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Atomics are based on the SP Mk 20-25 design, as far as I can see. I've rebuilt both types and there's not a lot of difference between them except for sizes. You don't think they'd make interchangeable parts, do you????? But I digress...
An Atomic first stage with the environmental kit should let no water inside the ambient chamber. Ergo, the first stage should not freeze. Key word here = "should not". I think there's more chance of water getting past that rubber ring than there is getting past the seal on a diaphragm first stage.
Both are good regs. Were I to dive in cold water, though, I'd insist on a sealed diaphragm reg. NO water gets in there, and it is nowhere near as messy as a sealed Atomic to rebuild. Nothing like an ounce or two of used Christolube to clean out of the piston spring!!
Hi lowridersvt,
Do you have a part number for this heat sink you mentioned or know a place I could get it online?
Thanks