fastenal. Get the standard Nitrile o-ring (the black ones), no need for the brown Fluoroelastomer or metal detectable nitrile versions. I think they might also sell them at Princess Auto in their o-ring box sets , but I cannot vouch for the quality.
Info as follows:
Firing pin retaining pin o-ring: Benelli part number 60297, use Dynaflo AS568-007, ID 5/32 OD 9/32 W 1/16, commonly known as a #007 size o-ring.
Gas plug o-ring (two required): Benelli part number 70107, use Dynaflo AS568-011, ID 5/16 OD 7/16 W 1/16, commonly known as a #011 size o-ring.
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