Mrod .177 cal Barrel O-ring Groove OD?

[FuzzyGrub]

Does anyone know what the OD of the O-ring grove is on the Mrod .177 cal barrel?   The O-ring is 1.5mm X 4MM, so the O-ring OD is 7mm or 0.276".   I suspect it has to be a little less than the O-ring, probably in the 0.260 - 0.270" range.   While I have one, taking in off and not having the right tools to measure, is why I ask.  I appreciate any input.  Thx.

[WHITEFANG]

Not sure of the size. Captain oring has kits available and you can buy just that seal but he has a minimum order. The kits come with all o rings for 2 complete builds. Great vendor.
To unfloat the barrel o ring #018 will indeed work I use 2 of these in the polyurethane on mine and have 1 hole accuracy at 25 yards in .177. Call him if you have to and mention OC in Arkansas sent you.

Some of the seals in the Marauder are metric, at least the .177 breech seal is. I order the rebuild kit and 10 extra breech seal. Low cost and good o rings. I have ordered many PCP or in replacements from Jon.

http://www.captainoring.com/store/p35/Crosman_Benjamin_Marauder_BP1763_%2F_BP1764_%2F_BP2263_%2F_BP2264_Air_Rifle_2x_COLOR_CODED_O-Ring_Kit.html