Posted: Mar 28th 2010, 10:55 AM
I already mentioned in the other thread about selling my PT1911, but I thought I'd give some specifics, just in case anyone finds the information useful, or not. It's up to you.
One of the things they spent a great deal of time on in the gunsmithing course has to do with 'loose breach'. Didn't even know what that was until I took the class. For those who may not know, this refers to how much forward/backward play there is between the barrel and the slide when its locked up. Take the slide off your gun. Put the barrel in and move it so that's its in the locking grooves. Now see if it will move back and forth. If there is motion there, that's called loose breach. There will almost always be some. It can be made zero, but it requires a LOT of hand fitting.
When there is play between the barrel and slide in locked position, it can affect the reliability of the gun, but the biggest affect is on the gun's life expectancy. When the slide goes shut on a loaded round, the slide is pushed up against the breech hood, so that the lugs on the barrel are engaging the back side of the locking slots in the slide. When the round fires, the friction of the bullet being forced into the rifling makes the barrel accelerate forward briefly. At the same time, the slide is accelerating backward. The result is the barrel and the slide move apart, very fast, until the barrel lugs engage the front edge of the slide locking grooves. If there is excessive play it increases the distance they travel in opposite directions before the lugs engage. Obviously, the further they travel before coming together, the more violent the encounter. This can put a great deal of stress and wear on the parts. The instructor said he's seen guns were this was so bad that the faces of the lugs and slots had actually been rolled back. Eventually they will fail. And when they do, the slide and barrel are both ruined. An expensive state of affairs in any gun.
Having said that, the instructor in the course said how much play is allowable depends on how much the gun is used. If its a home defense gun, left in a drawer and only fired occasionally, you can get by with up to .008 of an inch movement. But if the gun is to be fired a lot. They recommend .002...max. My PT1911 measured out at .013. It was so loose that if I laid the barrel in the slide in locked position and shook the slide back and forth, the barrel would clink. I was told that gun could fail in as few as 500 rounds.
It just had to go. Period.
