Disassemble your hammer catridge. On 03s you need a spanner wrench, 04s have a hex cap on the hammer cartridge, which is much easier and requires one less tool.
Remove the hammer internals carefully. I did mine over carpet or a towel or something. If the hammer is stuck in there, you can tap it out into your palm. It will look like this when you get it out. Then clean the inside of your cartridge w/ qtips.
Now for the hard part, remove the hammer weight from the hammer shaft. From my understanding, they are red loctited from the factory. Whatever you do, don’t score up the shaft or brass fitting on the tail in of the shaft. You will want to store away your stock hammer incase it is ever needed in the future, or if you sell your gun, and the new owner wants it. Then remove all the orings/bumpers/stops from the stock hammer. It will look like this. Robtown hammer is above the internals, stock is on bottom. Parts are in order from left to right on how they should be put on your hammer.
You will now need to put the internals on in reverse order on the new hammer. I put the small bumper on the shaft first. Then put the tophat stop on (this stops the forward stroke of the hammer w/in the cartridge). Put the tophat stop on concave side down so that the bumper seats inside of it. Now put the UR70 010 oring on the tail of the hammer. Apply a bit of AKA lube to the tail oring. Then put the other UR70 010 oring in the countersunk side of the cartridge cap and put a bit of AKA lube on it as well. Then slide it over the hammer shaft. Apply a small drop of blue / removable loctite to the threads on the cap threads. Then tighten the cap onto the cartridge, but don’t overtighten. Then slide the large bumper onto the hammer shaft (in between the hammer weight and the cartridge cap, this stops the backward stroke of the hammer). Then put a drop of blue loctite on the threads where the hammer weight threads onto the hammer shaft. I didn’t take a picture of the robtown one after I finished, but here is the stock one. This cap should be screwed into place though.
Install the robtown valve using a drop of AKA lube on the outer orings of the valve body. Make sure when you put the valve in that you line the hole on the valve body up w/ the hole in your gun where the valve setscrew goes. Notice the valve hole is facing same direction as the setscrew hole.
Put a drop of blue loctite on the valve setscrew and secure the valve in place with it. Then replace your valve spring and front cap. Then replace the hammer cartridge and bolt, and then air it up……..NO LEAKS right. Well, I didn’t have any. If you do it right, you won't have any either.
Now all you have to do is fine tune your LPR, dwell, and HPR to get a consistent, safe velocity.
My settings are:
Dwell = 9ms
HPR = ?
LPR = 69-70 psi
Chronograph = 275-280 fps
Every gun is different, but these settings work well for me. BE SAFE AND HAVE FUN....Thats what its all about!