I have an M&P45 that after I reassemble the gun after field stripping it, I rack the slide one or twice without the mag. I then insert an empty mag to do a function test and the gun does not fire. I need to re-rack the slide after I did the above steps for it to start working in order to dry fire the gun.

What may be the problem?

If I understand your problem correctly, I think your problem is the take down decock lever in the mag well is still down...

When you insert a mag, the lever is moved into it's off position and the gun can then cock.

Easy way to find out would be to take a pencil and move the yellow lever back up after you re assemble the gun... though inserting a magazine is easier.

FWIW

Chuck

After I re-assemble the gun, the take down lever is down. I then rack the slide with the lever in the down position and then insert an empty mag. I would assume the gun then should fire, but it does not. I have to re-rack the slide again with an empty mag in order to make the gun dry fire.

Am I doing the steps in the wrong order? Kinda weird that I would need to re-rack it again to make it work.

It depends what you mean by takedown lever ...

Explaining it with a model in mind which is not equipped with a mag safety ...

cxm seemed to be pointing you in the right direction.

If the yellow sear deactivation lever is in the 'down' position (or pushed forward) it disconnects the sear from the striker.

If it's in the 'up' position (or pushed rearward, as it would be if a magazine were inserted into the mag well, since the mag would push the lever up & rearward back into the sear housing) it allows the sear to connect to the striker again.

However, racking the slide BEFORE you inserted a mag, when the lever was in the down position when the slide was racked, it meant the sear wasn't free to engage the striker. You weren't going to be able to dry-fire the gun even though you inserted mag after racking the slide ... UNTIL you racked the slide again after having the (EMPTY) mag in the (EMPTY) gun.

BTW, the 'takedown lever' is the flat lever you can see on the left, outside of the frame which must be rotated 'down', clockwise, for field-stripping, and which must be rotated 'up', or counter-clockwise, after the slide is reinstalled on the frame.

Now, I may be reading your post wrong, but I suspect you're talking about the sear deactivation lever.

If so, and it remains in the down position when you rack the slide after reassembly, it won't allow the sear to catch and hold the striker's foot. The lever will either have to be pushed up & back or else a mag inserted in order for the sear to once again be 'activated', so to speak, meaning be able to catch the striker's foot.

This means that if you racked the slide with the lever in the down position the striker wasn't caught and held ... and THEN when you inserted the (EMPTY) mag and tried to pull the trigger (on an EMPTY gun) ... nothing happened. No click. The slide had been racked before the sear had been positioned to be able to catch and hold the striker. No joy.

However, when you racked the slide again, but with the mag now in place (meaning the mag had pushed the lever up and back) this time the sear was positioned to be able to catch the striker, and when you pulled the trigger you were able to dry-fire the gun. Click.

I'm sorry if I'm not explaining this clearly, or misunderstood you, but I'm a little distracted by some contractors and some other chores I'm trying to get done between stopping by the computer.

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Ret LE Firearms inst & armorer

The sear will not engage the striker until the lever is raised. ( Either by inserting a mag or with your finger.) That's what this lever is designed to do. Disengage the sear. Your gun is working properly.

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Dave

Elegantly & simply stated ... although I might add 'probably' to the last sentence, since we aren't there to actually inspect the gun.

Maybe I should go back and delete my post as being needlessly wordy.

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Ret LE Firearms inst & armorer

You guys solved it. I was doing it wrong. I was racking the slide before putting the mag into the gun, hence the sear was not activating since it was in the down position.

Fastbolt:

The country is looking for a new set of politicians - you may have a future.

Two words come to mind: Owner's Manual

Nah Fastbolt, The differenece is your retired and have more time to explain things. I'm still working in management and have learned to boil things down by need. Hopefully I live long enough to retire to be as patient (and wordy) as you my friend! ;-)

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Dave

Thanks. Charitable.

I remember having to make presentations and explain things to command & executive level folks, or administrators from other local & state level agencies during meetings. I had to condense info to reach them in the critical short time period before the next bright & shiny object rolled across their vision and distracted them.

Patience in making written explanation is more enjoyable than trying to get someone's attention when they're fidgeting or displaying body language indicating disinterest. The time involved in writing can be metered out however desired, and leisurely walks to the coffee pot or going out and doing something at the bench, can be done in between moments at the key board completing a series of written thoughts. I've even taken time out for exercise, taking the motorcycle out for a ride or wandering down to a cigar club to enjoy a cigar with the guys before finishing writing something on some gun forum.

Of course, since I learned to type on a typewriter, I've been told that my typing on a computer keyboard can be heard at the other end of the house.

I still work with some of the instructors/armorers at my former agency, helping them develop their knowledge and skills, and that happens just often enough that I can satisfy my desire for face-to-face and hands-on experience.

BTW, regarding the earlier politician comment ...

There was a time before I retired when someone said they thought I looked like I worked for the FBI. I'm not sure which comment is 'less agreeable', being told I look like a fed or that I could have a future in politics ...

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Ret LE Firearms inst & armorer

Fastbolt - I think the fact that you KNOW what you are talking about, and give sound advice, disqualifies you from holding political office. Best regards 18DAI.