I've noticed on a more expensive 1911 I have(an Ed Brown) that the lower bottom edge of the breechface is slightly beveled/radiused at almost the same degree that the firing pin stop is radiused at its bottom edge. I think the same thing is true of my STI Trojan. I also have an SA-GI that has a sharper edge at the bottom of the breechface. Any advantage in timing or smoothness to making the lower breechface edge on the SA-GI look like the way that the Brown has been shaped? The Trojan and EB slides definitely hand cycle much more smoothly than the SA-GI. Of course, I realize that other factors are at work in the differences also. Thanks in advance
How about for reducing the violence to the disconnecter?
Yes. That's part of my thinking also. Thank you.
Another reason for breaking the sharpness of the bottom corner of the the breechface would be to provide a smooth edge for the base of the cartridge being fed to slide along after it's released by the magazine and stuffed up along the breech face by the next cartridge (or the magazine follower).
Before tinkering with it, however, make sure you know what the specification for this corner is. If it's got sharp edges, I'd recommend just breaking them with a fine abrasive file (stone). This is no place for a standard file without knowing what this corner's supposed to look like - consider the consequences of filing off TOO much!
A search of my fuzzy Springfield Armory and Rock Island Arsenal blueprints with my equally fuzzy eyesight couldn't locate any specification for this corner. Perhaps some forum member with clearer blueprints and/or vision can let you know what it is.
And, if the gun works, well . . . . why fiddle with it at all?
niemi, thanks. Tinkerers have a hard time leaving well-enough alone, if it ain't broke don't fix it etc. But like Tuner says - sometimes it's the little things that get ya.
All 1911's should have the beveled edge... also helps to polish it a bit as well.
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All 1911's should have the beveled edge... also helps to polish it a bit as
well.
Hmmm - I've always had a problem with "should" (eg, you "should respect your elders) If you say it, then i might assume that it is in the JMB bible of drawings.
HOWEVER - if I remember the question noted that there were 1911s with and without... and WHY?
My prints don't seem to show this. What is the specified radius?
well - I already touched one before I answered... just to be sure that the memory was ok.
I'm confident that you shall have been right at least 1/2 dz. times before the 1st. (I'll touch)
I couldn't find any specs in the prints I have either. I have read that this corner (not beveled at the time of the incident) on another make of pistol was determined to be the cause of an out of battery firing while trying to clear a jammed round or the slide slamming on a loose round. So the corner was beveled to prevent it from setting off the primer. I don't remember all the details. I can tell you that I personally have seen this situation, corner of a slide that had the bevel in contact with a primer, and that I was extremely careful clearing this jam.
As long as it's not sharp... it SHOULD be rounded a bit.
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As long as it's not sharp... it SHOULD be rounded a bit.
Not specified as a dimension, but it needs to be there. No need to overdo it.
Just lightly break the corner at 45 degrees. It's another redundant feature that reduces the odds of a misfeed. By the time the round starts to ascend the feed ramp, the case rim will be angled away from the corner, and by the time the round has broken over to horizontal, a sharp corner would have little opportunity to grab the rim... but the bevel is added insurance, and... as Iron Bottom observed... it can light off the primer under certain circumstances.
Again... Overdoing it isn't necessary, and it can allow the slide to ride right over the rim if the tolerances stack in the wrong direction.
Tuner, thanks. Since I first posted this thread, I have looked at the bevel on the STI Trojan. It is at about 45 degrees and more pronounced than the bevel on the EB. I think I'm going to add this bevel to the SA-GI slide. But advice given by yourself and others is well-taken. Easy does it.