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Old 10-28-2011, 05:49 PM   #1 (permalink)
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Join Date: Dec 2008
Location: Houston, TX

Rainmaker Restoration Project - w/ hammer face pic

I found an older (?) bag o' rainmaker in the BSTs and wanted to see what you guys were talking about. It was in great condition, other than "some assembly required". I did some homework and found some old threads, this one turned out very helpful...

Rainmaker stock board dwell...

Thanks to MondoMor and Mad Marty for that.

These things are a lot bigger after you put them together.
And yes, on HPA and a ported valve, still loud.

The hammer face picture is on the last post.

I wanted to keep it mostly original, but add some Mad Marty mods and see what I could do with the original design

I bored out the valve to match the body ports, recessing the seat since there was plenty of meat, and made a new valve poppet.

I worked up the Mad Marty carrier mods with a link set screw and center post.

I was studying the sear alignment for what I remember is MM's mod #5 for polishing and fitting the sear for easier lock up. What I came up with instead was to fit a 1/16" roll pin in the back of the hammer which holds the sear in alignment with the carrier when they are not yet latched. I'm surprised these things worked originally. Between the tool marks on the carrier face and the way the sear was bumping the vertical edge of the carrier, it looked like it would just ram the parts together all the time.

This roll pin mod also keeps the sear spring tucked up in the hammer so it doesn't drag the body.

Never mind the 1/16" hole near the front of the hammer. I wasn't a good day in the garage.

I'm trying to show where I ground a little off the sear for the final fit, making sure that the sear has a full latch on the carrier. If I had drilled the roll pin hole higher up in the hammer, it would not have been necessary.

I decided to try some high volume (3/32") promaster tubing on the LPR supply to the solenoid. Partly to add volume and also to try to get away from the tiny elbows that were on there. It may kink enough to be the same, but it seems to work well enough.

I ground the ports in the LPR stem, and added some flow slots in the top. Those are just in case the stem gets pushed up against the tubing fitting, which seemed like it would keep the pressure from kicking the piston closed in good time.

Made a new bolt. Mad Marty definitely has a point on custom bolts. The stock bolt didn't seem to fit the space very well. The largest o-ring diameter on the bolt was around 0.685, while the bore was very consistent at 0.699

Bored out the HPR back to add some volume (for HPA).

I polished and cleaned up the LPR orifice. That is not a shadow in there, it is partial anodizing. The hole had a small burr in it and the seat was uneven, so I cleaned that up. With all the odd mods, it still runs right at 80 psi.

I still need to go through and loctite it all down and will probably stiffen the valve spring since I seem to have a lot of velocity overhead available (I started at about 350 fps).

I think I'm going to work on the feed neck and get a loader matched up to the detent next.


Got my macro line fittings and added a feedneck mod. My tape wasn't thick enough and I made a couple of marks on the body from the lathe chuck, but I got away from the side screw feedneck. There's plenty of meat on the inside of the original feedneck to thread or clamp onto.


A couple of odd notes. The ball detent was bent too deep, not just protruding too far into the breech, but also presenting too steep of an angle to the bolt. My first assumption was that it was intentional, but I'm not so sure. Along the same lines, there were only four pair of spring washers in the HPR, where the original design was five. I bought some extra washers from JT parts as I couldn't find the exact size anywhere else (and the JT price wasn't bad either). Five pairs is not as stiff and should last longer and provide higher flow for the same pressure setting.


A clarification on the bolt link mod and center pin mod:

The link set screw is pretty easy if you go at it right. On the carrier, the link hole goes all the way through. Pick the side that has the sharpest, cleanest hole edge to hold the link. In the opposite side, run in a plug tap (10-32 iirc, it is already the right size for 8 or 10). Run it in far enough to jump the hole in the center, but leave the other side of the hole intact for the link. Use a set screw long enough to jump the hole, with a little blue loctite, to support the tip of the bolt link in the carrier to keep it from pushing down into the carrier. This keeps the bolt link aligned and prevents it from digging on the body and slowing things down. One set screw installed, basically.

The "carrier pin mod" is a little more involved, you need to come up with a steel "post". First part is to heat up the carrier and remove (unscrew) the hollow center pin. You drill and tap through the hammer face to accept the center pin. Hitting the centerline of the hammer face is important. After you screw it in, a thread or two will be sticking out of the face. File, grind, or turn this flat. You now have a relatively hard face to strike the valve.

The second part is scrounge or make a solid steel post with short threads that are the same as the center pin you just moved. The length is about an inch, but is determined by the fact that it fits inside of the center pin that is now on the hammer. I think I've read where a long shank bolt can be cut to fit. The better the fit, the less slop you have in the carrier/hammer match up, but not too close to trap air, oil and grit. I made mine on a mini-lathe. You could probably build one up with some stainless tubing over a bolt (hmm..). Make sure your new post doesn't interfere with your bolt-link-mod set-screw when you screw it in, then install it with some blue loctite. With some sort of sear mod, you should be able to just shove the carrier and hammer together easily, but be careful if you use the spring and play with the sear. When you put them together, you should be able to slide them around the body without binding. Again, be careful of the sear release pin mounted in the body as it can release the sear and fling things around.

If you haven't noticed imho, rainmaker = loctite.
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some things are stickier than others

Last edited by Spider!; 07-12-2017 at 05:05 PM. Reason: mod clarifications
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