Mosin Nagant闭锁间隙测量之山寨篇

检查Mosin Nagant

All matching serial numbers (receiver, bolt, barral, buttplate, bayonet)
Hex receiver may be better than a round receiver
Arrow-in-star (Tula), Arrow-in-triangle (Izhevsk)
Absolutely no crack on stock
Accessary: Bayonet (may not fit, try it on). Pouch. Multi-tool

1. Removing the bolt, chech chamber/magzine for rust
2. Crown. It can’t be wider than the rest of the bore. No counterbore.
3. Bore lighter (in receiver) to check the bore (look from muzzle). Do it slowly. No pitting. Grooves complete and deep. Lands stand proud.
4. Firing pin (depth) with multi-tool. Can NOT pass with smaller 3 notches. Must pass with larger 3 notches.
5. Headspace. Can NOT close the bolt with no-go or field gauge (Okie gauge).

SAAMI “Go” gauge – rim thickness = 0.066″ 1.6764mm
SAAMI “No-Go – rim thickness = 0.071″ 1.8034mm
Military Field (Absolute MAX safe) = 0.074″ 1.8796mm

首先看Receiver, bolt, buttplate和magazine的serial numbers全都match.
用摸心的Multi-tool检查firing pin也都正常.

还要检查闭锁间隙, 但又不想花25块钱买个小铁片.
俺就自己做了一个山寨的headspace gauge.

俺土人没打过摸心, 没有废弹壳. 就去买了A-zoom的snap caps.
先把弹底磨去一小块, 使其不受抓壳钩的影响.
不过如果是在店里测试, 小二不见得允许你拿大锤去敲抓壳钩

摸心的go gauge厚度为0.066″, No-Go 0.071″, field 0.074”.
用游标卡尺测量, 差不多刚好贴一层是go-gauge, 二层是no go-gauge, 三层是field-gauge.
也可以用可乐皮. 我测过, 基本是一样的. 用胶布主要是沾贴裁剪容易.

闭锁间隙中最重要的是no-go, 即headspace不能过大. 由于胶布会被压缩, 按上面做法作出的gauge实际上比no-go更严格一些.

用snap cap还有一个好处. 可以测枪管是否counterbore. 把弹头部分垂直向下放进枪
口, 弹壳不因该和crown接触. A-zoom的snap caps质量很烂. 我把它从枪口里拿出来,
弹头就有细微划痕. 不过这也刚好指出了接触位置, 是在弹头底部很接近弹壳口的部位.



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