Saturday, April 25, 2009

1911 Feed Ramps and Magazines

Knowing there are some 1911 aficionados among us I found these two articles of value. The first is a link to someone doing a magazine comparison as it effected a Para. But the variety of magazines he looked at is interesting. I'm not sure I agree with all his conclusions (I'm a huge Wilson mag fan) but they were interesting to consider.

Then I've also included the link and text of a conversation mentioned in the mag compare article with regard to controlled feeding on a 1911 and why you SHOULDN'T polish your feed ramp. Interesting to say the least.

Hope you find them of use.

Magazine comparison:

Controlled feeding in a 1911:

Controlled Feed Principles by 1911 Tuner in the Forums

Guess it's time to do a thread on the Controlled Feed principle. Seems that many don't have a full grasp on exactly what it means and how it works. So...since part of the mission of the forum is to educate...Here ya'll go.

The system is actually pretty simple. It's in understanding how it works that throws so many people off the trail. Simply put...The cartridge must remain under full control of the gun from the time the magazine is locked in until the empty case clears the ejection port.

Much is made of the angled feed causing problems. Much ado about nothing. It's not supposed to feed in a straight line. Or another way...The cartridge is SUPPOSED to dip into the feed ramp. That's part of how it's kept captive as the magazine starts to lose control of it. The feed ramp angle is precise. 31 degrees + 1/2 degree, minus nothing, at a prescribed depth of .400-.420 inch from the top of the frame rail

As the bullet nose dips and strikes the ramp, it's under tension...for lack of a better term...between the slide and the ramp. The magazine still has a grip, but it's gradually relinquishing that grip...and something has to take over. Nose-diving into the ramp keeps linear pressure on the cartridge between the ramp and the slide. Knock the barnacles off your thinkin' caps here.
If the round was supposed to feed in a straight line, the gun wouldn't even need a feed ramp, much less a ramp at such a precise angle and depth. Note that the ramp is also curved. That works to keep the bullet nose contained on the sides, and keeps it tracking straight. The curve and the angle literally aim the round into the chamber.

The bullet ogive is also important. The angles have to work together in order for the controlled feed to function as intended. Bullet length forward of full diameter is also important. If the cartridge is too far forward in the magazine when it hits the ramp, full control is compromised...or lost.

The corner at the top of the feed ramp also must not be altered except when correcting the feed ramp angle. If the cartridge isn't deflected upward into the barrel ramp...often mistakenly referred to as the "Barrel Throat" a steep enough angle, it strikes the barrel ramp too low.

When it does that, it pushes the barrel forward...and when the barrel moves forward too early, it also cams UP too early. This increases the angle of cartridge entry and brings about the well-known Three-Point Jam. A too-long link has the same effect, but with different mechanics.

If the round hits the barrel ramp above center, it works to keep the barrel down against the frame bed, keeping the angle correct for the horizontal break-over and chambering. Once the cartridge is horizontal, or neraly so, and deep into the chamber, the barrel is free to cam into
lockup. The noted gap between the lower edge of the barrel ramp and top corner of the frame ramp helps to insure that the cartridge will enter the barrel ramp above centerline and well forward of the corner. This is also an aid to keeping the barrel down in the bed during the initial feeding phase.

The angled approach is also a requirement for the rim to get under the extractor correctly. If the feed angle is reduced...straightened out, as some are fond of saying...the bottom corner of the extractor hook is positioned very close to the rear face of the rim. A small variation in case rim can make contact there, and cause a stoppage. Lightly radiusing the bottom corner of the extractor hook nose is done to provide a little extra clearance there...for the reason of varying case rim diameters...but it won't take care of an incorrect feed angle. The angled ramp insures that the rim approaches the hook from well underneath.

Okay...the cartridge is deflected up into the chamber. The forward radius of the bullet ogive is in contact with the roof of the chamber...but what it that cartridge is not only too short, but the ogive is also too wide. The short cartridge moves farther out of the magazine when it takes its necessary dive. That makes the dive steeper, and the resulting upward delfection is also steeper. The bullet ogive hits the chamber roof farther back and at a steeper angle...and you have another variation of the Three-Point Jam...except this one is jammed tighter. In extreme cases, this one can almost mimic the Bolt-Over Base failure to feed.

Positive magazine control of the round depends largely on spring tension. This isn't an issue when the magazine is past half-full, but as the magazine loses rounds, the tension degrades. Most important in controlling the last round...when spring loading is at a requires a helping hand to prevent the last round from moving too far forward and possibly escaping
under the inertial effects of recoil, a .45 caliber a pretty violent, slam-bang affair. That helping hand comes in the form of a tiny little bump on top of the magazine follower. Without it, the cartridge is free to roam...and often does. It may not cause a stoppage if it moves too far forward...even if it doesn't completely escape...but it feeds at a straighter angle, we've already covered...isn't good. It's not good for reliability and it;s not good for the extractor. The extractor wasn't designed to snap over the rim...not even the external extractors. The externals are simply more tolerant of the occurrence, but they'll still suffer damage if forced to do it for very long. At the least, the coil springs that drive them will
weaken much faster because they're being compressed farther than they're supposed to. Some may even compress enough to go into coil bind...which damages a coil spring quickly.

So, in summary...

The round is properly under forced, positive control from at least three points from the instant the slide hits it.
By steps:
1...Slide, magazine lips, and spring tension.
2...Slide, feed ramp, and magazine lips/tension.
3...Slide, extractor, and barrel ramp.
4... Slide, extractor, chamber roof and the top corner of the barrel ramp.
5...Slide, extractor, chamber walls, and chamber shoulder.

If the gun loses partial control of the cartridge from any one point...due to whatever is incorrect... it sacrifices a percentage of the reliability that the gun was built with.

Common wisdom has stated that the 1911 was designed to feed hardball, and any variation of that bullet shape causes problems. That's partly true, but it's not the fact that the bullet doesn't have a round nose that causes the problems. It's incorrect ogive geometry too-short overall length of the cartridge that does it.


  1. I use the CheckMate GI style mags when I shoot ball and they work very well. They are much less expensive than Wilsons, Wolffs, Ed Browns or Les Baers.

    Neither of my steel 1911s have ramped barrels but the lightweight does but all appear to work very well.

    It is a fact the the original 1911 was designed to shoot hardball but since then upgrades in both mags and feed ramps have proven that you can feed 200 grain LSWCs with the right length.

    I am uncertain as to the requirement for "controlled feeding". This was a big thing with Mauser 98 rifles but we sort of stopped that with the REM 700 push feed rifles didn't we?

    The current wisdom is the use of CMC tubes with the Tripp Cobra 7 round conversion. I am tired of chasing the latest fashion in 1911 accessories myself but you guys just carry on.

  2. Good lord! I cannot comment... I may be burned at the stake!!!!

    Andy >;)