Hi guys, Sorry for bumping an old thread, but I am having almost the same type of problem. I have done plenty of searching and research to no avail.
I have an old 007 I put all my Phantom internals into. initially velocity was low and gas consumption was high. I tried springing, no better. I read some great stuff on Power tubes in the Redux section, so I set out to turn out a copy of Bacci's modified Ranger power tube.
Dropped that in and the velocity came up to 230fps, but no matter what spring combo, it maxed at 230. Figuring there was some other restriction in line, I went back to the shop with the TPC in hand and turned the OD where it sits in the bolt to increase the flow through the bolt. That brought it to 250 from the third to the sixth shot, where it started dropping off fairly rapidly. by shot 15, it was back to 220fps. That was with a very stiff hammer spring. The paint to barrel match isn't perfect, but it won't roll out.
I have been using random springs I have had sitting around for years, so I don't have any color combos to throw out. Anyone know where I can get a spring kit with valve springs? Any ideas why this thing won't get up there in velocity?