Flash Hiders-Silencers

May 2016-D

REPORT OF THE INFANTRY BOARD #1675B, FLASH HIDERS-SILENCERS

FOR U.S. CARBINE, CAL. .30, M1, dated 21 FEBRUARY 1945

Although the T23 Flash Hider had been developed by January 1945, the Infantry Board at Fort Benning, Georgia, tested two varieties of a combination “Flash Hider – Silencer.”  The two types were identified simply as “small” and “large.”

 

“Small Flash Hider:  This hider consists of a metal tube, to the rear end of which are fastened clamps for attaching the device to the carbine.  The metal tube is filled with washers made of wire screen, approximately 30 mesh. Each disc has a hole in the center to allow passage of the bullet.  The discs are held in place at the rear of the tube by the seat, which fits on the muzzle of the carbine, and at the front end by a threaded steel cap which screws into the tube.”

 

Below photo shows the small hider attached to an IBM carbine. “The small hider adds 1.06# to the weight and 8.6” to the length of the carbine.”

 

“Large Flash Hider: The body of this hider is a large metal tube, approximately 2.2” in diameter.  A smaller metal tube passes through the body, and on the rear end of this tube are fastened the clamps for attaching the device to the muzzle of the carbine. The small tube has a series of brass baffles in it, with spacers separating the baffles.  In the rear third of the tube, the baffles have considerable space between them, while in the front portion, the baffles are separated by approximately 0.15”.  The tube has a series of holes punched in it in the rear portion.  Around this part of the tube is wrapped wire screen.  The holes permit some of the gas trapped behind the bullet and the baffles to escape into the space between the small metal tube and the body of the silencer.  A ¼” escape hole is provided in the front of the body. This hole may be closed with a screw when desired.”

Below photo shows the large hider attached to the same IBM carbine. Another carbine (with prototype bayonet lug) is shown for comparison purposes. “The large hider adds 2.16# to the weight and 8.6” to the length of the carbine.”

It is interesting to note that both of these devices, as shown, would not fit on a carbine equipped with a bayonet lug, although the testing of these occurred months after the bayonet lug had been standardized.

“The method of fastening the hider to the carbine is the same on both flash hiders.  A conical seat (C) fits over the muzzle of the carbine.  Approximately 4” to the rear of the seat is a pivoted clamp (D), which fits over the top of the barrel and is tightened and held in place by a wing nut (E).  A “U” channel connects the seat and the clamp, and is formed from a part of the tube.  A flat wedge (F) slides transversely through the lips of the “U” channel. This wedge slides in behind the front sight (B), thus preventing forward movement of the hider.  A flat spring (G) bears against the large end of the wedge, thus forcing it in.  This spring is pivoted and can be dropped down away from the wedge to permit moving the wedge away from behind the sight.”

“Top view of small and large flash hiders.  The small hider (at bottom of photo) has the wedge and clamp closed, while the large hider (at top of photo) has the wedge and clamp open, ready for installment to a carbine.  Figure A. Note damage to body of large hider, temporarily repaired.

Testing began on 22 November 1944.  As might be expected, the rather crude method of attaching the hiders to the carbine created problems. “It was found that small burrs on the muzzle of some carbines would prevent seating the flash hider far enough to permit putting the wedge in place.  When the burrs were dressed down, the hiders could be installed…

 

It was found that the flash hiders were not exactly parallel to the bore when installed on these carbines.  In some cases, the flash hiders were considerably off parallel.  When these combinations were fired, the bullets struck some portion of the flash hider, giving very erratic results…

The hole in the end cap of the flash hider is approximately 0.375” in diameter.  The carbine bullet is approximately 0.305” in diameter, leaving a net clearance of 0.07”.  If this is evenly divided, i.e., the bullet is centered in the hole, there is only about 0.035” clearance around the bullet.  This is approximately 1/32”.  The flash hider extends approximately 8.6” beyond the end of the muzzle.  A difference in angle between the hider and the bore of about 14 minutes will cause the bullet to dig against the end cap.”

Photo left: “The small flash hider was damaged during night firing.  The majority of the screen washers were distorted, and the tube of the silencer was bulged in several places.

Photo right: “The large flash hider slipped off the muzzle during early stages of the firing and was damaged.  This damage was repaired enough to permit attaching the hider to the carbine.  During firing it was again damaged, practically beyond repair.”

The firing tests showed other problems:  “When the carbine is fired with the large flash hider attached, a considerable amount of gas and smoke comes out of the breech of the gun, especially when the screw is left in the gas escape port in the front of the hider.  When firing on a calm day, enough gas and smoke comes back into the gunner’s face to cause irritation of the eyes and lachrymation.  After approximately 3-5 shots in rapid succession, the gunner has to stop until his eyes stop smarting.  The hider was damaged before any firing was done without the screw in the escape port.

The large flash hider is of such size that it blocks most of the front sight.  When using the low position of the “L” type rear sight, just the tip of the front sight is visible over the top of the flash hider.  When using the high rear sight, the tip of the front sight is about even with the top of the flash hider.  This makes it difficult to aim the carbine in the normal manner, especially if it is necessary to hold slightly over a target.  The small flash hider blocks off about ½ of the front sight, and is not as objectionable as the large hider in this respect.

If the large flash hider is hot from firing or exposure to the sun, a considerable amount of mirage, or heat radiation will be present, which distorts the target image. 

Because of the large number of baffles and spacers, it is not easy to disassemble and assemble the flash hiders.   If it is necessary to clean the flash hiders, it is not a job that can be done quickly and easily.  If patches are pushed through the hider, there is considerable danger of fouling the patch and leaving it in the flash hider.  If the flash hiders are cleaned without disassembly, there is a possibility of partially filling them with water, cleaning fluid or oil. 

 

As received, both flash hiders gave some difficulty due to improper alignment, resulting in bullets striking the end cap.  As noted…the flash hiders did not fit exactly the same on all carbines, indicating that possibly some adjustment should be provided so that a given flash hider could be fitted to a given carbine.”

It wasn’t all bad news: “The gun with the small flash hider made less noise, but the large flash hider made the least noise.  The large flash hider very materially reduced the report…The carbine bullet makes considerable ballistic noise (bullet “crack”), which is not affected by the silencer…It is possible that the use of one of these silencers in conjunction with a special low-velocity load for the carbine might provide a near-silent weapon.

The small flash hider materially reduced the flash.  It is estimated that the flash with hider installed was about 25% of the flash from the plain gun.  Both hiders were damaged before the test could be carried to completion.

Test Officer’s Discussion: 

1. Both devices appear to have desirable silencing and flash hiding qualities.  In return for this, certain undesirable properties have to be accepted:  increased weight, increased length, partial blocking of the front sight, partial blinding of the gunner, etc.
2. In some conditions it might be that these desirable features would overbalance the undesirable qualities listed above.  However, the worst feature of the devices is the difficulty of obtaining and holding the high degree of parallelism needed between silencer and carbine barrel. Until this difficulty is overcome, the Test Officer does not believe that these devices are practical for field use.
3. A silencer and/or flash hider might be a very desirable accessory for the full automatic carbine recently tested by The Infantry Board.  Subject flash hiders were damaged before they could be tried on the automatic carbine.”

Finally on 21 February 1945, “The Infantry Board recommends that no further consideration be given to the subject flash hiders.”

The Rock Island Arsenal museum has an example (under glass) of a carbine modified with a silencer, that is a much more compact and rigid design than those tested in 1945.   Details of its fabrication are unknown by the museum staff.  The overall length of the carbine is 36 3/8” with a 12” barrel.  It is Inland 926787.  The museum description states that it is “manually operated.”  Note that the inertia block for the slide was apparently sacrificed when the stock and handguard were shortened, and the silencer attached to the barrel.  Note also that a long and tall ramp-type rear sight has been installed.

Thanks to Jim Mock for supplying this photo and details.

Marty Black

I have a 1942 Inland carbine in the 179000 range that has what appears to be a muzzle cap and a cone shaped muzzle. Also, the front sight is somewhat milled away on the front. Any ideas?

By the way I tried to send photos but have no idea how to load them. Advice?