NNN
Members
- Nov 12, 2022
- 9
- 12
What started as a simple “I want nicer grips” job quickly turned into a full-on rabbit hole involving Headlight Tint, refillable gas cartridges, bent pot metal, custom screws, and a lot of mental planning and simulation.
The goal was simple enough:
Make the snub nose Umarex M29 look less like a CO₂ replica with cheap plastic oversized grips, and more like a proper compact round-butt Smith & Wesson revolver.
The factory gun looks good, but I wanted smaller round-butt wood grips, but that meant the entire lower CO₂ tightening system had to go.
This is where the sensible people leave the room.
The stock Umarex M29 3"
The main problems were:
My original photoshop concept showing the intended round-butt profile
Paint would have been the easy answer, but it also would have been the wrong answer for what I wanted. I didn’t want to lose the cold metallic feel, durability, or the hard plated look. I wanted the finish to behave more like real blued steel: dark, glossy, metallic, and deep.
The Umarex finish is not normal paint. It’s conductive, hard, cold to the touch, and behaves like a plated metallic surface. At first I assumed it was some kind of dark chrome or black chrome plating, but it may also be black nickel, darkened nickel, or some kind of nickel/chrome decorative plating stack over the zinc alloy.
The annoying conclusion was: I probably can’t truly “blue” the intact factory finish. Cold blue and Aluminum Black can darken exposed marks and engravings, but they don’t seem to chemically deepen the untouched plating.
I tested Hi-Cote headlight tint spray over the dark chrome and the result was annoyingly good. It created the exact “wet depth” effect I was chasing, but with a slightly brownish hue instead of the subtle blue-black tone I really want. It also isn’t durable enough on its own.
The current thinking is a very thin 2K clear/tint mix, possibly with a tiny amount of blue transparent tint, to create a hard dry version of that fingerprint/oil effect.
The goal is a transparent optical filter over the metal, like a barely-there candy coat, just enough to make the existing plated finish look more like deep polished bluing.
The grips came from Thailand and were listed simply as “hardwood.” At first I thought they might be rubberwood because of the origin and the slightly farm/resin aroma.
However when I cut into them the sawdust was almost red which rules out rubberwood. They’re more likely acacia, padauk-type wood, or another Southeast Asian hardwood. The colour was naturally orange-red, and the textured areas were stained darker.
The shape was good, but the factory finish was too orange and a bit too shiny for the look I wanted. I couldn’t just sand them back because the textured low spots would stay dark while the raised areas went pale and patchy. That would have ruined the grips.
After some testing, acetone turned out to be the answer. It stripped the clear coat without needing to sand the texture flat. Once the old finish was removed, I re-stained the grips darker and sealed them again.
To fit the round-butt grips, the rear of the grip frame had to be modified heavily. The marked section of the original frame (shown below) was cut away so that the rearstrap could be reshaped.
The key part was the thin rear strip. The casting already had a narrow section that could become the new curved rear strap if it was carefully relieved.
My logic was simple: If you make something thin enough it will bend, even glass.
That sounds like something said moments before disaster, but in this case it worked.
I cut away the side connection, thinned the rear strap from the inside, then warmed it slightly before bending. Nothing extreme — just enough heat to make the metal a little less brittle, not enough to melt or distort anything.
Then I carefully bent it into the round-butt curve. Because it was now a thin warmed strip rather than a rigid casting, it flexed instead of immediately snapping.
This is pot metal/zinc alloy, so I was expecting a crack, a ping, or some kind of small emotional event. Instead, with the metal relieved, thinned, and gently warmed, it bent smoothly enough to keep going and get the perfect shape using the grips as a guide.
Marked-up image showing the section to be removed and the rear strap to be bent
Frame after bending and cutting lower section, wood grip and 8g c02 cart offered up. The green and red markings are explained in the next section.
The first idea was to use a shorter refillable cartridge and create a steel support frame that locked into the remaining grip structure.
Then the project simplified itself.
The refillable cartridge I bought can be filled from the bottom. That means it doesn’t need to be removed every time. It can stay inside the gun permanently, like a built-in reservoir.
Instead of designing a whole removable cartridge system, I only needed to hold the cartridge upward against the original seal.
The magic observation was this: I could seal it by pushing it firmly with my thumb.
So I didn’t need a complicated steel frame insert. I just needed controlled preload.
The nut follows the shape of the cartridge base, so it can’t wander left or right. Tightening the diagonal bolt pulls the nut upwards and slightly outward, but the sidewall prevents outward movement. So the only useful movement left is upward, which forces the cartridge into the seal.
It’s adjustable, compact, removable and hidden under the grip.
Even better, because the cartridge fills from the bottom, I never have to remove it. The seal stays compressed, the alignment stays fixed, and the wood grips don’t have to keep coming on and off.
For now I tested it with black gas because that’s what I had available. Surprisingly, it works well on black gas too. CO₂ should still be the proper final gas for the system, but the fact it works on black gas proves the mechanical concept.
Internal shot showing refillable cartridge and diagonal bolt/nut system installed
The goal was simple enough:
Make the snub nose Umarex M29 look less like a CO₂ replica with cheap plastic oversized grips, and more like a proper compact round-butt Smith & Wesson revolver.
The factory gun looks good, but I wanted smaller round-butt wood grips, but that meant the entire lower CO₂ tightening system had to go.
This is where the sensible people leave the room.
The stock Umarex M29 3"
The Starting Idea
The factory Umarex M29 has an oversized square frame but I wanted to fit smaller round-butt style wood grips, which means the lower part of the frame has to be reshaped.The main problems were:
- The original 12 g CO₂ capsule sits too low.
- The factory tightening nut would stick out through the new grip profile.
- The rearstrap is too straight for the round-butt grip shape.
- The finish is too light/chrome compared with real blued steel.
- The frame screws are Phillips, which ruins the classic revolver look.
- Use a shorter 8g cartridge.
- Reshape the rear strap into a round-butt profile and cut off lower section.
- Create a new internal preload system to seal the cartridge.
- Hide everything under proper wood grips.
- Convert the Phillips screws into slotted screws.
- Eventually darken the finish to better imitate deep blued steel.
My original photoshop concept showing the intended round-butt profile
The Finish Rabbit Hole: Can This Finish Be Blued?
One of the bigger rabbit holes in this project was the factory Umarex finish. The reason I cared so much wasn’t just curiosity — I wanted to know whether I could somehow chemically blue or darken the original metal finish instead of painting over it.Paint would have been the easy answer, but it also would have been the wrong answer for what I wanted. I didn’t want to lose the cold metallic feel, durability, or the hard plated look. I wanted the finish to behave more like real blued steel: dark, glossy, metallic, and deep.
The Umarex finish is not normal paint. It’s conductive, hard, cold to the touch, and behaves like a plated metallic surface. At first I assumed it was some kind of dark chrome or black chrome plating, but it may also be black nickel, darkened nickel, or some kind of nickel/chrome decorative plating stack over the zinc alloy.
The annoying conclusion was: I probably can’t truly “blue” the intact factory finish. Cold blue and Aluminum Black can darken exposed marks and engravings, but they don’t seem to chemically deepen the untouched plating.
I tested Hi-Cote headlight tint spray over the dark chrome and the result was annoyingly good. It created the exact “wet depth” effect I was chasing, but with a slightly brownish hue instead of the subtle blue-black tone I really want. It also isn’t durable enough on its own.
The current thinking is a very thin 2K clear/tint mix, possibly with a tiny amount of blue transparent tint, to create a hard dry version of that fingerprint/oil effect.
The goal is a transparent optical filter over the metal, like a barely-there candy coat, just enough to make the existing plated finish look more like deep polished bluing.
The Grips: Thailand Hardwood Mystery
The grips came from Thailand and were listed simply as “hardwood.” At first I thought they might be rubberwood because of the origin and the slightly farm/resin aroma.
However when I cut into them the sawdust was almost red which rules out rubberwood. They’re more likely acacia, padauk-type wood, or another Southeast Asian hardwood. The colour was naturally orange-red, and the textured areas were stained darker.
The shape was good, but the factory finish was too orange and a bit too shiny for the look I wanted. I couldn’t just sand them back because the textured low spots would stay dark while the raised areas went pale and patchy. That would have ruined the grips.
After some testing, acetone turned out to be the answer. It stripped the clear coat without needing to sand the texture flat. Once the old finish was removed, I re-stained the grips darker and sealed them again.
Cutting the Frame: The Point of No Return
To fit the round-butt grips, the rear of the grip frame had to be modified heavily. The marked section of the original frame (shown below) was cut away so that the rearstrap could be reshaped.
The key part was the thin rear strip. The casting already had a narrow section that could become the new curved rear strap if it was carefully relieved.
My logic was simple: If you make something thin enough it will bend, even glass.
That sounds like something said moments before disaster, but in this case it worked.
I cut away the side connection, thinned the rear strap from the inside, then warmed it slightly before bending. Nothing extreme — just enough heat to make the metal a little less brittle, not enough to melt or distort anything.
Then I carefully bent it into the round-butt curve. Because it was now a thin warmed strip rather than a rigid casting, it flexed instead of immediately snapping.
This is pot metal/zinc alloy, so I was expecting a crack, a ping, or some kind of small emotional event. Instead, with the metal relieved, thinned, and gently warmed, it bent smoothly enough to keep going and get the perfect shape using the grips as a guide.
Marked-up image showing the section to be removed and the rear strap to be bent
Frame after bending and cutting lower section, wood grip and 8g c02 cart offered up. The green and red markings are explained in the next section.
The Gas System: From 12 g CO₂ to an 8g Hidden Refillable Cartridge
Originally I thought I would need a whole steel subframe to replace the factory CO₂ tightening system. The lower grip frame had been cut down, so the original tightening nut system was gone.The first idea was to use a shorter refillable cartridge and create a steel support frame that locked into the remaining grip structure.
Then the project simplified itself.
The refillable cartridge I bought can be filled from the bottom. That means it doesn’t need to be removed every time. It can stay inside the gun permanently, like a built-in reservoir.
Instead of designing a whole removable cartridge system, I only needed to hold the cartridge upward against the original seal.
The magic observation was this: I could seal it by pushing it firmly with my thumb.
So I didn’t need a complicated steel frame insert. I just needed controlled preload.
The Diagonal Bolt Solution
I shaped a nut to sit against and match the bottom of the refillable cartridge. Then I used a diagonal bolt to pull the nut upward, which pushes the cartridge into the seal.The nut follows the shape of the cartridge base, so it can’t wander left or right. Tightening the diagonal bolt pulls the nut upwards and slightly outward, but the sidewall prevents outward movement. So the only useful movement left is upward, which forces the cartridge into the seal.
It’s adjustable, compact, removable and hidden under the grip.
Even better, because the cartridge fills from the bottom, I never have to remove it. The seal stays compressed, the alignment stays fixed, and the wood grips don’t have to keep coming on and off.
For now I tested it with black gas because that’s what I had available. Surprisingly, it works well on black gas too. CO₂ should still be the proper final gas for the system, but the fact it works on black gas proves the mechanical concept.
Internal shot showing refillable cartridge and diagonal bolt/nut system installed
Last edited:
