EGW FPS works in my OM

[DanM]

After watching 1911 Tuner install install one in my 1911, I deceided to try it myself. I installed one in my Para12LDA with no problems. I do admit the fit is looser than John's work, but I think it is working, and here is why:
With the new EGW FPS in place, I ran some mild loads thru the pistol, and it had 3-4 failures to return to battery per mag. Tried some warmer loads, and still had the same problem. A whack on the rear of the slide closed things up every time, but a new FTF problem I did not need. I soon remembered that John had also installed a stock recoil spring with the new FPS in the 1911, and that a Wolff EP spring still resided in the OM. Well I came up with a factory OM recoil spring and put it in the Para12. Problem solved! I think the square cut EGW FPS was slowing the slide speed enough to cause the failures to return to battery with the EP recoil spring. The pistol runs like a train now....

[Dave Berryhill]

The FPS shouldn't affect the slide returning to battery (unless it is protruding below the level of the slide). When the slide has moved all the way to the rear the FPS is out of the equation and it's the recoil spring doing the work, as you found when you replaced the spring with a fresh one. You may also need to check the tension of your extractor. The extractor tension that was set with your old (loose) FPS may be too much now.

[DanM]

So you don't think the square cut FPS slows the slide? How do you explain the softer spring fixing the problem? I am not sure the slide was making it all the way to the rear with the EP spring. It is running great now with the OEM spring back in and the new EGW stop installed.

[tightgroups]

The old firing pin stop probably had a radiused bottom edge. The EGW is square, isn't it? If it is then it would make a little difference and slow the slide down on the return to battery. Wasn't it designed this way for that reason?

[1911Tuner]

The FPS didn't slow the return to battery. As Dave noted...once the hammer is cocked, the stop doesn't haveany effect. The heavier spring used with the stop likely caused short-cycling.

[Dave Berryhill]

So you don't think the square cut FPS slows the slide?

I didn't say that. I said that the FPS doesn't slow the slide when it's returning to battery (moving forward). When the slide reaches the rear of it's travel, whether it's moving fast or slow, it reverses direction and moves forward. The forward movement is all recoil spring. Now if the slide doesn't make it all the way to the rear because of the FPS (or any other reason) then that's a different story.

[tightgroups]

Hmmm...boy am I an idiot! (please, no eager nods of agreement) I had heard stories of the original FPS being square and making it harder to rack the slide. The Army had asked JMB to change it, thus the radiused FPS. Is this inaccurate information?

Thanks.

[DanM]

OK, thanks guys. Maybe I was right for the wrong reason. I do think it was short cycling because of the heavy spring combined with the new FPS. At any rate, it runs great now. So, I take this to mean that the new gadget is working even if I can't feel the difference in recoil. Maybe I am shooting too many magnums to notice the difference in a lil' .45....

[Dave Berryhill]

The original FPS wasn't square but it did have a smaller radius on the bottom edge than the current version. It did make it harder to pull the slide to the rear when the hammer was down. Moe designed it that way for the function of the pistol not for the convenience of the shooter.

The EGW firing pin stop comes with a square bottom edge to allow you to put your own radius on it. It's not meant to be left square.

[OD*]

The Army had asked JMB to change it, thus the radiused FPS. Is this inaccurate information?

Thanks.
The Ordnance Department actually asked Colt for the change, once JMB relinquished a patent to a manufacturer, he was done with it for the most part.

http://i206.photobucket.com/albums/bb274/OD1911/FPS2.jpg

[gbw]

So you don't think the square cut FPS slows the slide? How do you explain the softer spring fixing the problem? I am not sure the slide was making it all the way to the rear with the EP spring. It is running great now with the OEM spring back in and the new EGW stop installed.

The square cut FPS retards the beginning of slide movement a bit.

I've seen 1911Tuner say many times over the past many months:

"...don't overspring the gun."

It finally dawned (I hope!) - things must have time to do their doins' on the feed stroke. A stronger spring increases the violence and reduces the time, both detrimental I believe. If it was short stroking because of the EP spring that would also cause problems, though I do wonder how likely that is.

[tightgroups]

Cool information and a great little pic to go along with it! Thanks.

[BigJon]

The Ordnance Department actually asked Colt for the change, once JMB relinquished a patent to a manufacturer, he was done with it for the most part.

http://i206.photobucket.com/albums/bb274/OD1911/FPS2.jpg

Thanks for posting this. I really appreciate it when someone posts an official document related to an issue.

Best,
Jon

[OD*]

You're welcome, Jon.

The picture come from one of Charles Clawson's books on the M1911 & M1911A1.

[1911Tuner]

I first noticed the small-radius firing pin stop...and its effects on the cycling of the slide...sometime around 1968, when I was handling and firing a 1916 Colt Commercial Government Model that my father and I had rebuilt. The stops were hard to come by, even in those days...because most of the GI pistols had been retrofitted with the new stops. Probably the only ones to escape were the ones that had been "liberated' by military personnel. We could occasionally find one or two in small parts boxes at gun shows...so I was forced to make my own. EGW's understanding of its effects, and subsequent marketing of the square-bottomed stops have been a godsend.

[tightgroups]

Why, exactly, have they been such a God-send Tuner? I really want to understand what and why this often understated part is so important. I don't doubt it, I just want to have a better understanding of it as it relates to other parts in the aggregte.

Thanks.

[1911Tuner]

Why, exactly, have they been such a God-send?

Because when I need one, I can order it from Brownells instead of havin' to make the flippin' thing... :D

The effect that it has is delaying the slide at the instant that it starts to move by reducing the slide's mechanical advantage in cocking the hammer. That, in turn, keeps the slide's rearward speed and energy lower, and reduces the impact at the other end...which reduces the amount of felt recoil generated by the slide smackin' the frame.

[tightgroups]

Ahhh...I was slightly confused earlier. Thanks for clearing it up for me. I hear they're also a big help in stopping/preventing the extractor from clocking, if installed correctly. I guess it's easy to take too much material off while fitting and ruining the advantage of it being oversized. Tuner, if you had to pick only three files to own for pistol smithing, which ones would you choose?

[OD*]

I hear they're also a big help in stopping/preventing the extractor from clocking, if installed correctly.
True, but any over-sized fitted FPS will accomplish that task. ;)

[gbw]

Because when I need one, I can order it from Brownells instead of havin' to make the flippin' thing... :D

The effect that it has is delaying the slide at the instant that it starts to move by reducing the slide's mechanical advantage in cocking the hammer. That, in turn, keeps the slide's rearward speed and energy lower, and reduces the impact at the other end...which reduces the amount of felt recoil generated by the slide smackin' the frame.


The initial movement is delayed slightly, no doubt. For the lower slide energy and speed?

Well....it sounds right intuitively. But I wonder. The shorter moment arm does increase the force required to move the hammer. But it also gets the hammer out of the way faster i.e. the hammer slows the slide for a shorter part of the cycle. I think you're right, but I've not done the mechanics and I'm not sure. Perhaps when one of the physicists has some time he'll take a stab.

Think of pushing against a restraining rope across a doorway. The rope stretchs a little (hammer cocking), then breaks (cocked). For a larger rope (square stop), the acceleration will begin later while we increase our pushing. But it will be faster when the rope does break - and maybe we end up on our nose! For a weaker rope, acceleration begins earlier, but it will be slower and resistance will last longer. In both cases it takes the same amount of work to cock the hammer.

Or, I recall the old jet dragsters. They locked the brakes, lit the afterburner (THAT was something to see), allowed max thrust to build, then tripped the brakes. What a show. Before they learned to hold the brakes at the line the things were pretty anemic.

[Dave Berryhill]

...if you had to pick only three files to own for pistol smithing, which ones would you choose?

It's tough to narrow it down to three but I could probably get by with an 8" mill b@stard, an 8" second cut and either a 6 inch standard pillar file #2 cut (Brownells #191-399-110), a 6 inch smooth or a 6 inch 2nd cut file (American Pattern). You can buy the American pattern files at a hardware store or Home Depot if they have them. Get good quality files such as Nicholson (made in the USA or Europe, not China) if you buy them at the hardware store. Also get a file card or file cleaning brush and clean them often. You'll feel the difference and get a better finish when your file is clean vs. loaded.

To supplement those, the little 4" swiss pattern #2 cut file from Brownells is really handy and a set of fine cut needle files would be next. Then I'd get some specialty files like a dovetail file, checkering files, one for 1911 barrel locking lugs..........

[tightgroups]

Thanks Dave, exactly what I was looking for, appreciate the response. I've got some needle files (china) that are worth about what I paid, almost nothing, but better than shooting a blank.

[1911Tuner]

Your file is your friend. Become one with your file.

And use a little chalk on'em. ;)

gbw...A misconception concerning the cocking of the hammer is that it happens smoothly...with the hammer remaining in contact with the slide. It doesn't. It's slammed backward and bounces off the grip safety...and stopped by the slide. Look on the underside of the center rail, right at the rear. You'll probably notice some peening right at the rear edge of the rail at the firing pin stop.

[tightgroups]

Kinda violent, huh? Goes with the territory. You forgot to "grasshopper" to that statement Tuner.