Standard two-post plunger tube (top) and improved Christiansen tube with installation jig below it. (Photo: Gus Norcross)

The plunger tube resides on the left side of the frame between the top of the grip panel and the slide. It contains what Colt parts lists refer to as the "plunger spring assembly." The small plunger in the front of the tube rests on the slide stop with just enough pressure to keep the slide from locking open before the magazine is empty.

The larger rear plunger rests on the thumb safety. It keeps the safety on until the operator applies enough pressure downward to move it to the "off" position. The plunger tube is simply a steel tunnel attached by two posts that are swaged into chamfered holes from the inside of the frame.

Plunger tubes come loose. Every time a shooter operates the thumb safety, a slight amount of upward or downward pressure is applied to the plunger tube via the safety plunger. Over time, the thin swaged tubes that hold the assembly to the frame may start working loose. If the plunger tube begins pulling out of the frame, the safety plunger may end up on the outside of the thumb safety, locking it in the safe position - inconvenient in a match, deadly in a gun fight.

Use the jig in the installation kit to create the two new holes. Drill is a No. 38. (Photo: Gus Norcross)

Ned Christiansen at Michiguns, Ltd. (www.M-Guns.com) has introduced a heavy-duty plunger tube with double the number of attachment posts. Available from Brownell's as part number 100-003-822, this new tube should be much stronger than the original design. Installation requires two new holes to be drilled in the frame.

An installation kit (100-003-823) is also available from Brownell's that includes a drill jig, drill and plunger tube swaging support so the tube isn't damaged during installation. A swaging tool that will reach inside the frame to stake the ends of the posts is required.

I have used the Brownell's tool made from a modified pair of vise grips (080-806-500) for many years with great success. The plunger tube is filled with a 7/64" drill bit to prevent crushing the tunnel. Ned's drill jig makes installation with a small home drill press possible. Make sure you chamfer the inside of the two new holes in the frame before crimping. I used a 1/8" carbide ball-cutter on a hand grinder to do the chamfering.

Whenever you clean your 1911s, check the plunger tube for movement. It could save your life.

(A Maine native, Angus "Gus" Norcross is a retired National Guard Ordnance NCO with a passion for military weapons. A tank crewman during the Cold War with the U.S. Army 2nd Armored Division, he joined the Maine Army National Guard in 1981 and shot in military competitions with the Maine Combat Pistol, Combat Rifle and Machinegun teams at the state and national levels. In the 1990s, he served as a match-weapons armorer trained in the nuances of the 1911 match pistol and National Match M14 rifle. The proprietor of Angus Arms Co., a small gunsmithy that specializes in M1 Garands, M14s, AR15s, 1911s and FN/FAL rifles, he competes locally in NRA Highpower Rifle and IDPA matches when time permits. He currently resides on the Maine coast with his two Siberian Huskies and lovely wife Suzanne.)