redbone wrote:Just an F.Y.I. here. I made the inlet hole cut too large and noticed that I was not getting decent pressure or tension in hand when pulling shot.
Also, too large a port weakens the tube when tightening back on the group. Easy fix, just replaced copper tube (in transit).
Will try 2-3mm port vs 5mm next go around.
If tightening back on the group is "weakening" the tube then I suspect one of two things:
You've cut too much off of the tube. You only need a hole slightly smaller than the diameter of the tube inside diameter. That should leave plenty of hip around the cut for strength.
You haven't cut the plug outside dimension down enough. It should be snug, but not too tight.
If you are using the OEM plug for the millenium machines in there then a stepped drill bit run from both sides, hand turn only, should give you a very good fit. 1mm smaller than the OD of the tube would be fine I guess, but I wouldn't try to force a soft metal tube through anything smaller. I cut my hole tight enough that I threaded the dipper tube through and pushed it through at the end. That should be airtight enough.
The first time you put the plug & tube in place make sure the plug comes flush against the back of the group opening so you'll have a good seal. It doesn't have to be perfect, but we don't want water dribbling out of the back of the group. You could test it over a bowl of water - cold water, and see what happens.
I've only done one of these, so there are more here with additional experience that could be relevant in your case.