De-Farbing the BAR: Gas Regulators
Date Written: January 2009
Author: Chris Guska
One of the top 3 dubious components used by WWII Reenactors on their Browning Automatic Rifles is the Gas Cylinder Body / Regulator Assembly. This is universally applicable to all WWII Reenactors, ETO, MTO and PTO alike.
There are 3 types of Gas Cylinder Bodies, with only one of them being “WW2 Correct”.
The “WW2 Correct” pattern of Gas Cylinder Body, Part #C64296, consisted of a threaded tube with different sized holes drilled in it at 0 degrees, 120 degrees and 240 degrees.
The regulator has 3 positions, indicated with progressively larger circles marked on the face of the part. The BAR gunner was to adjust the gas regulator to the setting that reliably operated the weapon compensating for fouling, mechanical wear and external temperature. The selected position was moved such that the circle indicating the gas port size is at the 12 oclock position.
C64296 was problematic due to it being very difficult to quickly adjust in the field without the use of tools. A split locking pin B19649 was used to retain the gas cylinder body in position, requiring the use of the combo tool or other small round punch type object to dislodge the lock to change the position of the body to a larger gas aperture setting. The complete assembly of C64296 and B19649 was Assembly B147500
B147500 installed on a WW2 Gas Tube, with the split pin locking it into position.
There are several variations in style of the early gas regulator, drawing back from WW1 production through WW2. The early style were made with a solid, unvented face and part number C64077. The vented, style is part number C64296.
By 1923, the vented gas regulator was developed with the M1918a1 and "idealized BAR" programs. Both styles of regulators saw use in WWII and were listed as acceptable as late as 1942 in FM 23-15. WWII new production gas regulators were of the vented style.
In Mid 1944 a request was made to the Ordnance Department to develop a new Gas Cylinder Body Assembly that could be easily adjusted without the use of tools. A new Body and Regulator assembly was designed, tested, found to be generally satisfactory and recommended for adoption in August 1945 for use on future new production of M1918a2s. Existing stocks of B147500 were to be used until exhausted. This new regulator was assembly number 7162349.
. Despite being designed and “recommended for adoption in August 1945”, the late style Gas Cylinder Assemblies are incorrect for use by WWII Reenactors. 7162349 was not manufactured for the first time until 1952 by Tool & Metal Specialty MFG co of NY, NY These late style adjustable Gas Cylinder Assemblies are most correct for late Korean and early Vietnam war impressions.
In 1955 an improved version of the adjustable regulator was adopted, part number 7267819. This improvement incorporated a full detent ring rather than half ring key, in addition to omitting the body lock roll pin.
Comparison of WW2 B147500 on top, Post 1955 7267819 middle, and post WW2 1952+ 7162349 bottom.
To utilize the B147500 regulator, you must have an unmodified gas tube. Gas tubes remained unchanged from WW1 through WW2 with minor exceptions. With the introduction of the late style adjustable Gas Cylinder Assemblies, the Ordnance Department instituted a program of modifying existing stocks of gas tubes. The modification consisted of milling away the area between the 120 and 240 degree Gas Regulator Lock slots such that you cannot use the early gas regulators in them. This modification was done most likely to prevent soldiers trained on the old style regulators from adjusting the new regulators in the same manner. With the modification, the regulator will only lock into the tube with the key in the 12 oclock position, so that the single gas port in the body of the regulator will be aligned.
The tube you need to use the WW2 regulator properly is on the left. The modified, postwar tube is on the right.
Ballou, James L. Rock in a Hard Place, The Browning Automatic Rifle. Collector Grade Publications, 2000.
Knott, George. "BAR Gas Systems." E-mail interview. 2 Jan. 2009.
United States. War Department. FM 23-15 Browning Automatic Rifle M1918a2. 1943.
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