The most reliable method for modifying a mid-frame Smith & Wesson double-action revolver to chamber the .32-20 Winchester cartridge involves replacing the original cylinder and adjusting the forcing cone angle. Use a cylinder bored for 0.312-inch projectiles (not .308-inch) to prevent excessive pressure buildup. Replace the standard six-groove rifling with five-groove micro-groove rifling (1:16-inch twist) to stabilize lighter bullets effectively.
For optimal performance with cast lead projectiles, maintain a chamber throat diameter of 0.315–0.317 inches. The barrel should be rechambered with a minimum freebore length of 0.175 inches to accommodate powder expansion and prevent leading. Adjust the frame’s recoil shield by removing 0.040 inches of material to ensure proper cylinder rotation clearance when using full-power loads (e.g., 18 grains of 2400 powder).
Critical tolerances include the cylinder gap (0.003–0.005 inches) and the forcing cone angle (11 degrees included). Deviations beyond these specifications increase the risk of flame-cutting at the cylinder face. For handloaders, use CRS or BHN 12-16 lead with gas checks to reduce fouling in the forcing cone. Avoid lubricants containing graphite; alox-based compounds minimize bore contamination at higher velocities.
When modifying the hammer sear engagement, reduce the original geometry by 20–25% to compensate for the lighter trigger pull required by the .32 WCF’s reduced recoil impulse. Verify the cylinder stop engagement surfaces (0.010-inch radius mill cut) to prevent timing issues. For frame durability, heat-treat the cylinder stop notch area to Rockwell C 40–45 if employing +P+ loads exceeding 20,000 psi.
Technical Breakdown: Revolver Frame Variations in Classic Caliber Designs
Begin disassembly by removing the sideplate first–this exposes the hand and cylinder stop arrangement in both models. The .38 variant uses a shorter hand with a rounded tip, while the dual-caliber version integrates a longer hand with a squared end to accommodate the larger cylinder rotation arc. Failure to match the hand profile during reassembly will result in misfires or cylinder binding.
The cylinder stop geometry differs significantly between the two. In the .38 frame, the stop engages with dual notches cut at 90-degree intervals, while the dual-caliber model employs a single, deeper notch positioned 120 degrees apart. This adjustment allows the cylinder stop to engage both .38 and .32 chambers without modification–replace the stop only if wear exceeds 0.003 inches, measured with a micrometer across the working surfaces.
Examine the ejector rod timing as a critical step. The .38 configuration uses a fixed-length rod with a threaded end, requiring precise alignment with the extractor star. The dual-caliber revolver replaces this with an adjustable rod featuring a dual-thread design, allowing fine-tuning for ejector stroke consistency. Misalignment here leads to cases jamming under the extractor or incomplete ejection–verify rod protrusion against frame rails with a feeler gauge before final tightening.
| Component | .38 Configuration | Dual-Caliber Configuration | Tolerance Limit | Replacement Tool |
|---|---|---|---|---|
| Hand (extension) | 0.218″ L x 0.125″ W | 0.250″ L x 0.140″ W | ±0.002″ | Digital caliper |
| Cylinder stop (notch depth) | 0.080″ | 0.095″ | ±0.001″ | Dial indicator |
| Ejector rod (protrusion) | 0.156″ | Adjustable (0.140–0.175″) | ±0.003″ | Feeler gauge set |
| Extractor (star thickness) | 0.093″ | 0.085″ (recessed) | ±0.0015″ | Micrometer |
Replace the mainspring if compression drops below 18 lbs for the .38 version or 22 lbs for the dual-caliber variant–measured with a spring scale at full compression. The dual-caliber frame uses a thicker spring wire (0.058″ vs. 0.052″) to handle the heavier trigger pull required for reliable ignition of both cartridge lengths. Polishing the hammer face reduces friction but avoid removing more than 0.002″ of material, or primer strikes become inconsistent.
Check the barrel threads against a reference gauge: the .38 revolver uses a 14x1mm pitch, while the dual-caliber model switches to 16x1mm. Cross-threading during reassembly will misalign the forcing cone, causing accuracy deviations. If replacing the barrel, verify chamber throat dimensions–0.357″ for .38 cases and 0.312″ for .32–using a chamber cast or go/no-go gauge. Throat erosion beyond 0.005″ necessitates re-throating or barrel replacement.
Inspect the crane pivot pin for lateral play. The dual-caliber revolver integrates a hardened pin with a tighter fit (0.0005″ clearance vs. 0.001″ in the .38), preventing cylinder wobble under recoil. Lubricate the pivot with a light coat of grease designed for high-pressure applications–standard gun oil will shear under repeated firing cycles. If play exceeds specifications, replace the pin or ream the frame bushings to restore tight fitment.
Verify cylinder rotation timing by dry-firing with snap caps. The .38 model aligns the chamber with the forcing cone at 45-degree increments, while the dual-caliber version staggers alignment to 60 degrees. Staggered timing prevents case rim overlap during simultaneous extraction. If indexing feels stiff or uneven, disassemble the cylinder stop spring and clean the engagement surfaces–residue buildup here causes binding that mimics worn parts.
Final inspection should include a functionality test with dummy rounds. The extractor star must retract fully and reset crisply–listen for a distinct metallic click as each chamber aligns. If reset is sluggish, check the rebound slide spring tension (12–14 oz for .38, 14–16 oz for dual-caliber). Replace springs if tension falls outside these ranges, as compromised springs lead to light strikes or failure to fire.
Key Components Identification in Revolver Blueprints
Begin by locating the cylinder assembly–the heart of the firearm’s operation. This component houses the chambers and rotates to align each cartridge with the barrel. Examine the crane arm, the pivoting mechanism that allows the cylinder to swing out for loading and unloading. Ensure the locking bolt engages fully with the cylinder stop; misalignment here causes timing issues. Check the extracting system, including the star-shaped ejector and rod, for smooth operation. Any resistance during extraction may indicate accumulated fouling or worn parts.
The frame acts as the structural backbone, housing critical internal mechanisms. Pay close attention to the trigger and hammer assembly, where precise interaction determines firing reliability. The sear must hold the hammer securely in single-action mode, while the rebound slide ensures the trigger resets properly. Inspect the hand (pawl), which rotates the cylinder–excessive wear here disrupts indexing. Measure the headspace between the cylinder face and barrel forcing cone; deviations beyond 0.006 inches risk pressure hazards.
- The barrel is threaded into the frame–verify tightness to 25-30 ft-lbs torque. Loose barrels cause accuracy loss.
- Grip panels affect ergonomics but also protect internal parts like the mainspring and trigger return spring.
- Firing pin (frame-mounted or hammer-mounted) must protrude 0.055-0.065 inches for consistent primer strikes.
- Cylinder stop and locking bolt must engage simultaneously to prevent misfires under recoil.
Disassemble the yoke (cylinder support) to inspect the ejector rod bushing and ratchet. The ratchet’s teeth should show minimal wear; even slight rounding necessitates replacement. Lubricate the wolff mainspring and hammer strut with Militec-1 or grease–avoid petroleum-based products near grip panels. Reassemble with the trigger guard secured first, followed by the backstrap, to maintain proper tension on internal components. Test the double-action pull for smoothness; a weight of 10-12 pounds indicates proper mainspring tension.
Critical tolerances define performance. Use feeler gauges to measure:
- Trigger travel: 0.15-0.20 inches in single-action.
- Hammer fall clearance: 0.090-0.110 inches.
- Crane alignment: 0.002-0.004 inches lateral play.
Excessive specifications suggest worn bearings or improper reassembly. Replace the trigger pivot pin if rotation feels gritty–the original pin is case-hardened steel, not drill rod.
Final checks ensure longevity. Apply a thin coat of Lubriplate 105 to the cylinder stop notch and bolt engagement surfaces. Test the single-action timing by dry-firing; the hammer should fall 1/8 inch before cylinder rotation completes. For worn models, upgrade the hand to a reinforced aftermarket version and consider a lighter mainspring (85-95 pounds) for smoother operation. Recheck all screws with a torque driver: 18-22 in-lbs for grip screws, 25-30 in-lbs for sideplate screws.
Step-by-Step Disassembly Path for the .32-20 Winchester Revolver Using Visual Reference
Begin by ensuring the cylinder is empty and the hammer is in the fully down position. Press the cylinder release latch forward, then swing the cylinder assembly outward to the left until it locks open. Rotate the crane arm counterclockwise to detach it from the frame–apply steady pressure to avoid bending the yoke. If resistance occurs, check for debris near the pivot pin or lubricate with light gun oil before retrying. Once separated, the barrel group and cylinder can be cleaned without further disassembly, though deep maintenance requires removing the sideplate.
To access the internal mechanisms, remove the three screws securing the sideplate–start with the rear screw near the hammer, followed by the middle and front screws. Gently pry the sideplate away using a plastic or brass tool to avoid marring the finish; insert the tool into the notch above the trigger guard and lift while supporting the plate with your other hand. The mainspring, trigger, and hand components will now be exposed. Note the orientation of the cylinder stop spring before removal–stretch it cautiously to prevent deformation. When reassembling, ensure the sear engages properly with the hammer notch to avoid misfires.