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Tune/Repair mp40 magazines. Need help


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Hello all. I recently got my mp40 out of jail and took it for a test drive. Of the 12 mags I own, only 3 ran reliably in the gun. Pretty sure it's a mag problem. All my problems were failure to feeds. In some instances, the round would not even be pulled out of the magazine, IE, the bolt would just stop, stuck behind the round, in other instances, the round would be stripped but nosedive into the feed ramp/chamber area and cause a stoppage. (This was regular, off the shelf box ammo, not +P but not underpowered competition loads either) I did have 3 mags that ran perfectly multiple times. For this reason, I'm thinking it's a mag issue and not a worn out bold/recoil spring.

 

I'll try to attach two pictures so you can see when the round was not stripped out, it's also parallel with the mag and not presented at what I would assume would be about a 6 degree elevated cartridge angle needed for the round to pop up into the extractor and chamber. (I'm guessing 6 degrees as that is the angle the STEN gun cartridge is supposed to be presented.)

 

IMG_7731.JPGIMG_7732.JPG

 

I'm posting for any/all to offer their advise. I'm fairly new to the subguns. Additionally, I would specifically like to know if anyone has advise on how to tune mp40 mag lips? Or a source for new mag springs?

 

Lastly, in a previous post in April, huggytree stated, "Folke has the best deal/quality...$100 shipped....he picked out 10 nice Steyr ones...1/2 looked 100% brand new and 1/2 excellent......best quality of any ive seen for sale at any price... i got a bunch for $75-85 3+ months ago....they all work....i dont see those deals anymore...i sold one of those $85 ones for $115 on GB this past week..the marked on MP40 stuff is way up.....for parts/etc for the MP40 all of Folkes stuff is better quality than i find elsewhere.....Bergflak is good for the misc stuff---much of his stuff is NOS"

Can anyone direct me to this website?

Thanks, Scott

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if so many are bad you either really got unlucky with your mags or your gun is touchy....all but 1 have worked in mine and i didnt even bother trying to tune it...if your having problems at the end of each mag its probably the mag spring....give us a pic of bullets in a good mag vs a bad one...are they all mp40 mags or vigneron mags?? (i have a vig mag and it runs 100%)

 

so the 8 mags ive shot in mine...2 needed new springs, 1 had an odd angle to it and wouldnt work.......i got rid of the bad mag (which looked brand new) and replaced springs in the other 2...all of my mags work great....my mags were purchased from multiple sources....

 

some guns like 124 grain only im told...mine runs anything....smooth as glass....maybe you need some adjustment to your mag well latch height?

 

 

http://www.leetoolandmachine.com/springs.html

mag springs

 

http://www.mp40.nl/index.php?page=serial-database

Alex is a great helper/advice!!!!! he has stuff for sale....good guy at the mp40 registry

 

http://www.bergflak.com/mpsale.html

bergflak is also a great help...want NOS parts...he has them..but he is a bit pricey on things..

 

http://www.sturmgewehr.com/forums/index.php?/topic/1010-wts-suomi-coffin-magazines-1115-4450/

Folke has awesome parts/high quality/ fair-correct price.....i got 2 MP40 barrels from him for $450-500 each..1 was NOS(he is out of them now)

 

 

POST SOME PICS AND VIDEO OF YOUR GUN!!!....lets see your new toy!!

Edited by huggytree
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I don't think you necessarily have magazine problems. The top round doesn't appear to be in the correct position for feeding.

 

The ejector performs two functions. It kicks the extracted case out to the side, and it pushes the fresh round forward slightly and holds it tilted upwards, in the correct position in the magazine's feed lips before it's stripped off and fed into the chamber. It looks to me like maybe this ejector has been modified by removing steel from the underside as it has an extra angle in it that my MP-40s don't have. Can't tell for certain from the first photo, but that looks like the problem.

 

My all matching BNZ 41 MP-40 loves 124 gr. NATO spec Winchester (WCC).

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Are you running a factory bolt?? it could be scraping the top of the mag feed lips, is the mag at the correct height in the magwell. Put an empty mag in and pull the bolt back, hold it while you pull the trigger and walk the bolt past the mag lips see if its hitting anything or does it pass over smoothly.There isnt really that much bullet angle on the german mags or the vig mags. Here is a pic of both the vig is on the left. You can get some nice vig mags and use them they might work better because they are in better condition and way cheaper too.Sometimes spreading the feed lips open and cleaning them up with a dremel a little will help the rounds strip off the mag too.

IMG_5455.JPG

Edited by Petroleum 1
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Thanks for the fast response by so many members!

 

Here is my report: Ammo was loaded by a local company called Dynamic Munitions. I ran both 147 and 115 grn FMJ bullets. Both ran fine in my 3 good mags. These loads chrono at a power factor around 140 out of a 5 inch pistol barrel. I occasionally have to tune the feed lips on a 2011 STI Eagle I own and that lead me to believe feed lips could be the problem. But I but don't have any experience running old military surplus equipment. Great advise checking for burrs and cleaning up the existing feed lips. I did find a few nicks and burrs on the edges and have polished them with a stone. Have not been able to test yet.

 

Wow, great idea to run the bolt across the inserted empty mags to see if the bolt is dragging on a magazine that protrudes too far into the receiver. I know, really simply, straight forward stuff but I just didn't think about that. I tested the 9 mags that did not function reliably and 2 of them did drag ever so slightly. As further evidence, the tops of these magazines lips were slightly polished indicating the bolt was wearing the bluing off. Is there a fix to this? Or should I just pass the mags along to other collectors for whom they may be more functional?

 

Regarding the extractor, I believe it is a factory original in unmodified condition but I'm not an expert. I've attached pics, what do you think?

IMG_7826.JPGIMG_7828.JPG

 

Regarding presentation angle of the cartridge, thanks for the correction of 8 degrees on the STEN, I should have referred to my notes before posting incorrect info. Most malfunctioning mags did present the cartridge at a similar angle to the mags that ran flawlessly. I did have a few exceptions. In the attached pic, the mag in the middle ran perfectly, the two mags with tape on them both malfunctioned. The one of the far right is the most extreme example but seems to me the cartridge is going to nose dive when trying to be stripped from the mag?

 

MP40 cartridge angles.JPG

 

All but one mag are original German WW2 issue. None are Vig mags. The one exception is labeled "MP 41 Patent Schmeisser, Haenel" There are no Waffen acceptance stamps on this MP41 mag.

MP41 mag.JPG

 

 

The other interesting mag is a non ribbed stamped 98E from 1940. Guess this missed the rework?

Smooth sided mag.JPG

 

So, as I consider selling/trading some of my non-functioning mags, should I keep the MP41 and the smooth sided mag? Am I fooling myself thinking they are special?

 

Thanks for the link for mag springs. I've placed an order and will test out as soon as they arrive. I'm hopeful it will fix at least a few mags.

 

Now for a little show and tell. The gun has mostly matching serial numbers and is an original 1940 slab sided mag well MP40. The gun is in pretty rough condition. When it first arrived at my FFL, it was bone dry. After taking the attached pictures, I wiped it with Ballistol and have kept it wet since I gained possession. The pictures were under harsh lighting and make the gun look worse than it really is. I know collectors want original guns, however, this particular specimen doesn't have deep pitting. I've considered sending it up to John Andrewski and letting him give it a work over, mainly to stop any further deterioration. I know I'll get different answers from everybody but please share your thoughts regarding if I should keep it original or have it reblued, etc.

 

IMG_0297 copy.JPG

IMG_0317 copy.JPGIMG_0374 copy.JPG

 

I have not included any pictures showing the entire serial number simply because I often see these blurred out on other photos. What is the reason for this? Why don't we want to show the entire serial number?

 

Finally, here is a video showing one of the mags malfunctioning.

 

Thanks again all for your advise. I look forward to your future replies!

 

 

 

 

 

 

 

 

 

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The video link did not play for me. Just me i would keep it original finish. The MP41 mag is nothing special the slab side is a little more rare but they are out there too. Did you take all of the mags apart and service them prior to running them at the range? Maybe they are just gummed up a little. Springs would be a good try on some of them. Edited by Petroleum 1
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that slab side mag is worth $20+ more than the others....

 

id also recommend disassembly and cleaning the guts of the mags...the mags that present the bullet at odd angles...id sell them, move on...or play with them to get them right if its easier for you.....

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Regarding the extractor, I believe it is a factory original in unmodified condition but I'm not an expert. I've attached pics, what do you think?

attachicon.gif IMG_7826.JPGattachicon.gif IMG_7828.JPG

 

 

The angle at which the rounds are being held before chambering looks correct, so the shape and location of the ejector seem to be good.

 

Loading MP-40 magazines pretty much requires a loader for two reasons. First, the double stack, single feed mag design. This was a patented design, used not so much because it worked well (it didn't, always) but because royalties were paid with each gun and magazine made. Same with the Vollmer telescoping mainspring design. A big coil spring would probably have worked better, but that could not be patented. The mag design required the use of very strong springs, too strong to easily load the mag without a loader. To work well, the springs must be pretty strong. I'd suggest pulling the springs out of all our mags and comparing them, side to side, looking for short (weak) springs. I don't recall the minimum spring length in centimeters, but there is one.

 

You're getting a lot of well meaning advice from guys with little experience with the MP-40, except recently, with mismatched guns. It's not always good advice.

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unless all his mags are from the same place i have trouble believing its all mag springs or mags....mine are from 3-4 sources...and of 9 i tried only 2 had spring problems (which after replacing the springs fixes the issue).

 

if all the mags are from the same supplier than its very possible to be a mag issue.....or full of cosmoline/grease

 

id grab some dummy rounds and watch them feed....i know of a gunsmith that video's dummy rounds slamming into the chamber and runs it in slow motion to see whats going on....another idea for you...get a tripod and video it

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I heat cleaned and oiled all my mags. (inside and out) I installed new Wolff springs also. I do not have a single magazine feed issue. I have plenty of mags and have used at least 30 of them.

Eric

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I heat cleaned and oiled all my mags. (inside and out) I installed new Wolff springs also. I do not have a single magazine feed issue. I have plenty of mags and have used at least 30 of them.

Eric

Can you explain the heat cleaning thx Vin Edited by Petroleum 1
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Yes...........i pull the guts and i put a torch thru the bottom for about 5 seconds. Then i use a long screwdriver to push a thick rag thru and pull out the other end. They look new inside after that. I then oil the inside and put it back together with new Wolf springs. I did 88 mags so far.

Eric

 

 

21.jpg

22.jpg

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Let me post an update. I'll try to post a comprehensive report simply for the benefit of future readers to help them a little further down the road if they have similar questions to mine.

 

All my mags have been throughly cleaned although they have been purchased from multiple sources and I have no idea if they are original, replaced springs, different followers, etc.

 

All tubes have waffen Amt. stamps and dated between 1940-1944

 

While I have not installed new springs yet, I'm confident many of my springs are weak. My evidence is that I can hand load at least 30 rounds in most of the mags without using a loader.

 

I compared spring lengths as suggested by TSMGguy. Good call sir. Springs did vary in length. I did stretch some of the compressed springs out at the range but they still did not run. Probably just too far gone? Another interesting observation is that not all springs had the same number of coils. Some had 25 while others had 28. The Springs I have ordered from Lee Tool and Machine are supposed to be +10% power. Wondering if the 28 coil springs were +10% replacement springs at some time or if the Germans varied in the number of coils they ran in these mags?

 

MP40 Spring length.JPG

 

Another interesting observation is that the followers were different. In a mag dated 1941 the rib in the follower was convex while the 1944 follower was concave among other differences. A side by side comparison pic is attached for your reference. Can't really figure out why the 1941 follower is convex. Seems like it should be riding in the concave rib on the mag tube? Any ideas? btw, the mag tube on the 1941 magazine was reworked as it is not smooth sided, it has ribs but they do not extend beyond the reinforced area of the upper mag.

MP40 Follower comparison 2.jpg

 

I'll update once the new springs are installed.

 

And Thanks to Huggytree for the post sourcing new springs. Much appreciated.

 

 

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CAUTION: When test firing recently, we ran a variety of ammo through this gun using the original bolt with firing pin. We then switched to an FPB bolt. The FPB bolt had a lot more resistance when attempting to compress the springs and was much more difficult to draw the bolt back. All to say the springs were more powerful or stronger in the FBP bolt. Having been forewarned by someone (probably Frank Iannamico's book) and always following the rule of keeping your gun pointed in a safe direction, we test fired the FBP bolt at one point using a shooters reloaded ammo only to discover we had a mag dump even though the trigger had been released. The reason for this is the ammo was not strong enough to cycle the bolt back far enough to catch the sear after the trigger had been released. All was well as we dumped 30 rounds into a dirt berm. But had we not been forewarned, it could have been a bad experience. Just a good reminder to always follow the four rules of gun safety!

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Imageaudio thanks for posting this new info. There is some info posted online (maybe this forum too) about the FBP bolts. From what I read the spring is typically cut down a little (how much I don't know) and also the sear grabs the FBP bolt a little different then the stock german one so skipping over the sear is possible. I also read where some people have trouble with the FBP in tube guns only but run in a vintage receiver. If I was you I would keep the testing consistent. Get the gun working with one good mag, bolt assembly and same good ammo. Stick that FBP bolt in a box for now and work on getting just one set up running good. From there you can weed out the other magazine problems and then maybe feed in some different ammo. Maybe try that other bolt eventually... just my 2 cents.

Edited by Petroleum 1
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out of 9 mags only 2 needed new springs on my batch....i cannot load more than 20 by hand on any of my mags...if you can load 30+ it tells me right off you have a bad mag

 

keep the factory setup in the gun until you get this issue figured out

 

i never changed the main spring for my gun yet(but i plan to do this week)...

 

make 1 change at a time.....see the results and then make a 2nd change if needed....clean/change springs/oil your mags and see what it does....

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Thanks for the fast response by so many members!

 

Here is my report: Ammo was loaded by a local company called Dynamic Munitions. I ran both 147 and 115 grn FMJ bullets. Both ran fine in my 3 good mags. These loads chrono at a power factor around 140 out of a 5 inch pistol barrel. I occasionally have to tune the feed lips on a 2011 STI Eagle I own and that lead me to believe feed lips could be the problem. But I but don't have any experience running old military surplus equipment. Great advise checking for burrs and cleaning up the existing feed lips. I did find a few nicks and burrs on the edges and have polished them with a stone. Have not been able to test yet.

 

Wow, great idea to run the bolt across the inserted empty mags to see if the bolt is dragging on a magazine that protrudes too far into the receiver. I know, really simply, straight forward stuff but I just didn't think about that. I tested the 9 mags that did not function reliably and 2 of them did drag ever so slightly. As further evidence, the tops of these magazines lips were slightly polished indicating the bolt was wearing the bluing off. Is there a fix to this? Or should I just pass the mags along to other collectors for whom they may be more functional?

 

Regarding the extractor, I believe it is a factory original in unmodified condition but I'm not an expert. I've attached pics, what do you think?

attachicon.gif IMG_7826.JPGattachicon.gif IMG_7828.JPG

 

Regarding presentation angle of the cartridge, thanks for the correction of 8 degrees on the STEN, I should have referred to my notes before posting incorrect info. Most malfunctioning mags did present the cartridge at a similar angle to the mags that ran flawlessly. I did have a few exceptions. In the attached pic, the mag in the middle ran perfectly, the two mags with tape on them both malfunctioned. The one of the far right is the most extreme example but seems to me the cartridge is going to nose dive when trying to be stripped from the mag?

 

attachicon.gif MP40 cartridge angles.JPG

 

All but one mag are original German WW2 issue. None are Vig mags. The one exception is labeled "MP 41 Patent Schmeisser, Haenel" There are no Waffen acceptance stamps on this MP41 mag.

attachicon.gif MP41 mag.JPG

 

 

The other interesting mag is a non ribbed stamped 98E from 1940. Guess this missed the rework?

attachicon.gif Smooth sided mag.JPG

 

So, as I consider selling/trading some of my non-functioning mags, should I keep the MP41 and the smooth sided mag? Am I fooling myself thinking they are special?

 

Thanks for the link for mag springs. I've placed an order and will test out as soon as they arrive. I'm hopeful it will fix at least a few mags.

 

Now for a little show and tell. The gun has mostly matching serial numbers and is an original 1940 slab sided mag well MP40. The gun is in pretty rough condition. When it first arrived at my FFL, it was bone dry. After taking the attached pictures, I wiped it with Ballistol and have kept it wet since I gained possession. The pictures were under harsh lighting and make the gun look worse than it really is. I know collectors want original guns, however, this particular specimen doesn't have deep pitting. I've considered sending it up to John Andrewski and letting him give it a work over, mainly to stop any further deterioration. I know I'll get different answers from everybody but please share your thoughts regarding if I should keep it original or have it reblued, etc.

 

attachicon.gif IMG_0297 copy.JPG

attachicon.gif IMG_0317 copy.JPGattachicon.gif IMG_0374 copy.JPG

 

I have not included any pictures showing the entire serial number simply because I often see these blurred out on other photos. What is the reason for this? Why don't we want to show the entire serial number?

 

Finally, here is a video showing one of the mags malfunctioning.

attachicon.gif MP40 malfunction.MOV

 

Thanks again all for your advise. I look forward to your future replies!

 

 

 

 

 

 

 

 

 

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Hello, and thanks for posting. I like the original finish on the gun and if it were mine I would not refinish it. I would just keep a thick coat of oil on it when not in use. I am lucky enough to own a pair of C&R guns one with original finish and one reblued. I like them both but once it is refinished part of its history is lost forever. The original finish is just way cooler. Is there any way you could post more pictures like the top of the receiver plus a left and right side view? Also could you maybe tell us about how you got it and what you know about the gun? Also you might want to contact Alex Cruiming from Holland and give him your serial number to put in his database. He is very helpful if you have further questions. Take care and thanks for posting. Haenelistklasse

 

PS What parts are matching???

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Springs are always the first thing to suspect, especially if the gun is all matching and otherwise in nice shape. Besides the mag springs, there are two others that are critical. These are the two springs inside of the Vollmer telescoping mainspring housing. The mainspring is obvious. There's a smaller, stiffer spring which should be felt when the bolt is drawn all the way to the rear, just as the bolt reaches the safety notch. This is the buffer spring. It both slows down the bolt at the rear if its travel, and accelerates the bolt to insure that pick-up and chambering of the next cartridge are positive. If the springs on your gun are in really nice shape, then a mildly loaded cartridge with a 115 gr. bullet may not fully compress the main spring, and the bolt may not engage the buffer spring at all. Conversely, if the bolt's main spring has gotten a bit weak, then 115 gr. might work fine, but rate of fire may be very slow because the bolt never engages the buffer spring. If you're not sure the bolt is engaging the buffer spring, put a piece of masking tape over the bolt slot where the buffer spring starts to be felt. If the tape isn't torn after firing, the bolt isn't going fully to the rear.

 

I've sold of my mismatched and tube guns, and kept only the one all matching bnz 41 MP-40. The staking on the mainspring housing is undisturbed. The springs are strong, all of them, including the mag springs. The gun doesn't particularly like Winchester white box 115. It prefers NATO spec 124 gr, and really likes the full power Russian steel cased 124 gr. ammo made under the Ulyanovsk name, but this can't be found new any more. It has a bullet with an almost triangular cross section in the nose (as original P.08 ammo had), which insures positive feeding. Lots of the stuff show up for sale from time to time, and I pick it up if the price isn't outrageous.

 

So, MP-40 feeding problems? Look first to springs and ammo.

 

One time, just for the hell of it, I loaded a mag with Norma 90 gr. 9mm. The gun shot fine, with a slow rate of fire, but the bolt didn't move rearward far enough to engage the sear. The gun just ran until the mag was empty.

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