How's the dart fit?
I have the same setup as you, but had to put tightening rings in the brass to give a good grip on the dart.
Try that, and see how it goes...
I'm afraid I don't know what those are. Would someone care to explain?
Doesn't matter what darts you use, or what barrel. The fit for a springer should be easy to blow the dart down the barrel, but not so that it falls down on it's own. The drat should make a popping noise as it leaves the barrel. You should also glue some foam on your plunger head or under the cap so the plunger head doesn't shatter. The seal should also be nice, but not too tight. Push in the plunger tube with your hand without a spring, and you should be able to stop it by putting your finger over the barrel, but it should be easy to push the plunger rod in the tube. Also, putting in more springs sometimes ruins the range, for reasons I do not know. Spend the $3 or so and buy a spring from your hardware store.
I use sonic micros, and they DO pop when I pull them out of the barrel. Maybe my 9/16" has a strange ID or something, but my darts only just thin enough so I don't HAVE to twist 'em in.
What lube did you use? I too believe your problem is the dart fit.
Something called Hunting's Silicon Spray Lubricant. It says on the can that it's fine for rubber, PVC and electrical insulation, so it's probably Nerf-safe.
As much as I'd like to start experimenting with 17/32" brass, brass tubing costs way more than its worth, especially since PETG is cheaper (even with international shipping), lighter and (apparently) a better fit. So no further experimentation with barrels till I get my PETG order over to OMC.
Spring replacement is not an option for me. You wouldn't believe how badly hardware stores are stocked over here. The only large chain we have is Ace, and they don't carry ANY remotely suitable compression springs.