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9 Makarov/ 550mm
Outer diameter 40mm!!
Bore diameter – land / groove
There are two basic diameters for a rifled barrel:
???? Land diameter (diameter across the field)
measured across the tops of the fields
it is a smaller diameter
determines the basic "caliber"
???? Groove diameter (diameter across grooves)
measured across the bottom of the grooves
it is a larger diameter
corresponds to the diameter of the bullet
Typical values for 9mm caliber
| Caliber | Land (mm) | Groove (mm) | Bullet diameter |
|---|---|---|---|
| 9 Luger (9×19) | ~8.82–8.85 | 9.01–9.03 | .355" (9.02) |
| 9 Brow (.380 ACP) | ~8.82–8.85 | 9.00–9.02 | .355" |
| 9 Makarov (9×18) | ~8.95–8.98 | 9.25–9.27 ❗ | .364" (9.27) |
???? It is the groove diameter that determines which bullet is safe.
Twist rate
It indicates the length at which the bore rotates 360°.
For example, it is written:
1:10" → 1 revolution per 10 inches (254 mm)
1:250 mm → 1 revolution per 250 mm
Common climbs
| Caliber | Typical climb |
|---|---|
| 9 Luger | 1:10" (254 mm), sometimes 1:9.8" |
| 9 Brow (.380) | 1:10" – 1:12" |
| 9 Makarov | 1:240–250mm (≈ 1:9.5"–1:10") |
???? Shorter pitch = faster rotation (for heavier/longer shots)
Example of writing
Barrel blank 9×18 Makarov
Land Ø 8.96 mm
Groove Ø 9.26 mm
Twist 1:245 mm, RH, 6 grooves
| Category: | Barrel blank |
|---|---|
| Weight: | 1 kg |
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