Seems this is asked about every other day, so let's address some of the possible reasons:

Shooter's thumb interfering with slide catch lever.
Shooter not holding pistol firmly.
Shooter failing to clean and lube the pistol.
Damaged magazine follower.
Damaged slide catch lever.
Damaged/worn arresting notch in slide.
Severely worn magazine spring.
Underpowered ammunition (especially in conjunction with some of the above issues).

I suppose an overly stout recoil spring could cause this, and some new pistols seem "tighter" than others which could contribute.

Placing the recoil spring on backwards (the tight end goes on the guide rod first) could conceiveably affect slide speed enough to cause this, although I haven't personally witnessed it.

Checks: with the slide off the pistol, lift the slide catch lever; it should be under spring tension and should smartly return to it's rest position when released. (If it doesn't, the slide catch lever spring is broken or missing). Insert an empty magazine and ensure that the follower of the mag lifts the slide catch lever up. With an assembled pistol with slide forward, insert an empty magazine and rack the slide to the rear; the slide should remain locked back.

quote:

Originally posted by Chris Orndorff:
ith an assembled pistol with slide forward, insert an empty magazine and rack the slide to the rear; the slide should remain locked back.

This test allowed me to identify another unusual cause of the slide failing to lock back with a P220: an overly-stiff slide catch lever spring.

During our first training session after a deputy was issued a new 220, he experienced failures of the slide to lock open with the magazine empty. I had serviced the gun when we received it, including a detail strip and thorough cleaning and lubrication. When the gun was fired, the slide would lock open with an empty magazine sometimes, but not always. When I checked it by manually cycling the slide with an empty mag, I found that the slide catch lever was pushed up only far enough that it would just barely engage the slide intercept notch.

The problem happened with all magazines I tested, new and old, and I confirmed that there was nothing interfering with the slide catch lever or spring.

I finally tried a slide catch lever spring from a different gun: problem solved. I obtained a new slide catch lever spring from SIG and it, too, worked fine.

The tests Chris describes are important for narrowing down and ultimately determining the cause of the problem. In addition, the following are important questions:
1. Does it happen with all ammo? If not, what kind of ammo does it happen with?
2. Does it happen with all magazines? If not, what's the story of the magazines? Are they new, used, after-market?
3. Have I changed any parts of the gun?
4. Is the gun new or used? If used, how many rounds? If new, was it cleaned and lubed before first use? If used, was it cleaned and lubed after the last time it was fired?
5. Does it happen when I shoot the gun left-handed? Does it happen when someone else shoots it?
6. How many times did it happen?
7. What were the results of the function tests Chris recommended?

quote:

Checks: with the slide off the pistol, lift the slide catch lever; it should be under spring tension and should smartly return to it's rest position when released. (If it doesn't, the slide catch lever spring is broken or missing). Insert an empty magazine and ensure that the follower of the mag lifts the slide catch lever up. With an assembled pistol with slide forward, insert an empty magazine and rack the slide to the rear; the slide should remain locked back.

Thank you. Thankyouthankyouthankyouthankyou

i am having the same problem with my new p220. the slide will lock back manually with two of the 3 mags that came with the firearm. do i have a bad mag? is the spring weak? should i try taking apart the mag and stretch the spring? or should i just return the mag and get a new one?

quote:

Originally posted by drmac:
do i have a bad mag? is the spring weak? should i try taking apart the mag and stretch the spring? or should i just return the mag and get a new one?

If it's one bad mag, why don't you first swap its follower with that from another mag. If the problem doesn't change with the follower, then you might swap the magazine's spring with the spring from one of the mags that works.

Excellent post Chris.

After about 4k rds. thru my 226, my slide would not lock back everytime. I was able to solve the problem w/ info gleaned from these types of topics.

What was the problem you ask?
Yup, right thumb riding the slide catch lever (right hand shooter).

I am now in the process of learning to capture my right thumb under my left thumb when I grip the pistol.

I appreciate all of the things I learn on this board, from the abundant supply of info from knowledgable members.

This message has been edited. Last edited by: xr650,

quote:

Originally posted by Jane:

quote:

Originally posted by drmac:
do i have a bad mag? is the spring weak? should i try taking apart the mag and stretch the spring? or should i just return the mag and get a new one?

If it's one bad mag, why don't you first swap its follower with that from another mag. If the problem doesn't change with the follower, then you might swap the magazine's spring with the spring from one of the mags that works.

i took apart the mag and notice the spring was not in the same shape as the other mag springs. so i bent it to look like the other ones and now the slide locks back for all three mags. thanks for the reply my only question is why did this happen on a brand new one. is quality control really become that bad?

Chris, excellent post!

I had the same issue with my P-239/.40. I tried all the things Chris mentioned, and ended up sending the gun back to Sig (the work invoice returned with the fixed gun said the slide catch lever was 'out of spec').

The point is, I listed in my phone conversation with Sig customer service (and in the letter with the gun when I sent it in) all of the things I'd already tried (things that Chris mentions), so I felt they more-readily accepted that there really might be a problem with the gun, and thus, they did not blow me off as the problem being an "operator technique/error" thing. FWIW.

I think the sticky glue wore off this one.
Let's hammer it back to the top once.

i have tried all the above suggestions. i think something might be wrong with the slide catch lever spring. after shooting the pistol for qualifications my slide will not lock back with an empty mag. if i slam the slide back and hold it open for a second the slide catch lever will engage. any suggestions? this is a new p220 45cal with only 150 rounds of ammo.

quote:

Originally posted by drmac:
i think something might be wrong with the slide catch lever spring.

quote:

Originally posted by sigfreund:
When I checked it by manually cycling the slide with an empty mag, I found that the slide catch lever was pushed up only far enough that it would just barely engage the slide intercept notch.

When you pull the slide back with an empty magazine, does the slide catch lever move all the way up into the intercept notch? If not, your problem sounds exactly like the one I described and which was due to an overly-stiff slide catch lever spring. Since my own experience, I've read of a couple of other incidents that were evidently due to the same reason. Check it with all the magazines you have available, and if it happens that way every time, I'd bet serious money that it's a spring problem.

i called sig today and they are sending me a new catch spring. the spring seems to stiff for the slide to push it up.

quote:

Originally posted by sigfreund:

quote:

Originally posted by drmac:
i called sig today and they are sending me a new catch spring. the spring seems to stiff for the slide to push it up.

Please report your results with the new spring.

i will let you know what happens

quote:

Originally posted by Chris Orndorff:
Seems this is asked about every other day, so let's address some of the possible reasons:

Shooter's thumb interfering with slide catch lever.
Shooter not holding pistol firmly.
Shooter failing to clean and lube the pistol.
Damaged magazine follower.
Damaged slide catch lever.
Damaged/worn arresting notch in slide.
Severely worn magazine spring.
Underpowered ammunition (especially in conjunction with some of the above issues).

Aftermarket mags

Using grease in cold weather

Thumb brushing the slide

Mr. Orndorff,

Any chance you can lock your thread at the top of the page.

quote:

Originally posted by HOG4DNR:
Mr. Orndorff,

Any chance you can lock your thread at the top of the page.

I don't have keys to the pin-posts-at-the-top-of-the-page machine .

quote:

Originally posted by Chris Orndorff:

quote:

Originally posted by HOG4DNR:
Mr. Orndorff,

Any chance you can lock your thread at the top of the page.

I don't have keys to the pin-posts-at-the-top-of-the-page machine .

chris, if i put something in the slide catch release, forcing it open and leave it like this for a week. do you think i might beable to weaken the spring some? i feel this is the reason the mags won't always force the slide catch up enough to lock in the slide.

Great post Mr. Orndorff. Thanks for the guidelines that you posted. It sure helps to narrow it down. Now I know how to prevent it.

Thanks you very much.

quote:

Originally posted by drmac:
if i put something in the slide catch release, forcing it open and leave it like this for a week. do you think i might beable to weaken the spring some?

I doubt it. I don't think this will tension the spring far enough to make a difference. Won't hurt to try though. Thought you had new springs coming?

quote:

Originally posted by Chris Orndorff:

quote:

Originally posted by drmac:
if i put something in the slide catch release, forcing it open and leave it like this for a week. do you think i might beable to weaken the spring some?

I doubt it. I don't think this will tension the spring far enough to make a difference. Won't hurt to try though. Thought you had new springs coming?

hi chris, the spring just arrived in today's mail. i was hoping i didn't have to have the pistol torn down(it is brand new), but i guess i have no choice.