By Robert G. Segel
A new modified Vickers lock is now available that addresses the two weakest breakage-prone lock parts and ensures reliable operation regardless of ammunition used.
Four friends and avid full-auto devotees from Nevada got together and created a company called SOG-LLC, Inc. Billy Conn, Bill Stojack, Robert Smith and Jon Word wanted to create a company that was not profit driven. They wanted to cater to the Class 3 community from an enthusiast’s point of view in terms of service and need while striving to keep the traditions of the original designs using modern materials and manufacturing techniques when possible. The four men combined their particular skills to form SOG-LLC. Billy Conn and Robert Smith act as business managers, Bill Stojack is the armorer and machinist, and Jon Word is a highly skilled mold maker.
Initially, they assembled four semiautomatic Vickers and had trouble with the ammunition, primarily due to light strikes on the primer – a condition common with Vickers. Surplus .303 ammunition, from many different manufacturers, is exasperatingly inconsistent with hard primers resulting in unpredictable reliability and consistently broken firing pins and leaf springs (firing pin springs). These two problem areas are the reason that so many extra leaf springs and firing pins were included in spare parts kits. Metallurgy of the time caused wide variations in performance of the lock spring and they are prone to weakness and breakage as confirmed in ensuing lock spring compression tests. The firing pin also did not have adequate mass to overcome hard primers resulting in breakage. Thus, a weak lock spring and an inherently light firing pin weight, combined with old ammunition with hard primers, equal an unacceptable reliability of function.
Frustrated by this quandary, Jon and Bill analyzed the problems and their causes and embarked upon a plan to research and diagnose the difficulty. They identified what the problems were but were not clear upon the solution. Their inspiration to solve the problem came from the Czech 30 (t) Vickers aircraft lock that used a coiled, rather than leaf, spring and had a reputation of being extremely reliable under many adverse conditions. They did not want to manufacture a completely new lock body. By studying Czech 30 (t) lock drawings, they devised a method whereby they took the mechanics of a Czech 30 (t) lock and applied it to the standard Vickers lock body.
They designed and manufactured a set of new parts to replace the original leaf spring, firing pin and safety sear. These new parts were the firing pin, firing pin coil spring, safety sear, safety sear axis pin, plunger, plunger coil spring, plunger plug, split keeper pin and two blocks to hold the firing pin coil spring and the lock trigger coil spring assemblies.
In trying to keep with the traditions of 19th century technology and manufacturing processes, in the first prototypes, both spring blocks were silver soldered and riveted into place on the modified original lock body. But it was felt that this caused too much heat to the lock body. The two spring blocks are now TIG welded and riveted to the lock body.
The steels selected were chosen for their ability to perform in the given applications. The trigger reset block is manufactured from O-1 steel as is the safety sear. The safety sear is heat treated and double drawn (tempered twice) to relieve stress and ensure long life.
The firing pin is manufactured from S-7 steel, heat treated and tempered. This steel is used because prior to heat treatment, it machines easily, and after heat treatment, it can still be machined with carbide tooling. S-7 steel takes impacts well and will give the firing pin a long service life. Each firing pin is made by hand and several steps have to be done with a file to achieve the proper contours and transitions. Approximately four hours is spent on each firing pin alone. Eventually, some of the process will be done on a CNC machine, but they will never get away from the “file to fit” work.
The firing pin spring is a silicone alloy die spring designed to give a 100,000 cycle service life. The trigger reset spring is a standard M16 spring, making it easy to find spares if that should become necessary.
Small Arms Review was given the opportunity to test the new lock using three different Vickers gun in two different calibers. This test was conducted in two phases with one of them using the new lock on the firing line at the April Knob Creek shoot using two different Vickers guns. In this first test at Knob Creek, using a variety of British, Greek and Indian .303, the new lock was simply dropped into two different Vickers and ran without a single problem digesting everything put through it. In total, 3,000 rounds of .303 were used.
In the second test at a different time and at a different location, the new lock was assessed using a different caliber; in this case, Yugoslav 7.62x54R ammunition was used. A 7.62x54R barrel and a modified feedblock were put in a standard British Vickers Mk I water-cooled machine gun and a modified 7.62x54R lifter was placed on the new lock. 1,500 rounds were consumed without a single malfunction. In all, using three different Vickers in two different calibers, the new coil spring Vickers lock fired 4,500 rounds without a single failure due to the lock and proved not to be caliber sensitive. A very admirable performance.
SOG-LLC also makes a stainless steel Lewis gun gas piston to replace the corroded gas pistons inherently found in Lewis guns. They also restore and re-wat full autos. For more information, they may be contacted at: SOG-LLC@earthlink.net.
|This article first appeared in Small Arms Review V9N1 (October 2005)|