John Travis Posted July 17, 2006 Share Posted July 17, 2006 Well...This may get a little involved, so I've started another thread on it. As hard as it is to draw a picture with words, I'll give it a shot because some have expressed a genuine interest in this. Morph yourself down to a millimeter tall, and use your mind to "see" the events in slow-motion, one step at a time. The slide moves forward and strikes a very small "chord" at the top of the case rim, causing the cartridge to nose down into the feed ramp. Much hand-wringing has been made of this "nose-dive' but it's a necessary function in the controlled feed design because it works to keep the case rim in firm contact with the breechface. The slight rearward rake of the breechface helps nose the round downward. The cartridge then tries to take an abrupt 31-degree upward turn, and the rake again comes into play to make that turn more gradual. If the breechface was set too close to perpendicular, the bullet nose would literally bounce off the feed ramp, and nose up at a steeper angle, possibly causing a bolt-over base malfunction...or at the very least, hang the bullet nose at the roof of the chamber hood. At this point, extractor pickup hasn't begun. A word on extractors before proceeding: The practice of radiusing the bottom corner of the extractor claw to prevent the rear bottom corner form contacting the forward face of the inner case rim is most often overdone, with the radius far too heavy. This does work to facilitate the breakover, but also delays extractor pickup, increasing the possibility of the round being chambered ahead of the extractor. It's therefore recommended that the radius be held to a minimum. And...A word on magazines: The old, tapered lip design...aka "Hardball Magazine" worked in conjunction with the angled breechface to effect a more gradual release...and gradual is where it's at. The more recent, parallel lips and "timed" release designs tend to release the round too early and too abruptly. The tapered lips start the release earlier and finish it later, while the parallel lips keep the round from releasing until the last moment...which makes the correct angle on the breechface all the more critical. Necessary for cartridges with a short OAL, this design works against a gradual release for longer rounds. Other issues will have an effect on the actual release point of the magazines with tapered lips...variations in the actual angle and distance between any given point, along with variations in case rim diameter...but as long as the release is gradual, it works out. Okay! Back to the video. As the cartridge moves forward on the 31-degree angle, the bullet nose makes contact with the underside of the chamber roof, which forces it to begin the horizontal breakover. The extractor has picked up the rim, and the side of the case is starting to pivot on the floor of the chamber...and the round is entering a condition of stem bind...which is also necessary for full control to be maintained...but beyond a certain point, the stem bind can become a three-point jam. If the angle on the breechface is TOO far removed from perpendicular, a TPJ is almost a certainty, though other issues can contribute to the malfunction. So...The round needs a little extra help in breaking over...and the rearward rake of the breechface again comes into play. The rim is almost in correct position on the breechface, but there's still a little friction between the bullet ogive and the chamber roof. The slide is pushing the round forward, with most of the push coming at the top of the rim with the bottom not in contact...and the angle forces the round to nose down very slightly, breaking much of the friction with the top of the chamber. The barrel hood is in full contact with the slide, and beginning its ascent into battery. Here, if the breechface is too close to perpendicular, the round continues to be shoved in a straight line relative to the breechface, and this friction remains constant. The barrel rises too early, and contacts against the underside of the slide lugs...and working in conjunction with the bullet-to-chamber roof contact...you have the potential for a failure to return to full battery...just slightly out....with light thumb pressure placing it in. Again...other factors may contribute to the malfunction...such as an over-tensioned extractor, etc... and should be eliminated before looking to the breechface specs. Understand that this is for educational purposes only, and altering a breechface without the proper equipment and the necessary skillsto use that equipment is ill-advised. Polishing a breechface with sandpaper should be done carefully, with no attempt at making it like a mirror. Toolmarks should be lightly burnished. Attempting to completely remove these "swirls" gives us about a 50/50 chance of doing expensive damage...and most especially a file should never be used for this. The chances of maintaining the side-to-side squareness of the face AND the correct angle is practically nil. It's been said that the 1911 was designed to function with hardball, and unless radically altered and used with timed-release magazines, will only function WITH hardball...but I beg to differ. If the breechface angle is within spec, and the pistol in good overall condition, it will feed and function perfectly with hollowpoints and even lead 200-grain H&G SWCs fron the old "Hardball Only" magazines. I have several original, unaltered USGI pistols...1911 and 1911A1...that will shoot that bit of wisdom down, and any who are within driving distance are invited to come see Black Army Colts and Remington Rands gobble the stuff like they were specifically tuned for it. Come see/Come say! Link to comment Share on other sites More sharing options...
Vlad Posted July 17, 2006 Share Posted July 17, 2006 Now that we have three different threads on this issue for some reason, I'll ask my question again. Hopefully I'll get an answer: IIf the breach face is at 90, all other things being equal, will the firearm function? Will any parts wear out sooner, and will that wear create a problem for the gun before other parts fail of natural wear? Link to comment Share on other sites More sharing options...
John Travis Posted July 17, 2006 Author Share Posted July 17, 2006 (edited) Will it function? Probably...at least in most cases/most of the time. Depends on several things. Will the function be optimum? Probably not. If you reload, you may have noticed distinct dings on the edges of some of your cases that eventually make it hard to fit the rim into your shell holder. There's a sign of a push-feed and extractor hook snapover. The gun may run well for a time, and suddenly the extractor loses tension...or breaks in some cases. If you have intermittent failures to go to battery that defy all reason and attempts to correct...that's another sign. It may not occur frequently enough to cause concern on a range gun, but may be just often enough to undermine your confidence in a carry gun. Ever heard of or known personally of very old pistols that are much worse for the wear that still function perfectly...even with 50...60...70-year-old...or older extractors? There's a sign that the breechface is perfectly within spec...or as perfect as a dimension can be, since there's really no such thing as a perfect dimension. Ever seen a stock USGI pistol that'll feed everything that ya throw at it just as well as hardball? There's another sign. If the gun is all within spec, and in good condition...not worn out or rattle like a bucket of rocks...it'll match or outrun any Glock, Sig, USP, or anything else out there, reliability-wise. Boring reliability. Gaston Glock knew about it, and addressed the issue by targeting the areas of potential problems by rolling the barrel ramp/throat into the floor of the chamber and reducing the angle of entry...but he also destroyed much of the case head support too...Same with the USPs that I've seen. He used an external, spring-loaded extractor with nose geometry that would tolerate an occasional snapover...but he also lost the advantages of positive controlled feed on every round, every time. In short...A trade-off that worked well enough to put the guns into production. Is the angle that critical to function? Maybe not in a given gun, since other things are also at work. Tolerance stacks sometimes bring things into harmony...or completely out. Depends on the particular gun in question. Overall, as applied to a million guns with a requirement for parts interchangeability between several different contractors? Yes. The Government requirement for the five WW2 contractors was to be able to disassemble one gun from each...toss the parts in a box...shake the box...and assemble five working pistols from the jumble...and it worked, time after time after time. And it had to be the same for any spare parts supplied by any of the contractors. Again...these points were never meant to fuel a flame war, or deride any smith's approach to building a gun. It began in an attempt to keep wsimp from making his problem worse with a file...and later purely for educational purposes meant for those who want to understand how the gun functions. Sorry if I ruffled any feathers. Edited July 17, 2006 by John Travis Link to comment Share on other sites More sharing options...
Wild Bill Caldwell Posted July 17, 2006 Share Posted July 17, 2006 Shred and Harmon ...On another thread brought STI and Dave Dawson into this discussion. I'm shootin' a pistol I built on a STI frame , Caspian slide.. Possibly StI's work because the mags hold the loaded rounds higher.....I've built my share of Hi Cap pistols and I do beleive the mags are different....But...At this point, in this place in time... HELL....I ain't sure I know COME 'ERE from SIC 'EM.... Thanks , Wild Bill Link to comment Share on other sites More sharing options...
Vlad Posted July 17, 2006 Share Posted July 17, 2006 Well if my trigonometry is not failing me, one side of the breach would be 0.01 inches away from the 90 degree line. I've used a bit of rough numbers to come up with that so it might be .009 or .012 but 0.01 is nice simple. The rim of the .45acp is nominaly .049, so about 5 times larger. I'm no expert, but I've seen .45 cases with a lot more rim that that, and some shot so many times to be worn out to the point that the head stamp is no longer readable. Further, leaving aside that the fact that there must be some brand to brand variation in case length as well, almost no one trims their pistol brass when reloading, and .45 cases last until you lose them, so there must be some case lengthening going on. The .45 ACP still headspaces on the case mouth last I checked, and given the variations in brass size, rim size, etc, I just don't see how the .01 difference on the breach face can be called critical. Would it help if it was there? I'm conviced it would make feeding smoother. But so does cleaning my gun. My Springfield Milspec gets cleaned about every 1000 rounds, or when I can't stand the sight of it anymore. I get enough powder residue buildup on the feed ramp to make .01 inches uninteresting when it comes to feeding geometry. I don't doubt that the angle we are taking about would make feeding feel a touch smoother, or make the gun more forgiving of other faults, but absent other faults, I'm not convinced that those 52" can be called critical. Nice, usefull, craftsmanship, I'll give you all of those. But then again, I'm not a gunsmith. I just try to wear the things out. Link to comment Share on other sites More sharing options...
Wild Bill Caldwell Posted July 17, 2006 Share Posted July 17, 2006 VLAD, I,m guessin' You just added fuel to the fire by statein'... possibly ..4 or more reasons why 1911's sometimes headspace on the case mouth and more often times headspace on the extractor. In dealin'with more "things'" Than just 1911's.....weak or slow extraction can cause a lot of problems. Thanks Wild Bill Link to comment Share on other sites More sharing options...
EricW Posted July 17, 2006 Share Posted July 17, 2006 If we stop responding to these threads, eventually they will get tired of talking to themselves and go away... Link to comment Share on other sites More sharing options...
rubberneck Posted July 17, 2006 Share Posted July 17, 2006 Eric, while their delivery might need some work, I find it troubling that a dealer mod on this board is expressing an interest in running off two posters simply because you don't like their style. Link to comment Share on other sites More sharing options...
EricW Posted July 17, 2006 Share Posted July 17, 2006 (edited) I'm not trying to run them off, but the only reason these guys are here is to be abrasive, combative, and abusive to some people that I do business with and greatly respect. The manner in which Mr. Travis publicly belittled Benny Hill is totally inexcusable. I couldn't give a rat's ass as to what the breechface angle on my race gun is. All I need to know is that if Benny builds me a gun, it's going to run. Edited July 17, 2006 by EricW Link to comment Share on other sites More sharing options...
smokshwn Posted July 17, 2006 Share Posted July 17, 2006 Rubberneck, I am with Eric. There are elements of "style" that differ within all of us but many times both posters clearly traveled the road of condescension. In my opinion, regardless of the knowledge you may think you have, this never helps you get your message across and seriously compromises your credibility. Condescension always indicates insecurity about yourself or your subject and that rarely happens with those who are truly knowledgeable. Take care, Craig Link to comment Share on other sites More sharing options...
tightloop Posted July 17, 2006 Share Posted July 17, 2006 +1 Eric Link to comment Share on other sites More sharing options...
Flexmoney Posted July 17, 2006 Share Posted July 17, 2006 We are done seeing the bickering folks. The little snipes aren't acceptable here on this forum...no matter who they come from. Mr. Travis and Wild Bill..welcome to the forum (truly). I've enjoyed reading your posts on other forums. It seems we got off to a bad start. Which, can happen to good people. Some of our regulars got a bit defensive with somebody they didn't know...posting a strong attitude. I think we are all big enough people to figure out how to get along. (But, if there is going to be a get-together where everybody whips them out and sees who can piss the farthest...let me know, I always like to win a bet. ) I am closing this thread (and the others), as we've taken this about as far as we need to. Kyle F. Forum Administrator Link to comment Share on other sites More sharing options...
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