3-Point Jam
Reliability in a defensive sidearm is paramount. Reliability comes first, and everything else is a distant second. No man-made machine is, or can be completely reliable over its useful life span. Sooner or later, there will be a malfunction or parts failure, but we can take steps to reduce the possibility of malfunctions with a little understanding of how the gun works, and a little attention to detail.
One malfunction in a thousand is a fluke. One in 500, and we start to get a little nervous about the gun. One in a hundred, and the pistol is virtually useless, except for range work...and even that gets to be a hassle.
Feed stoppages...Probably the most frequent issue... second only to extraction/ejection malfunctions...and most often these are a failure to go to full battery. Rather than go into the standard advice to adjust the extractor...polish the breechface...get good magazines... polish the ramp and throat...ad nauseum...I'll assume that the reader has already addressed these areas, and is at a loss to determine the cause of his woes. Most pistols these days come with the throat and ramp already done and usually well-executed. Many pistols have been ruined by over-zealous work in these areas. Unnecessary work.
Stem bind is usually the culprit in a failure to return to battery. Actually, that's misleading, since a little stem-bind is always present in the 1911. That's what slows the slide as it goes to battery and prevents damage to the lower barrel lug and slidestop crosspin, and gives the round time to get under the extractor. Excessive stem bind is more accurate...or what is technically known as the "Three-Point Jam"
Three points...binding between the breechface, the barrel throat, and the underside of the barrel chamber. Forget what you've heard about the overall length of the round for a minute. If the 1911 is correctly set-up, it's more forgiving of cartridge length variation than many would have you believe.
Consider the barrel link. If the link is correctly fitted to a correctly shaped and in-spec lower lug, there probably won't be a three-point jam. Why?
As the cartridge strips from the magazine and strikes the barrel throat, it pushes the barrel forward. Due to the tilting-barrel design, when the barrel moves forward...it also moves upward. If the barrel is correctly fitted, this upward movement is provided by the front radius of the barrel being cammed up by the slidestop pin, and the rise is gradual.
Want to feel your pistol feed more smoothly than you ever imagined that it could? Load 3 or 4 rounds in a magazine...lock the slide to the rear... push the muzzle against the edge of a table, and ride the slide forward... not in slow-motion...but not at full speed either. You won't feel a bump... no hesitation...no stem bind as the round chambers. None.
Tripp Research has attempted to address this issue by designing a magazine that presents the cartridge at a lower angle as it enters the barrel throat. While this approach will often work...it's a band-aid that masks the true nature of the problem...and it doesn't always work.
Now, consider the incorrectly dimensioned lower lug. If the link is the correct length for vertical lockup, where the lower lug and slidestop pin bear the load of the vertical lock...but the link is long enough to hold the pin away from the front radius, you have the makings of a 3-point jam.
The condition is known as "Riding the Link". When the barrel rides the link around the lower lug's radius, it causes the barrel to rise early in relation to the slide's position...when the round is just entering the throat. In addition to rising too soon, it moves upward too abruptly, which puts the slide and cartridge even further behind in its approach to battery. Bang! A three point jam has just taken place. (Many factory-built pistols these days have this condition.) When you get a pistol that seems to feed everything that you put in it without a glitch...look at the link to see why.
Think back to your childhood, when you'd find a suitable stick to play "Pole Vault" with. Remember how the dynamics changed the higher you placed your hands on the pole? There was a point that you wouldn't be able to vault, no matter how fast you ran. Same principle.
Okay...You've plunked down your long green for a factory pistol that doesn't have a correctly dimensioned lug...The barrel is riding the link, and your pistol produces a return to battery stoppage often enough to destroy your confidence in it. You don't have the money for a gunsmith to refit the lug or another barrel...and you either can't afford or justify buying another pistol on the chance that this one will be "right". What to do?
Often the advice is to install a heavier recoil spring in hopes of using enough force to overcome the jam...This is not only the wrong approach, it usually doesn't completely eliminate the stoppage...It just makes it less frequent...at least until the recoil spring starts to get tired. You still have a nagging doubt that the gun will perform in an emergency. The ramp and throat have already been tended to.
There are a couple of approaches that will usually work. If the barrel is standing on the link in vertical lock, you can try a shorter link. You're limited to about .003 inch shorter here. If the shorter link will make it around the front radius without getting into a bind, you can go with that and likely cure the problem. A shorter link will have the effect of unlocking the barrel a little earlier...which can possibly be an extraction issue if it unlocks TOO early..while the chamber pressures still have the case expanded, but this will probably happen only if the unlock timing is right on the line anyway.
If the barrel is correctly locking via the bottom of the lug and the slidestop pin...and the lower lug is dimensioned so that the link is holding the pin away from tha frontt radius, you can't use a shorter link unless you modify the bottom of the lug...which will undermine your vertical lockup.
You can, however, modify the link a little by elongating the slidestop pin hole at the top to get the barrel off the link and onto the lug where it belongs. The barrel rise will be delayed, so that the slide will be a little further forward and the round a little deeper into the chamber...and at a shallower angle. The unlocking and linkdown timing will be unchanged, since the BOTTOM of the link's hole determines where and when the barrel will begin to unlock...and your stem bind will be substantially reduced.
On this modification, you are limited to about .005 to .006 inch of elongation, and even if it doesn't put the radius on the crosspin, it will put it much closer...relatively speaking. The probability of correcting the three-point jam with this is high...about 95%. If the lug rides on the pin, the chances of success are even higher. Elongating the hole even as little as .002 inch will usually produce a dramatic difference...so take it a little at a time. No more than necessary. This will make it a trial and error exercise.
To do this, I use a Dremel and a 3/16ths chain saw sharpening stone. The stone is slightly smaller in diameter than the slidestop pin, so you'll need to use a slight "rocking" motion to make the radius of the hole the same size as the pin. Otherwise, the pin and link will bind. You'll also have to be careful to keep the stone square to the link as you cut. If the hole isn't straight and true, the barrel will still ride the link, and possibly cause a side-load and a bind in that direction.
Use light pressure, so that instead of cutting, you are actually polishing the material and removing very little at a time. Be careful not to enlarge the hole farther than the sizing of the bottom half where the slidestop pin will fit into. Use a scrape to deburr the sides of the hole, paying attention to the modified area in the top. The tip of a good pocketknife will do. Measure the size of the hole with a dial caliper, and re-measure it often as you go. Test the feeding at .002 inch intervals, and stop when you fix the problem. A little is good...A lot ain't necessarily gooder.
