April 05, 2013
By Gus Norcross
Anyone who knows me will tell you there is no greater advocate of the 1911 pistol than Gus Norcross. However, the 1911 is a machine, and any machine can fail if not properly maintained. In this article we consider one of the weak points of John Browning's design and how to repair it.
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 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 through the safety plunger. Over time, the thin swaged legs 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 gunfight.
Over 25 years of working on 1911 pistols I have seen my share of loose plunger tubes. Most owners never notice them. The top of the left grip panel provides additional support and a properly fitted grip may keep the assembly in place for a time even if it is loose.
The loose tube is usually easily removed with a pair of pliers and the mounting surface is cleaned to remove oil and dried gunk. Check the holes on the inside of the frame to make sure the edges are slightly chamfered so the legs of the new tube will have more surface area to grip when they are staked.
If chamfering is needed, a 1/8" ball cutter in a hand grinder will take care of it. I apply a drop of red Loc-Tite to each leg of the new assembly before positioning it on the frame. The Loc-Tite is simply extra insurance and fills small gaps or loose mounting holes.
For swaging the ends of the plunger tube legs in the frame mounting holes I have used a modified pair of Vise Grips (Brownell's 080-806-500) for many years with great success. The plunger tube is filled with a 7/64" drill bit or the Brownell's Plunger Tube Support (080-707-000) to prevent crushing it. A reinforcing block provided with the pliers fits over the tube to prevent damage to it from the steel Vise Grip jaws.
Whenever you clean your 1911, remove the left grip panel and check the plunger tube for movement. It could save your life.
The modified Vise Grip
The modified Vise Grip tool sold by Brownell's is shown with the plunger tube support and reinforcing block. Below the pliers is another tool made by Gun Runners and sold by Brownell's (634-000-001).
Here's the crimping jaw of the pliers, showing the hardened tip that swages the tube legs. This is a lot more convenient than using a punch for the job.
Prepare the holes
Prepare the holes by chamfering them with a 1/8" ball cutter. The wider hole gives more room for the leg to expand when swaged. This holds the tube better.
Apply red Loctite to the plunger tube legs before inserting them into the frame. This will help keep the tube stationary during thumb safety operation.
Insert the plunger tube support, position the reinforcing block and place the crimper tip over one of the plunger tube leg holes. Then just clamp down.
The Reinforcing Block
The reinforcing block prevents marring of the tube by the crimper jaw. The thin tube can easily be crushed if you don't use the block over it.
Make sure the crimper tip is centered on the end of the plunger tube leg before crimping. You want the plunger tube leg to expand evenly around the frame hole.