I was able to drill new production Daisy air tubes to 3/32" using oil and a long drill bit. Totally doable. But as the size increased so did the difficulty I had making a clean hole. I broke a few bits drilling them to 7/64" so I didn't even bother to try 1/8".
The 0.157”/4mm ID custom tubes work great- IF you're using a stronger spring rate. They require a reamed abutment seal because the tubing they're made from has a larger OD (11/64") than the stock tube. But I believe you'd actually lose MV using one in an otherwise stock gun, but that's a guess on my part because I never tried.
Dave, 2 suggestions.
1- I can drill out tubes. Only problem with that is that I don’t have any to drill. Sent them all to Cobalt327. I can drill at 3/32”, 7/64”, #40, and 1/8”. 1/8” is a bit tricky to do without a precision collet lathe to do it accurately enough. Its worth it in my opinion.
2- See if Cobalt will share.
I’m slowly working on putting together a daisy parts order. I will add some and get them drilled.
Or, there is the ultimate custom air tube that I can make. Ask Cobalt his opinion about that.
Dave, Cobalt makes a great point. When going to the larger sizes, a stronger spring is required. At one time I did experiment with bigger holes with standard daisy springs and lost mv till I preloaded them.
My memory isn’t what it once was. Maybe Cobalt can say what the maximum drill size is that would work well with a stock spring. Seems like 7/64” or #40 worked.
Cobalts HP spring really solves a lot of problems. I don’t remember if you have one or not. If not, I urge you to get one.
We also ultimately found that the id and the length of the stock shot tube is limiting. Hence, all the effort in getting to better fitting/ longer tubes. Really comes down to what your goal is and how much money are you willing to spend.
I’m still trying to figure out what the optimum combination is.
I also have not tried my custom air tube with a standard spring rate. It may act differently for 2 reasons.
1- the od fits the id of the shot tube much closer, so you have less air leak back down the tube.
2- the tube is longer so it closes off the bb port quicker, also reducing air loss.
Looks like I’m going to have to do a research project. Try out a custom air tube in an otherwise completely stock RR.
So, I’m sorry if this isn’t a satisfactory answer to your question.
All that said. If you are not in a big hurry, I will be happy to drill tubes when I get some.