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Posted: 4/22/2007 8:01:59 PM EDT
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The specified load (spring force) for the USGI M14 magazine spring is 5.5 pounds + 0.75 pounds at a compressed length of 5.5 " (unloaded magazine). However, the magazine spring will perform satisfactorily (no malfunctions) down to 4.5 pounds force at 5.5 " length. Three USGI M14 magazine springs were placed into a vertical shaper for a gymnastication test. Each spring was cycled at a rate of 116 strokes per minute. The spring force was tested after each spring had been cycled 6,655 times. The results were 6.1, 6.1 and 5.75 pounds each at 5.5 " length. The spring force was tested after 10,000 cycles. The results were 5.1, 5.75 and 3.9 pounds at 5.5 " length. One spring measured 5.25 pounds at 5.5 " length even after 12,000 cycles with bad distortion. The springs were found badly distorted at 10,000, 12,000 and 14,751 cycles, respectively. Ten magazines were stored loaded for five years. After the first week in storage, the magazine spring force was found to range from 5.1 to 5.6 pounds at 5.5 " length. After five years of loaded storage, the same ten magazines were test fired with six loadings (120 rounds per magazine). The magazines were then disassembled and the spring force measured. The results were 4.6 to 4.75 pounds. There was no malfunction of any magazine. Ten magazines were stored unloaded for five years. After the first week in storage, the force for each spring ranged from 8.3 to 8.8 pounds at 5.5 ". After five years, the same ten magazines were loaded and fired six times each (120 rounds per magazine). The force for each spring was measured. The results ranged from 5.0 to 5.25 pounds at 5.5 " length. There was no malfunction of any magazine. References: 1) USGI drawing C7267078 2) Evaluation of Pretreatment Processes and Long-Term Storage On Magazine Spring For the M14, 7.62MM, Rifle. Springfield Armory: February 1966. |
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