1911 Controlled Feed
We all know that the 1911 pistol operates on the controlled feed principle…but how many understand exactly what that means…and exactly what is involved?
Think of it like a bucket brigade used back in the day before pumper trucks were available for putting out fires. Each bucket of water was handed off to the next man in line, and wasn’t released until he had a grip on it instead of throwing it at him, hoping he would catch it without spilling any water. A controlled hand-off. Lterally waiting until the bucket is under the control of the next station before releasing it.
That’s kinda the way it works. If at any point in the feeding phase, the cartridge is “thrown” at the next point of contact…a malfunction is almost certain. Even if the gun finishes the feed and return to battery, that’s not a guarantee that it did it under full control.
Another way:
That it functions doesn’t mean that it’s functioning properly. Improper function affects both reliability and durability. It may…or may not…feed and go bang…but improper function can and does cause premature parts failure. In this case, it’s usually the extractor that suffers. While a failure to feed or go to full battery is bad in an emergency, it’s usually remedied quickly. Not so with a failed extractor. A failure to extract isn’t something that you want to happen during a life and death confrontation.
Let’s break it down step-by-step.
The breechface hits the round in the magazine and starts to push it forward. As the round moves forward, the bullet nose makes contact with the feed ramp, which resists it and holds it in contact with the breechface.
The round noses up on the feed ramp, and…with a proper magazine feed lip design..also starts to rise at the rear, pushed by the round under it…which is pushed by the magazine spring. The cartridge is in positive contact at three points with the breechface…the feed ramp…and the cartridge that’s underneath it.
The bullet nose glances up on the feed ramp…still rising at the rear…and contacts the upper portion of the barrel chamber. It should be noted at this point that the barrel ramp…or “throat” as its come to be called…isn’t a bullet guide. The bullet nose shouldn’t touch it below the top corner, as it glides across and starts to break over to horizontal.
The breechface is still in forced contact with the rim, and as it rises at the rear, the magazine hands it off to the extractor. This all happens within a very short distance, because once the slide covers the rear half of the magazine, the front of the next round is depressed, and can’t further influence the feeding round other than to support it at the bottom.
The round gliding over the top corner of the barrel ramp places a positive downward force on the barrel…keeping it in bed and maintaining as low an angle as possible. As the cartridge breaks over to full horizontal, the rim is completely picked up by the extractor…the magazine finishes releasing it, completely relinquishing control…and the round chambers smoothly. If the pistol is feeding exactly the way it should, you’ll scarcely be able to tell that it’s chambered a round. The sound will be the only real indication that it’s happened.
The features that properly allow true controlled feed are the angles involved. Angle of the feed ramp and the barrel ramp. The angle of the breechface…which isn’t supposed to be a straight-up 90 degrees to the center rail…something that has been noticed by anybody who’s looked at the prints on the original patents…but isn’t full understood. No. It’s not because the barrel tilts at the rear when it’s in battery, though that’s the general assumption. The angle is 89.8 degrees, with no plus or minus tolerance…which suggests that it’s pretty critical to any machinist or toolmaker who sees it.
Yes, then there is the tipping angle can be affected by several factors, Cartridge overall length, if too long can cause the cartridge’s case head to not slide up the breech face as it tries to tip into the chamber. Then there is bullet shapes, where the old ball ammo had a FMJ slick rounded nose that helped to guide that cartridge to battery. Now with the use of hollow point and flat point ammo, yields a wider nose profile, this can increase the tipping angle length, therefore they require a shorter cartridge overall length the cycle up and tip into the chamber enough to allow the rear of the casing to slide up the breech face and under the extractor hook as it rides into battery!
There is some great pictorials listed at the 38Super.net to further help with explantions.
http://38super.net/Pages/Overall%20Length.html
Another great article Hunter
As always Mr Travis, very good article. Why do you think JMB used that particular breech face angle of 0.2 degrees shy of a true right angle? Thanks for all your work
JH
Mr Travis, funny you should mention controlled feed along with magazine feed lip style and the required D shaped dimple on the follower. All of our side arms were TRP 1911’s, our armorour would ALWAYS set up our pistols as you advocate, in particular the magazines we used at that time, were the gi feed lip design supplied from checkmate, ammo was 200 grain round nose at 975 ft/ sec……..they would do a complete reliability set up of the trigger works, usually Cylinder & Slide kits……. .022 hammer hooks with trigger pulls set at 4.74 lbs, 5/64 th radius firing pin stop, no shok buffs, however all the armorours believed in full length guide rod with wolff 17.5 variable rate springs, single side tactical safety. The barrel bushings were clearanced at .002 vrs .001 for better field reliability……after all was said & done, these weapons were extremely reliable, never a malfunction, very smooth. Sand bagged, these side arms would group at 1″ or less at 25 yrds. I still set up my 1911’s per this set up ……….. i really enjoy your aticles, they always make sense, and they 100 % agree with the armorours that made everything work………
Semper Fi