The Nitrile O rings I bought from Altec have proven perfectly suitable so far. It'd be interesting to see if the silicone ones need less grease for lubrication though. It'd be one job less to worry about when loading up!
Part numbers are:
7mm Nitrile Part No: ORN - BS006 Stock Items in packs of 50
5mm Nitrile Lot No: 134 - 8883 Special Orders in packs of 100 (unless they've decided to stock these too now.
The 7mm rings were very inexpensive lasttime I bought them, far less than the 25pence each being charged elsewhere. I can't remember exactly how much they were now, about 5pence each I think.
As the 5mm ones weren't stock items they were more expensive.
Give these a try, see what you think
Cerwyn
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Hobby collector of mainly WW2 era uniforms, headgear, field equipment and replica weapons.