40c Firing Issue

[Coastie762]

Well, I went to the range today with my "fixes" and I am pleased to say that the slide drag appears to be gone. I am not sure if it was the work I did on the mag or the fact that I adjusted the spring tension on the slide stop lever...or both, but the gun is 100% better. I also brought a brand new 10 round mag with me which had never been used. With the new mag I felt some slide drag...but a little less than I was experiencing with the original 10 round mag. I measured the distance across the feed lips of the new mag and it was only a hair narrow compared to my 15 round mag which gives me no problems. I will try to adjust the new 10 round mag just like I did to the other one.

Anyway, it looks pretty good at this point.

By the way I used my 9mm barrel and 12 round 9mm mag today and the gun shot great, without a single issue. The gun almost makes a better 9mm than it does a 40 cal. I seem to be more accurate with it as a 9mm.

That's good to hear! How much did you tweak the slide stop spring?

My replacement slide stop and Apex parts should be here tomorrow. Unfortunately, due to family commitments, I probably won't get a chance to try it out immediately. If things work out, I may be able to get to the range Sunday.

Glad to hear the 9 mm set up works well for you. I have a 9C that has been dead nuts reliable, accurate and is my current CC weapon of choice.

 

[Mikey217]

I'm just back from the range, where I did a little bit of testing myself. I had about 78 hand loaded 165 gr plated bullets with 6.4gr of Power Pistol, which I fired without any issues at all. The average velocity for this batch was 949.7 fps. I had 22 rounds of hand loaded 180 gr FMJ bullets with 7.4gr of HS-6, which caused a lot of problems. I had 4 mags of 5 rds each and one mag with 2 rds. In mag 2 and 4, the slide caught about 1/4 " before battery for a few seconds then went the rest of the way. Both times, though the striker wasn't reset, so I had to pull the slide back a bit to reset the trigger. On mag 6, this same thing happened on rd 1 but not rd 2. I then fired about 50 rds of 180gr American Eagle, without any issues at all. This was odd, because last time I was at the range (last week), all I fired was this same 180gr American Eagle, and it did the same 1/4" pause before battery about 6 times out of 50 rds.

On the 180gr hand loads, I did ensure that I had a good grip on the weapon at all times. The shots were fairly accurate, as well. I didn't get a velocity reading on any of the shots this time out, but last time I took the chrony with these same loads, the avg was about 1300fps.

With the 180gr factory ammo, I got an avg velocity of 812fps.

So... I believe this goes back to my earlier complaint that neither S&W, nor third parties, do not supply any optional recoil springs for this weapon. I think that maybe the 1300fps ammo is maybe too much for the supplied spring. Granted, this is a little hot for my taste anyway. I'll probably stick with the 165gr Power Pistol loads from now on, since they performed so well. I still have a LOT of 180gr FMJ's, so I'll just back off quite a bit on the HS-6 to see if I have better luck. The fact that I didn't have any problems with the same factory ammo that I did have problems with last week sort of leaves that piece of the puzzle inconclusive.

My next task is to mimic the changes that xzhyncmade to his mags and slide stop spring. I'll report back again after that (I usually go to the range once a week).

 

[xzhync]

That's good to hear! How much did you tweak the slide stop spring?

My replacement slide stop and Apex parts should be here tomorrow. Unfortunately, due to family commitments, I probably won't get a chance to try it out immediately. If things work out, I may be able to get to the range Sunday.

Glad to hear the 9 mm set up works well for you. I have a 9C that has been dead nuts reliable, accurate and is my current CC weapon of choice.

I didn't adjust the spring much...just opened it up a bit to create a little more tension. Maybe 5 or 10 degrees. I can tell it made a difference. When pushing up on the slide stop (with the slide removed) it pops back in place with a little more authority now. It didn't seem all that bad before I adjusted the tension, but after the tweak I just can't imagine that the recoil could bounce it hard enough to move into the path of the returning slide.

I would also suggest working with your mags to reduce the spring tension a bit. Make sure the feed lips are wide enough to allow the round to be easily stripped off. Hand cycle a mag full rather slowly and watch the round feed into the chamber. To me it appears that the round needs to be able to move forward and a bit upward at the same time. The feed lips on the 10 round mag were about 1/32" narrower than on the 15 round mag. The narrower feed lips seemed to impede the ability of the round to move upward. I could be off base, but that was my observation. Once I shortened the mag spring to lower tension and opened the mag feed lips slightly (along with the adjustment to the slide stop spring) the problem went away. Now it cycles very smoothly. I mainly shot American eagle 165 gr fmj, but also shot some very hot Underwood 155 gr jhp's.

 

[mrk0830]

I simply cleaned the **** out of my 40c and dissasembled and cleaned the mags. Oiled everthing perfectly. Shot 148 ppu hp bringing my round count to 350 total. The gun ran like a sewing machine. Accurate ashell from 5 to 40 feet. Trigger has become even smoother. Still cant handload mags so i have been using uplula loader. Do these springs ever get easier??

 

[Coastie762]

I appreciate the info. My parts showed up today, so I'll likely start with tweaking the slide stop spring in the manner you suggested. I'll try that prior to making any modifications to the magazines.

That way I can gauge the impact of each modification to see what makes the largest difference, if any.

 

[xzhync]

I appreciate the info. My parts showed up today, so I'll likely start with tweaking the slide stop spring in the manner you suggested. I'll try that prior to making any modifications to the magazines.

That way I can gauge the impact of each modification to see what makes the largest difference, if any.

I am looking forward to your assessment once you start applying fixes.

 

[Coastie762]

I managed to get out briefly this morning, but the weather has been rainy and windy all weekend. Not conducive to much more than a quick function check.

I had tweaked the slide stop spring on both my compact and full size .40s. The FS also contained a new Apex Failure-resistant Extractor that had not been tested.

I fired 20 rounds of 180 grain Federal FMJ and approx the same amount of 180 grain Blazer Brass. An addional 5 rounds of Win PDX1 165 grainers were fired as well. The good news is that the premature slide stop lock back went away. I did, however feel a couple of the hesitations as the slide went forward, more so with the Federal than the Blazer. They seemed less abrupt than previously felt; that may have been due to the different lot of ammo (or me hoping it felt better).

No handloads were fired due to the generally foul weather.

The FS was also fired with approx the same amount and mix of loads. That pistol ran flawlessly during its brief test. Previously it was exhibiting some of the slide "hesitation" on the forward stroke, as well as damaging some case mouths on ejection, particularly with full power loads. Today the pistol cycled very smoothly with much improved ejection and no damaged case mouths.

I'm now considering popping the extractor off the compact to see if there are any burrs or sharp edges present. Perhaps something may be causing brass to briefly hang up as they start to slide under the extractor hook as they are chambered.

Conclusions so far indicate the slide stop spring is a causal factor in the premature slide engagement with a partially full magazine. The link to the hesitation or jerky forward slide movement is to me not as definite.

As stated above, my next step is to inspect the extractor and if necessary stone any burrs or sharp edges found. I will also check function with handloads of varying power levels when the weather cooperates.

If the problem persists then the next step is to look at adjusting the magazines.

 

[jake1530]

I have had my 40 since August, and it has been doing that infrequently since even with different shooters. I have narrowed it down to Federal Eagle 180 grain bullets, all other work great. Now I have a different problem. Sometimes when I load a magazine the slide moves forward by itself.

 

[Coastie762]

Jake1350, When you have the slide auto-forward, how are you inserting a magazine? This condition is noted to happen when you seat a mag "forcefully". My M&Ps will sometimes do this when slamming a magazine home. Some more often than others.

 

[Coastie762]

Regarding the slide motion I have experienced, after a month of tinkering with both my 40 FS and 40 C, I have made more or less a circle and have gone back to wrist support when shooting offhand as a major contributing factor.

The premature slide lock I had experienced with the compact disappeared after adding tension to the spring.

I shot quite a few rounds off an old plastic Hornady pistol rest over a chronograph, testing both .40 and .357 Sig loads. When pressing the pistol firmly into the rest, NO slide hesitation was felt when firing, regardless of the number of rounds in the mag or load fired.

When firing the same loads offhand, the heaviest loads would start to experience the "hesitation" with 5 or 6 rounds in the mag. When I deliberately left my wrist more "loose", the feeling of hesitation would worsen. Again, as I mentioned in a post above, my wrist strength is not the greatest to begin with.

I also had a moment of enlightenment the other night when unloading some full .40 mags after a cancelled range outing. As I started shucking the rounds out, spring tension was fairly light until there were six rounds left in the mag. The tension at that point actually seemed to increase dramatically. This was repeated in each of the mags, full size and compact that I was unloading, probably a dozen total. It appears that the shape of the mag body contributes to this condition. The five-round point is approx where the mag body starts to funnel down.

The increase in mag tension at that point would increase slide drag. Couple that with a "less than firm" grip and this would reduce slide travel and may account for the slide hesitation felt.

This may also confirm why reducing magazine spring tension by either clipping the springs as reported by some or repeated use results in improved operation.

Please try this for yourself and let me know what you think. Simply load the magazine to capacity. Slide the rounds out one at a time and note the approx force required to slide them out. If you feel a change, note how many rounds were left in the magazine when the change was felt.

 

[xzhync]

Coastie...that is exactly what I observed with the increasing mag tension at the 5 to 6 mark. I had to clip 2 coils off of the mag spring to eliminate the slide hesitation. I tried clipping only 1 coil, but that didn't quite do it. I have 2 of the 10 round mags and found the both needed 2 coils clipped. I noticed the problem with both 40 and to some extent 357 sig. With the 9mm mags there was never any slide hesitation so I left those mags as is.

 

[DocSunShine]

I had it happen a couple times during the first 100 rounds, hasn't happened since, not really sure you could call it a malfunction, since it did feed, go into battery and fire. I think it's not uncommon during the "break in period". I know a lot of M&P owners don't want to hear that, but all guns should be broken in prior to carry anyways. I love my 40c and trust it with my life, great gun.

 

[jake1530]

I have a whole thread on this with my 40c. I believe its the fedreal ammo look at the shape then compare it to other brands. It's just a round ball head with the tip cut off, not shaped like a true hollow point. My suggestion try different ammo.

 

[F4UCorsair]

I'm curious if what I've been experiencing is what was talked about in this thread. I've had my M&P 40 FS for 2 months. About half of the time (I haven't really documented how often) the slide travel forward feels "slinky" or "bungie"-like if that makes any sense. Though that bungie feeling seems to come at the end of the slide traveling forward, and not during the brass ejection process back by the slide stop. It never has any problem firing, ejecting, or going into battery. I'm pretty sure I'm not limp wristing, but it's not impossible. The gun shoots really well. But that bungie-like feeling as the slide travels is odd in comparison to other guns I've shot or own (including the M&P Shield).

 

[MSG Glenn]

This thread has really scared me. I have a 40C on order & waiting delivery which could take up to 1.5 months more. I almost feel like cancelling the order. I had a Glock 23, my duty gun, which I gave to my son before Wisconsin had a concealed carry law. Mistake. When the CC law was enacted I bought a Sigma 40VE. That's all I could afford. Works perfectly. My neighbor wants the Sigma very badly & will pay me full new price for it. I had thought that S&W put out a good dependable product right out of the box. . I guess I was wrong. Maybe I'll go with the pricier Glock 23 Gen 4. My self defense depends on it & plan on doing loads of range fire, hopefully several hundred rounds/week. I knew it was too good to be true. My son is a PO & issued the M&P 40 so he & I thought the 40C would be just as good. Wrong again. What happened to American craftsmanship? Put the product out & let the buyer do the QC. I won't deal with those companies.

 

[MSG Glenn]

I have a whole thread on this with my 40c. I believe its the fedreal ammo look at the shape then compare it to other brands. It's just a round ball head with the tip cut off, not shaped like a true hollow point. My suggestion try different ammo.

I realize that this post is several months old but I have a whole boatload of Federal ammo, JHP & the type you mentioned for practice & a M&P 40C coming eventually. As my earlier post has stated I'm really getting scared & feel I should cancel the order & go with Glock.

 

[Fastbolt]

I own a 40c from '09 production that exhibited early lock-back with rounds remaining in the mag.

As an armorer, I contacted S&W and discussed my problem.

Recoil forces cause what's called "parts flutter". In the case of the slide stop lever, this means the lever bounces up & down to some degree (against the spring tension of the lever). The lever spring has to exert sufficient force to prevent the lever from rising high enough to engage the stop notch in the slide. (Unless, of course, it's being over-ridden by the spring & follower in an empty magazine.)

Ordinarily, this isn't a problem, but in the small 40c & 357c they apparently discovered that the increased recoil forces of those cartridges can sometimes overcome the spring tension. They came up with a heavier slide stop lever spring. The original spring in the 40c was painted light blue. The revised, heavier new spring is painted yellow.

I learned in a M&P armorer recert that the "standard" slide stop lever assembly, with the yellow wire spring, is going to become standard throughout the M&P line in the future. (FWIW, since the '06 introduction of the M&P pistol line they've gone through plain/unpainted, red, light blue and now yellow painted wire springs in the slide stop lever assemblies, depending on the caliber models.)

I was originally told (in '09) that they were concerned the heavier yellow wire spring might be too strong in the average 40c, and might lead to the opposite problem, meaning the slide wouldn't lock back when the mag actually ran empty (meaning the mag spring/follower might not be able to overcome the tension of the heavier slide stop lever wire spring). They were only replacing the standard light blue spring assemblies with the yellow spring assemblies on a case-by-case basis at that time.

If a 40c is having a problem with early slide lock-back, it can also sometimes be related to: Shooter thumb (bumping against/upward on the lever tab); or; Ammunition (wide nose/ogive bullet).

No reason to start clipping magazine springs! That can lend itself to other functioning problems. The spring rates have been determined by S&W engineers, and manufactured by Mec-Gar, to exacting rates for the needs of the M&P 40c.

I have one of the latest revision slide stop lever assemblies in my own 40c, and between it and the previously revised assembly (with the earliest use of the yellow wire spring), I haven't had any further slide early lock-back.

Yes, upon rare occasion I can "feel" a slight slowing of the slide's return-to-battery ... but it doesn't fail to feed, or fail to go into battery, and it doesn't lock back early with rounds remaining in the mag anymore. Since I've encountered the same sort of slight slowing, or hesitation, in cycling in some other guns, I suspect it's just "one of those things". As long as it's not a problem ... it's not a problem.

Call the company back and ask for the gun to be returned for further inspection. Clearly state in your letter that your slide is locking back early with ammunition remaining in the mag (if indeed it is doing that, of course), and ask for it to be correct

Be certain your thumb is NOT involved. (I've watched some shooters SWEAR their thumbs weren't bumping the lever tab, but as the frame snapped upward under recoil, I saw their thumbs hit the lever tab without them feeling it.)

Use good quality ammunition made by one of the major American ammo companies.

Make sure your recoil spring assembly hasn't been damaged, and that you haven't tried to disassemble it. (Obviously, make sure the assembly is properly installed when the gun is reassembled after being field-stripped).

Normal lubrication should be present (which also means not inside the mag body, where it could accumulate and introduce feeding issues, which can also slow feeding and slide travel).

Make sure the extractor is clean & DRY. Excessive solvent/CLP may contaminate extractor recesses and create functioning issues at some point. Not to mention slowing feeding for the case rim to slip under within the extractor hook.

I've seen a fair number of 40c's come through the range since I bought mine, and they've all ran fine. I suspect the occasional issue with early slide lock-back on a 40c (and 357C?) might be a case of an occasional gun needing to be checked for burrs, as well as needing the heavier (yellow) slide stop lever wire spring.

I wouldn't be surprised if this is the reason the standard slide stop lever spring on new production guns is going to be the yellow wire spring ... (but another revision to the assembly is the new angled bend of the right side lever, so it presses against the trigger bar and lends some extra tension against it as it slips back under the sear nose - aka, more "reset" ). I suppose they decided they can use the heavier wire spring without it introducing any other issues.

Dunno what's happening with anybody else's particular gun, but I thought I'd mention my own experience and some thoughts.

I'd also suspect that since they've finally introduced the Shield 40, they've probably gotten a hand on the recoil force effects on the little M&P's chambered in .40 S&W.

 

[MSG Glenn]

I'm not sure if that reassures me, Fastbolt. I assume S&W has good customer service, will honor the warranty & will attempt to fix a firearm that's defective. In my case if I need to send my M&P in for repair if it's not completely dependable I'd be unarmed. I can only afford one gun at this time. My Sigma will be bought by my neighbor. He's as anxious to get that as I was anxious to get the 40C. Now I don't know. I got a good deal on the 40C from Streicher's along with Trijicon night sights & 3 mags with a LEO/Security/Military discount. I can't get a deal like that from Glock or any other gunstore. Streicher's no longer handles Glock since the Milwaukee PD stopped using them. I'm really in a quandary. I guess I'm spoiled wanting a working piece of equipment right out of the box especially if my safety & that of my family depends on it. I'm sorry S&W has sunk to the level of those companies that depend on their customers to perform their QC.

 

[Fastbolt]

If you think that other gun companies don't have similar potential issues arise with their products, you need to be around more firearms. I won't mention another couple of makers of plastic-framed pistols, for which I've also attended several armorer classes over the years, and what's happened with new guns every now and again in their product lines ... including some I bought with my own money.

I've been through more than 20 armorer classes for an assortment of firearms commonly seen in LE work (pistol, revolver, rifle & shotgun). I've seen - and listened to other armorers & firearms instructors relate - minor problems that can occur with even NIB guns. It happens.

Ever hang around the service dept isle of any of the car dealers? Talk about staking your life on properly functioning mechanical equipment every day ... and none of the mechanics are ever bored or lacking for work, are they?

 

[Dino1]

Not same problem, but very close to it. I was haveing the slide hang up a little when going into battery, I was shooting 180gr. ammo and it did it quite frequently, never failed to feed. I then switched to 165gr. ammo and have not had the issue as of yet. I am still breaking in this firearm, and still experimenting with different ammo. But I think the more high powered ammo in these may be a problem. I am going to do more testing, as I still have about a 1000 rounds of 180 gr. and about 750 rounds of 165gr. I am going to switch back and fourth with them and see if it makes a difference.