PISTOLS CAUSES OF FAILURE AT 100 FOOT SETTING

1. The most common causes of failure of pistols to operate satisfactorily when subjected to standard functional test at 100 ft. settting (Chapter V, Paragraphs 6 and 7) are:

(a) Burr on release plunger. This is caused by repeated test firing. Better control of ma-terial hardness has been obtained in recent manufacture to that improvement in this res-pect should be noted.

(b) Radius on ball release shoulder of release plunger not of uniform throughout the cir-cumference of the plunger head. This is caused by improper grinding during manufacture. It results in erratic firing pressures.

(c) Improper assembly of depth setting sleeve. See instructions noted in paragraph 13 (n).

(d) Binding of hydrostatic piston stem and key in the adjusting bushing due to corrosion. The practice of using Polar Type, Rust Preventive Compound, Navy Department Specifi-cation 52-C-18, Grade II, on overhauled pistols should help to control this condition.

Blue indicates exterior - Red indicates interior

Piston cross section.

(e) Displacement of the index pointer, at depth setting, with respect to its original cali-brated position on the index pointer carrier. This is caused by failure to lock the index pointer screws securely with solder on the Mark 6 Pistol and Mark 6 Mod. 1 Pistol of early manufacture. Failure to tighten set screws securely on Mark 6 Mod. 1 Pistols having this type of fastening will permit index pointer to move from its originally calibrated position.

(f) Leakage at soldered joint between bellows and hydrostatic pistol and bellows and bel-lows extension.

(g) Binding of hydrostatic piston stem in bore tube on Mark 6 Mod. 1 pistol. Action has been taken to eliminate this defect in recent manufacture by reducing the diameter of the end of the hydrostatic piston stem.

(h) Seating of the ball valve in deep firing mechanism of Mark 6 Mod. 1 Pistol when poin-ter is set at "0-300". Usually this is caused by end coils of valve spring not being proper-ly set down.

(i) Depth setting spring has become "set", due to prolonged compression.