1911 Premature slide lock: replacement slidestop?


Chuck Dye
May 29, 2004, 04:40 PM
The Springfield Armory parkerized 1911-A1 is locking prematurely when loaded with 230 grain ball, two to three times in fifty rounds. The top round on lockup has a nice bright scar from the slide stop and the stop itself has a fine telltale of copper even though the problem cannot be duplicated with the gun unsprung and hand cycled (with firing pin removed.) The answer is obviously to trim the slide stop. Given my history with such things (cut that 2x4 three times and it is still too short!) I want a replacement available before I start. Any suggestions on choosing a replacement that will not also need trimming would be welcome.

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May 29, 2004, 06:48 PM
Howdy Huck,

Since you specified that you don't want to file on your stop, try a
McCormick slidestop. It's MIM...just like the one you've got...but I've
got a couple of those in hard-duty range beaters that have seen several
thousand rounds without a problem. I haven't had one touch the rounds in the magazine and do a premature slidelock, either...Understand that
this is no guarantee that it will do likewise in your gun. It may be a matter of a tolerance stack-up on the location of the slidestop hole in your frame, and light filing may be the only recourse.

The McCormick stops are about 20 bucks retail in Brownells. Pretty good
slidestops, and if you decide to try your hand at fitting one, you're not
out a lotta hard green if you kill it. FWIW, a smith could do the job in 10 minutes for about the price of the McCormick stop...or less.



Chuck Dye
May 29, 2004, 08:34 PM
Thanks, ‘Tuner, I do intend to take a file or stone to the one I have, but hard experience suggests I at least research a replacement. *sigh* On the other hand, my local smith is generous with his unpaid time and I could do worse than to give him the work.

With regard to metal injection molding, the pistol is 11 years old. I have had the idea MIM arrived on the scene more recently. Am I wrong?

May 29, 2004, 09:23 PM
With regard to metal injection molding, the pistol is 11 years old. I have had the idea MIM arrived on the scene more recently. Am I wrong?

Probably investment casting if it's that old. Look for a lengthwise parting line on the underside of the arm. If the line isn't there, it could be barstock,
but I've seen MIM sears in early 1991A1 Colts...so it has been around long enough to be there. MIM will have a sprue mark..On a slidestop it will be round or square. No lines or odd geometric shapes on the back of the arm, and it's likely machined barstock.

One other thought...If you're running a shock buff, take it out and try it.
I've seen some pistols do a premature lock with a buff in, but clear up when the buff is out...and nobody seems to know why except the gun.

Wilson bulletproof slidestops have a shelf for the plunger to bear against that prevents premature lock...but they usually need a little work in order to get the slide to lock on empty.

Since the pistol is that old, it's also possible that the plunger spring is worn out. A new one might fix the problem. The bullet ogive contacting the
lug isn't the only thing that'll cause it...Inertial bounce during recoil will do it too, and more often happens when a heavy, extended stop is used, or the plunger spring is tired. Check the end of the plunger also...it might be worn flat.

Chuck Dye
May 30, 2004, 12:22 AM

Again, thank you. In no particular order:

The original stop is, by your description, cast.

The round count on the pistol is unknown, probably between 750 and 1,500. The plunger has barely lost its finish and it takes some effort to seat the stop on reassembly, so I think the plunger and plunger spring may be ruled out.

On the recommendation of my smith, I am running a CP Bullets SUPER TUFF™ buffer. Not just a buffer, but the thickest I have seen. I will pull it for some tests in the morning. (My back porch range is flood lit and the neighbors’ ears protected by distance and forest, but it seems best not to shoot after sundown. :))

My first inclination towards trimming the stop is to stone off the copper washed portion, shoot, and repeat until the gun runs reliably. The hope is that after I eliminate the premature lock up, I will still get reliable slide lock as the last round ejects. The question I hope you can answer is: should I stone parallel to the both the bore axis and the grip axis, creating a flat, or must I stone the faces of the pyramid (equally? unequally?) to maintain that shape without a flat? This, of course, assuming that pulling the shock buff doesn’t resolve the issue.

And we thank you for your support,

May 30, 2004, 10:49 AM
Or file it with a flat needle file. Just follow the angle where the contact point is...Go slow.

My bet is on the shock buffer...Standin' by for the test report,

Tuner the Gambler

May 30, 2004, 07:12 PM
Hmm, coulda swore I replied to this last night, but here's my take:

I had this same problem with my Kimber Compact CDP I. I got a new slide stop from Kimber and it didn't help. Took it to a gunsmith who fixed in about 30 seconds with a grinder, and said he's seen this before. I'd just take it to someone and let them do it - it cost me $10.

Dave Sample
May 30, 2004, 09:16 PM
Ed Brown slide stop would be my choice. I also like Tuner's CMC selection. The big clue is to take away the metal where the mark is. This is a common problem with the parts we use today. Most of them are not even "drop in's" at the factory.

Chuck Dye
May 30, 2004, 09:38 PM

Thanks, you did reply, on the 1911Forum.com. I posted here, 1911Forum, and The Firing Line to catch input from those rare birds who do not frequent all three.

A wet day has kept me from testing-my porch range does not yet have an awning- but I have reached some conclusions, anyway:

1911Tuner’s remarks about the buffer led me to realize that the change from a thinner buffer coincided with the emergence of the slide lock problem. The TUFF BUFF™ is so thick that the slide cannot be released slingshot fashion, the slide release is required. 'Tuner's suggestion (http://www.thehighroad.org/showthread.php?s=&threadid=59533) on the use of a modified spring guide looks like a reasonable way to have both reliable slide lock and a stout buffer. Worth the experiment, anyway.

I have also decided to have my smith touch up the slide stop (I definitely am over due to spend some money with him, given the help he has provided free): the copper wash is proof that bullets are hitting the stop. Merely changing the buffer will not cure that.

I like chicken soup solutions (they couldn't hurt!) at least as first efforts.

Chuck Dye
June 1, 2004, 02:13 AM

Only had time and resources for 75 rounds without the buffer. Nary a bobble or hitch. Still plan to trim the stop, or have it trimmed. Many thanks.

In your Quick Fixes thread, you describe thinning the flange of a full length guide rod to make additional room for a buffer. Does that not also apply to the original shorty?


June 1, 2004, 06:58 AM
You said:

Nary a bobble or hitch.

Yep...Sometimes it's the little things that getcha.;)

Tuner's Dictum:

"It's usually somethin' simple."



Still plan to trim the stop, or have it trimmed.

Uh...Gunsmith's Cardinal Rule:

"If it's runnin', don't keep fixin' it 'til it's broke." Or...as a certain
songwriter put it:

"You gotta know when to hold'em...know when to fold'em...know when to
walk away, and know when to run..."

Yes. You can thin the head on the standard guide rod, but it may not keep the slide from locking prematurely. I do that modification mainly on pistols
that have reduced slide travel to start with, (Commanders) and the owner wants to run a buff for heavy range duty. The premature slidelock issue doesn't seem to be related to slide travel, and if a buff causes the problem with a standard head, it will usually do it with a modified head too.



Old Fuff
June 1, 2004, 10:03 AM
1. Field-strip the pistol.

2. Repalce the slide stop in the frame.

3. Load a magazine with the ammunition you usually use when the problem occurs.

4. Insert magazine into frame.

5. While holding the slide stop against the frame, push the cartridges out of the magazine with your thumb.

6. Use eyeballs to see if the slide stop's lug is touching the bullets. Use new-found knowledge to make corrections.

June 1, 2004, 08:30 PM
Thanks, you did reply, on the 1911Forum.com.

Ah great, now I can't keep track of where I'm posting! :p

June 2, 2004, 03:28 AM
Valkman said:

Ah great, now I can't keep track of where I'm posting!

ROFL...I am SO glad to know that I ain't the only one that happens to...:D
Ever get PMs crossed up too? :rolleyes:

Tuner the Confused...at times

Chuck Dye
June 12, 2004, 12:54 PM
Possible mechanism…

Fooling with the buffer I removed from the pistol, I noticed that it has swollen a few thoudandths of an inch, so I put a fresh one in the gun and ran a box of ball down range. I know the sample size is inadequate, but there were no premature slide locks.

According to the blurb in Brownell’s online catalogue, the CP Bullets SUPER TUFF™ buffer is made of nylon. Nylon is notoriously hygroscopic and swells as it hydrates. Discovering the swelling and remembering how hygroscopic nylon is caused my memory to go through a great deal of clanking, grinding, moaning, growling, and the like, and cough up a another detail: the premature slidelock did not begin precisely with the use of the CP BUFFS™, it began some time after the 1911 became the out & about gun. I think that the difference was going from life in a safe with lots of desiccant to full time exposure to coastal Oregon’s humidity and the resultant swelling of the nylon that caused the problem. The offending buffer is now sealed in a jar with some freshly recharged desiccant. In a week or three, I will return the dried buffer to the pistol for a range session and post results.

It is, indeed, the small things!

October 31, 2009, 09:07 PM
I had the same problem on a STI 40.
I bought a Wilson slide stop with the detent machined in already, cured my headaches...

You can take your old slide stop and file a groove at the upper limit where you see the plunger travels. You need to file just a little detent to keep it from bouncing up.
Nicholson needle files work great.

Chuck Warner
October 31, 2009, 09:18 PM
thats a lot of work for a buff.

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