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Discussion Starter #1
Fellows. New guy here. Have one of many questions I'll be asking.

As for the Firing Pin Stop. I "assumed" its purpose is to retain the Firing Pin in the Slide.

I've read/seen about its sharp bottom corner being radius somewhat.

I've read about the "results" of doing this modification but exactly how does radiuusing this corner of the FPS accomplishish these "results". Does it allow the slide to travel rearward during recoil easier? Does the FPS with a 90* corner (instead of a radius corner) "dig into" the frame? I'm having a time understanding the "operational" effect of this mod.
Thanks,
ptf18
 

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CEO of DILLIGAF industries
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The bottom edge of the firing pin stop is what pushes the hammer back . A radiused bottom has less friction against the hammer . A lot of 1911s already have the radius . I recommend Patrick Sweeney's or similar book on gunsmithing the 1911 .
 

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1911 Pistol Smith
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The purpose is to slow down or speed up the cycling process depending on recoil spring and main spring used. It can reduce felt recoil, but changing the actual timing of the gun. Radius on the FPS which was not the original design btw, will allow the use of lighter recoil and main spring, in turn speeding up the cycling process. If the slide moves too fast it can cause feeding and ejection issues.. If spring too heavy can cause short cycling of the slide. The 1911 is a fine piece of machinery lol..

I am a personally a proponent of the flat FPS or a very slight radius as it allows the pistol time to do what it needs to do during the cycle of the gun.. I.E. in short to allow the ejection of the spent case as well as the stripping of the next round of the magazine to inject into the chamber of the barrel. Also when fit properly it keeps the extractor in a constant position to prevent clocking or rotation of the extractor allowing it to change the hook relationship to the rim of the case. I don't see this as a huge problem often as it has to be pretty bad to cause problems.

The FPS doesn't dig into the frame it contacts the hammer cocking it into position to fire during cycling..

hope this helps some. There are many more in here with much more experience and knowledge concerning this and I'm sure they could add or maybe give some other relevant information.
 

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Fellows. New guy here. Have one of many questions I'll be asking.

As for the Firing Pin Stop. I "assumed" its purpose is to retain the Firing Pin in the Slide.

I've read/seen about its sharp bottom corner being radius somewhat.

I've read about the "results" of doing this modification but exactly how does radiuusing this corner of the FPS accomplishish these "results". Does it allow the slide to travel rearward during recoil easier? Does the FPS with a 90* corner (instead of a radius corner) "dig into" the frame? I'm having a time understanding the "operational" effect of this mod.
Thanks,
ptf18
First of all... WELCOME to the forum. Secondly, Its good that you have questions because this place is full of answers... some of them even good answers. :D:D
 

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The Tinker
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Fellows. New guy here. Have one of many questions I'll be asking.

As for the Firing Pin Stop. I "assumed" its purpose is to retain the Firing Pin in the Slide.

I've read/seen about its sharp bottom corner being radius somewhat.

I've read about the "results" of doing this modification but exactly how does radiuusing this corner of the FPS accomplishish these "results". Does it allow the slide to travel rearward during recoil easier? Does the FPS with a 90* corner (instead of a radius corner) "dig into" the frame? I'm having a time understanding the "operational" effect of this mod.
Thanks,
ptf18
The reduction of the radius on the FPS decreases the mechanical leverage the slide/FPS puts on the hammer. Less mechanical advantage means more energy is required to overcome the resistance of the hammer and allow the slide to travel rearward. Because more energy is required to get things moving, the time it takes for the slide to overcome this resistance (or said simply, to cock the hammer) increases, allowing a bit more time for the bullet to travel down the barrel and reduce available gas pressure.

Increased time and reduced pressure means the rearward velocity of the slide is reduced. Less recoil spring is required to control a slower slide. And the slide impacting the frame at a slower velocity affects felt recoil, if only a little.

I don' t profess to understand every little detail of this, but I use the size of the radius on the FPS to help with 'timing' the pistol for a specific user and/or load.
 

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The reduction of the radius on the FPS decreases the mechanical leverage the slide/FPS puts on the hammer. Less mechanical advantage means more energy is required to overcome the resistance of the hammer and allow the slide to travel rearward. Because more energy is required to get things moving, the time it takes for the slide to overcome this resistance (or said simply, to cock the hammer) increases, allowing a bit more time for the bullet to travel down the barrel and reduce available gas pressure.

Increased time and reduced pressure means the rearward velocity of the slide is reduced. Less recoil spring is required to control a slower slide. And the slide impacting the frame at a slower velocity affects felt recoil, if only a little.

I don' t profess to understand every little detail of this, but I use the size of the radius on the FPS to help with 'timing' the pistol for a specific user and/or load.
Helllllllp Mister Wizard!!!!
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It’s been explained much better than I ever could already on this thread. All I know is it was an extremely effective and inexpensive modification to my colt delta and Dan Wesson Bruin 10mm’s. Especially the delta, it stopped the case from being tossed into next week, reduced recoil and potential frame battering and there was no need to try and over spring the factory recoil spring set up that I see a lot of delta owners doing.
 

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Discussion Starter #11
Fellows. Thank you all for the "education". Good to get a understanding on what the heck is going on with a 1911 and how it effects "things"... all sorts of things.

Had my Rock Island MS out to the range today. I'll post another different question about that.

Once I returned home and dissembled the gun for cleaning I understand how a "wiggling" (loose) FPS can allow the extractor to rotate... not very much (at least on mine)... but enough to allow it to "pull" on a fired case in a "different" location than the previous fired case. Hard to believe that "different" location( of the extractor onto the case rim) would/could case the fired case to be flung out of the gun and into a different location than the previous fired case.

I did some "out in open' (from my holster & away from a bench) and found a pile of cases in about the 2 oclock (from me) location. But there were a few that were behind me (5 oclockish).

Does this mean anything? Perhaps its the shooter?
 

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Hard to believe that "different" location( of the extractor onto the case rim) would/could case the fired case to be flung out of the gun and into a different location than the previous fired case.
Once you correctly fit an oversized flat bottom firing pin stop (EGW or Harrison) the clocking of the extractor will stop. Then you can go test fire the pistol to see if the brass is still flying all over the place. If it is, before you clean the pistol you should carefully examine the area around the ejection port for brass smears. Take note of the position of the smears (inside the slide below the ejection port, front edge of the port, etc). This will provide clues on how to proceed to fix the errant ejection.

As a general rule, the more tension there is on the extractor the more consistent the ejection pattern. However, feeding should not be compromised by having too much tension on the extractor.

Read more about extractor tuning HERE.
 
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