Adjustable M1 Garand Gas Port

Perhaps like any good semi-automatic firearm, and U. S. rifle, caliber .30, M1 is a great one, the M1 Garand does not like firing blanks. However, when firing salutes on Independence Day, Veterans Day, or for military funerals, blanks are an obvious necessity. A variety of attempts have been made to modify the rifle to handle blanks reliably, often with less-than-perfect results. According to Bruce N. Canfield, Contributing Editor of the NRA Publications, this may be the reason the U.

S. military never officially adopted a Blank Firing Adapter (BFA) for the M1. To help solve this, I’ve developed a simple but effective solution. But first, a brief explanation of what and why.

As most of you know, the M1 is a gas operated, semi-automatic rifle, meaning when the rifle is fired, some of the expanding gas which (normally) drives a bullet is bled off the barrel and operates a piston—the operating rod in this case—which extracts and then ejects the spent case, cocks the rifle for the next shot, and feeds anew cartridge into the chamber; all in a fraction of a second. This is just the way John Garand designed it, for firing bullets or live rounds.

Garand, a Canadian, started working at Springfield Armory on improving American machine guns. There, about 1932, he was moved to designing the M1, the new semi-automatic rifle, which subsequently proved itself extremely well in World War II, and later, Korea. The rifle normally works very well, even in dirty combat conditions. It is The one on the left has been drilled and tapped for the plug described in the article. interesting to note that according to the NRA publication The M1 Rifle edited by Maj. G. H.

Drewry and Thomas E. Wessel, "The only instances of trouble in the M1 rifle manufacturing process, or with the finished product, occurred when some other engineer modified Garand’s design." In fact, General George Patton referred to the M1 as the greatest fighting weapon ever devised! Firing Blanks Now, when we ask the rifle to fire blanks with no bullet for the gas to push, things quickly become more complicated.

With no bullet to be pushed, little gas pressure develops in the barrel and there’s little pressure to bleed off and drive the operating rod. With not enough gas pressure, there’s little or no piston movement and little or no functioning, rendering the rifle into a single shot. We can’t have that now. What would happen to a five-shot salute? You don’t want five Marines firing and hand-cycling five rifles one at a time!

Because of problems like this many remedies have been envisioned, with most of them consisting of a restriction added to the muzzle. BFAs attempt to save enough gas to allow the rifle to function as a semi-automatic, yet not look funny to the casual observer. Problems can arise, however, when burned powder, not allowed to leave the barrel because of the restriction, accumulates. This leads to clogging gas ports, interfering with piston movement, or both.

Also, variations in blank cartridges and/or operatingspring tension from rifle to rifle may cause hiccups in the system. Here in the central part of Florida, my most frequent, regular customer has been the U. S. Marine Corps League, a group of volunteer patriots who honor our servicemen and women at parades and funerals alike. Maintaining their rifles for some time, we noticed all-too-frequent misfires, causing one or more Marines to have to suddenly cycle their rifles by hand.

Accordingly, I conceived a rather simple modification to their BFAs that allowed us to tune each rifle for a given load without excessive cleaning or

frequent swapping out stronger or weaker operating rod springs. I began by making a prototype, drilling and tapping an existing BFA for a 1" long, 3/8-24 slotted plug; itself drilled out 0.005" smaller than the "muzzle" on the original BFA. Then, two slots 0.028" wide were cut in one end by using a slitting blade in the milling machine. A hacksaw could also be used if one is careful enough. The open areas of the slots more than make up for the aforementioned reduction at the muzzle.

Before assembling the now-modified BFA, I first threaded the plug into a 3/8-24 nut to temporarily protect the threads and clamped the nut into a vice. Then, heating up the un-slotted end to a cherry-red color with an oxyacetylene torch, I drove a 9/64" Allen head wrench in about 3/16" deep, virtually forging a 9/64 socket for adjusting the plug.

Taking an M1 to the range with its now-modified BFA, I deliberately adjusted the plug out too far, exposing most of the slots to purposely allow too much gas to exit and preventing proper cycling of the rifle. As expected, the first round fired but didn’t eject the spent brass or feed the next round. So far, so good. From there, it was a simple matter of using a 9/64 Allen wrench to screw the plug in a little at a time, concealing more of the slots and reducing spent gas until the rifle finally cycled reliably.

I then applied a little Loctite on the threads to keep the plug in place. Obviously, a set screw into the side of the BFA would also hold the plug in place but I didn’t want any more visible modifications sticking out, particularly out of the sides! These shortened plugs for modified BFAs are now going into all the League’s M1s. For cosmetic reasons, I shortened the plugs a little but left the slots as they were.

Reliability has improved in every case, making for a reliable blank-firing M1 with minimal visible modifications. AG