As we now know, the main bulkhead o-ring the Seac Hunter (and perhaps the Asso too) uses a non-standard 32x2.15mm (ID x W) ring.
I would however really like to find an off-the-shelf ring that could do the job and though I know others have not had much luck, I have not killed off the idea entirely. Yet;-)
I ordered a bunch of o-rings off the web here in China in my efforts to make my own complete replacement sets and of all the o-rings in the Seac Hunter, only the main bulkhead ones seem to not be standard.
I just tried with some different o-rings from the 2mm series and I now have a bit of hope that a 34x2mm (ID x W) o-ring might actually work.
The original, custom ring is thicker at 2.15mm but with an ID of 32mm it is stretched in the groove - which on my handle is app. 34.4-34.55mm (a tiny bit oval). The mass produced 34x2mm ring, while being thinner, is not stretched and thus, the best candidate for an off-the-shelve alternative. Actually, it seems to be
possible to buy 34.5x2mm, so that could be worth a try too, but I couldn't find them in China.
I tried with a 32x2mm (ID x W) too, but the stretching of that made it too thin. So, no less than 34mm ID, I would say.
During my first rough tests (just inserting handle in outer tube) the 34x2mm ring feels like it does indeed compact quite a bit against the outer tube and could hopefully obtain a seal. I only have a handle and the 38mm ID outer tube so it is all by feel.
Around New Years, I'll get to test it properly pressurized when reunited with my guns.
So, even though I am a bit of a tease now, I wanted to chronicle my hopes that some handles might actually work standard 2mm series rings.
But there are a number of factors which decide if this will work with your handle and you have to get a little lucky too:
- One of the main things is the diameter of the o-ring grove in the handle. If it is too deep (too small diameter) the o-ring wont be compressed enough against the outer tube. It seems just about doable if it is around 34.6-34.5mm (higher is better). Here, I am assuming an outer barrel with a spot on 38.0 ID
- The gap between the handle and the inside of the outer tube. If this gap is too big, the slightly thinner o-ring might be pushed into the gap and break. For the same reason, don't use the soft silicone rings. Try to get the hardest rings you can and if the gap is slight it is definitely an advantage. The OD of my handle is 37.5-37.65 (it varies as does the groove diameter)
Stay tuned, I'll take the Seac Hunter apart at the end of the month and try with these o-rings. And I might try them in a Mirage as well, if I have the time