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1/25/2018 7:38:29 AM
Posted: 9/6/2010 10:39:53 AM EST
[Last Edit: 9/14/2010 2:42:31 PM EST by SwissSteel]
Anyone know the o-ring size for the Comp M4 battery compartment? Source for spares?

I checked my favorite sources, but didn't find anyone who carries o-rings for the Aimpoint.

I'm guessing it's metric, maybe 16mm x 19mm x 1.5mm. I tried 5/8 x 3/4 x 1/16 - id seemed to work ok, but couldn't screw the cap over it.
Link Posted: 9/6/2010 2:52:40 PM EST
try lubing it with a little grease... Rubber can become dry over time.. O-rings like grease....
Link Posted: 9/6/2010 3:23:52 PM EST
Actually the best lubicant for O-rings is silcone grease, it won't dissolve the rubber and it is completely inert.
Link Posted: 9/6/2010 4:00:25 PM EST
good tip...
Link Posted: 9/6/2010 5:51:12 PM EST
Originally Posted By jlow:
Actually the best lubicant for O-rings is silcone grease, it won't dissolve the rubber and it is completely inert.

Good advice, buy special O ring lubrication. Some O rings do not like petroleum based products.


Link Posted: 9/7/2010 12:25:58 PM EST
Thanks for the ideas

I tried with a little grease, but still was unable to screw it down completely. The original o-ring appears to be a little thinner (smaller O.D.) than the replacement I picked up.

Sent an email to Aimpoint, hopefully they will respond. Doing a search only turned up the NSN # 5331-01-549-5836 - but no dimensions or source.

I'm surprised these aren't readily available.

Link Posted: 9/7/2010 3:11:30 PM EST
[Last Edit: 9/7/2010 3:11:56 PM EST by jlow]
Glad to be of help. If you are still having problems with the O-ring, take the optic off and bring it into a hardware store to get an on location fit. if you are still unsuccessful, go to a more specialized place like Grangers and you can be pretty sure to find one.
Link Posted: 9/14/2010 3:02:40 PM EST
1st - I am disappointed with Aimpoint, no reply to my email asking for o-ring size or sourcing information.

Took a shot at it being metric and ordered online (16mm id x 19mm od x 1.5mm cross section).

Came today - appears to fit correctly.

I also used Silicone grease as recommended above. Makes it much easier to screw the cap on.

Picked up a small container in the local hardware store near the faucet repair parts.
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