Tuning FX Dream Tac Compact low on power

Max out your preload screw, set hammerspring wheel to max, set transfer port wheel to high(or .25/.30). Shoot a couple shots over a chronograph. Slowly(1/8 turn at a time) raise the regulator pressure, then shoot over chrono again. Fps should rise. When the fps numbers start to drop, go back 1/8 turn. This will be your max.

If fps drops immediately, your reg may already set too high. Back it down(1/8 turn at a time, dry firing a couple of times to let the reg settle) to a lower pressure and repeat steps above.

Well, I wouldn't want to go any higher on the reg pressure as FX states that you can void your warranty if you exceed 160 bar, which is where you already are.

Funny thing is that both UA and Pyramyd talk about muzzle velocities of 800-820 fps in .25 cal DL Compacts. So the gun should not only shoot Kings at 750, but maybe more.

Does it have the OEM barrel on it (480 mm)?

I would just try going down on the reg pressure, to see if a reg pressure that high (160) is too much for the hammer (weight & spring) to overcome to open the valve fully/quickly/efficiently.

No, not too much.

Barrel length to me is a bit of a mystery. The FX site says that the .25 cal Compact has a 500 mm barrel (or 500 mm 'barrel' length including the shroud?). UA site says the .25 has a 480mm barrel, and PA differs again, saying that the .177/.22 have 320mm barrels and the length only jumps to 380mm in the .25.

All I was wondering in my post above is whether the original owner somehow put on a shorter .25 cal barrel to keep the gun as compact as possible, and that was why it was apparently only putting out 750 fps for him.

160 reg is probably too high for the HS, but the gauge could be off so... You might want to ask whoever you got the gun from?

I usually start the process I described above at about 130bar or so. As soon as you start moving the reg, the fps drop/rise should tell you which way you need to go. Getting a .25 King over 800 fps shouldn't be a problem, even with the 380mm barrel.

Good luck

If you have too much reg pressure and too little hammer spring, you will get diminishing returns with higher reg pressures as the valve with more pressure against it requires a heavier hammer strike (considering your hammer spring is maxed out). De-gas the gun and turn your reg all the way in until you feel a little resistance. Then back it out a 1/4 turn. Air it back up, adjust your your reg back up at about 120bar. shoot between further reg increases (about 5bar per adjustment) over the chrony until you start to lose fps again. And turn it back down to the highest fps you could achieve. Then shoot for groups using the micro hammer adjuster to get your barrel harmony right. They recommend about 140-150bar max on the reg for the Dreamline compacts. Hope this helps. 

I'm curious how this turns out. I'm new to the FX world with my .22 Dreamline Tac Compact, and also almost 10 years since I was last tinkering with airguns, so I've got a lot to remember and learn. Out of the box, mine shot JSB 18s at less than 600fps. I've tried a variety of settings, including the reg at ~125 up to 150, but can't get more than 825fps. Yet I read others with (apparently) the same rifle getting 880 with these pellets. I haven't much time lately to test again, but I figure I need to go back to square one.

FWIW, I bought mine new a few weeks ago, and it came with a 300mm barrel (measured it myself, as I also have read conflicting numbers), 300cc CF tank, and the plenum.

I have a Compact in .22. Wasting air chasing power with a short barrel causes weird things to happen. Even if you manage to get your dream velocity out of a short barrel you may still notice weird velocity spikes across a full shot string. The bottom line is you’re just pushing the platform too far. FX clearly stated when they introduced the gun that it is not a powerhouse. Some guys just refuse to believe it. My .22 came with a 380mm barrel. After trying all kinds of magical trinkets like plenums, probes and transfer ports, I finally just slapped a 500mm barrel on it and the gun hit 880fps in its sleep. So I shortened the 500mm barrel system down to around 430mm to keep the gun compact and still easily achieve my target velocity of 880fps and have my wheel on #4. Those two clicks below max have the gun setting right on the knee of my 147b reg setting. 

Oh, get rid of at least one of those plenums. Whoever did that obviously did not understand the relationship between plenum volume and barrel length. If you don’t have enough barrel length, plenums don’t do jack.

my tac-compact bottle gun with 1 plenum ext, ernest's dual TP, set on 25/30

reg on 150, jsb 18.1gr = 888fps continuously accurate at 35yrds.

HS not on max, side lever effort is minimum, very smooth !

I don't want to highjack this thread, but one more question: Gendoc - how many shots do you get (and what size is your bottle or tube)?

about a mag and a few...maybe 25 or so....its a 300cc bottle

As a comparison I get over 40 shots with 18.1’s going 880fps with a 300cc bottle. It’s amazing what a couple inches of barrel can do. Just not wasting any air.

Just reading back through this thread. A lot of good suggestions, but it can really be tough to identify particular problems "over the phone" so to speak. Plus this gun has be modified/"worked on", so it can be tough to tell exactly what is going on with it now. 

You mentioned that the highest fps come when the Transfer Port is set to medium. All things being the same, this CAN indicate that the TP hole in the barrel is smaller than the hole in the receiver's TP. That would be the easiest fix- try a barrel with a bigger(oval or bridged) port. OR it could be you don't have enough air pressure in the plenum(because someone has made it too big a volume to work properly). Essentially, the smaller medium size hole is the largest diameter to make use of the air in the plenum. Either of these will not allow the gun/barrel to make use of the less restricted( bigger hole size) air coming through a larger TP setting hole.

All things being equal, the 600mm barrel SHOULD yield at least 100fps more velocity over the 380mm barrel. 

Good luck

Based on your last pic, it looks like you're shooting 26.4gr Hades. What velocities are you trying to achieve? My stock Dream-Tac compact in .25 shoots the Hades at a consistent 833 fps. Which port are you using on the barrel? Have you checked the barrel o-ring? I don't think those power plenums are doing anything for you, see what you get after you take them off.

Your first mistake was .30 cal and 44gr. You are now getting so far away from what the gun came set up to shoot. Now your Hammer spring might be wrong and your hammer weight definitely is. You went the right direction chasing speed with a longer barrel. But the wrong direction in hoping to send heavy lead fast out of that platform. Because 600mm can send lead fairly fast but the gun has to be built around that caliber.