Getting jams with 40S&W during part of magazine.

[tazman]

I have a Taurus PT100 with a Beretta 96 barrel in it. I purchased a couple of MEC-GAR magazines for it. Using these magazines has been frustrating and I don't know how to correct the problem.
I am using a couple of different loads that have the same issue. The first is a Lee 175 TC with standard lube grooves. The second is a RMR plated round nose bullet.
Both loads pass the plunk test easily. Both never fail to eject or lock open on last round.
The problem comes during the first few rounds when the mag is full. I get 3 point jams where the nose is in the chamber, the rim of the case is still sitting at magazine height and the middle of the case is jammed against the feed ramp on the back of the barrel.
The frustrating part is the last 5-6 rounds in the mag function perfectly in every instance. It doesn't matter which mag I use, they all do this.
It also doesn't matter what the OAL of the cartridge is. I have loaded them long enough that they barely fit in the mag and short enough they looked funny and every where in between.
I get 50% jams in the first few rounds and the last 5 run perfectly.

Does anyone know what is causing this? Is there an easy cure or even a difficult cure for it?
I don't know what to try.

Just as an experiment, I loaded the magazine full of 9mm rounds and ran it through my PT92 and it ran flawlessly for 3 magazines full(60 rounds).
The mags are stamped 40 S&W.

[Virginia John]

tazman, I have personally never encountered this situation but based on your explanation, it sounds like the mag spring may be your problem. When the mag is fully loaded the spring is the most compressed and as the number of rounds decrease so does the pressure and things start functioning as they should. If it were me I think I would try shortening the mag spring and see what happens ( only a little at a time).

[35remington]

Weakening the mag spring is asking for feed problems with the last rounds in the magazine. Usually three point jams are due to feed lip geometry and low feed ramp strikes possibly combined with OAL issues. First thing to try is to seat ammo to the absolute max OAL your magazine and chamber will allow and try again. I do not know how close to max you were skating but can offer only this as a cure for the ammo itself. Shortening the ammo is going in the wrong direction.

Longer OAL means a higher ramp strike and less angularity in feeding. Evaluate magazine lip correctness by trying common factory ammo. If it won't function with that you've got range only magazines. Release timing is slightly variable as the magazine empties due to the pressure of the rounds against the feed lips changing as the magazine empties. Release timing is earlier when the magazine is full by a slight degree but if correctly formed straight feed lips with a timed release point is present there is little you can do to change the magazine.

Don't modify the springs or you'll shortly be buying new ones due to last round misfeeds. Do everything to adress the problem with your ammo first before making modifications that cannot be undone.

It is possible the temper of the magazine lips is poor, making the magazine body less springlike, which is essential for proper feeding. Bottom line is probably a release timing issue.

[376Steyr]

I think I see a pattern here.

http://castboolits.gunloads.com/showthread.php?281639-Recent-disappointment-with-Taurus-service

[Petrol & Powder]

35remington is right on the money. The higher force exerted by the fully compressed mag spring is distorting the geometry of the feed lips. As the force decreases (fewer rounds in the mag) the feed lips move closer to their correct relationship and the magazine feeds correctly.
There's more metal at the top of the 9mm mag which is why they work.
MEC-GAR magazines are generally ok but anyone can make a mistake. If you don't mind risking a magazine, you could try reforming the magazine lips slightly. I would use a pair of stout needle nose pliers to add just a little more curl to the feed lips. Don't get carried away, the round still needs to be released when the feed rib pushes the round forward and the feed angle needs to be close.
You could also try re-tempering the top portion of the mag after you get it right.

[Walkingwolf]

If it is not OAL, I suspect that the mag springs are still not broken in, and possibly there is not enough umpf in your loads. There is a reason hotter loads feed better in most guns. What are your loads.

[Petrol & Powder]

If it is not OAL, I suspect that the mag springs are still not broken in, and possibly there is not enough umpf in your loads. There is a reason hotter loads feed better in most guns. What are your loads.

No offense but he's not having a functioning problem related to the cartridges being underpowered. If that was the case the pistol wouldn't cycle with the last few rounds in the magazine. Not to mention he can see the feeding issue. He's got plenty of slide velocity to make the pistol cycle with the last 5-6 rounds in the mag.
As for magazine springs needing to "break in"? I'm not sure what you're talking about. I've used 100's of magazines in my life and never had one that needed to "break in", whatever that means.

[tazman]

These mags are the extra capacity ones by MEC-GAR. I thought it might be the springs were too tight except then it should feed the last 10-12 fine instead of just the last 5.
Also I used these same mags in my 9mm loaded with 20 rounds each of reloads and they worked perfectly(talk about a high capacity magazine).
Odd that they will work with both 9mm and 40 S&W but they do.

[Petrol & Powder]

It's clearly feed angle and release timing.
As a test, disassemble the barrel from the slide and install just the barrel on the frame. The barrel has rails on it that mate with grooves in the frame. Push the barrel all the way back until it contacts the frame and the locking block tilts down. NOW, with just the barrel on the frame and no slide, seat a loaded good magazine into the frame and note the relationship between the top round and the breach of the barrel.
Then remove that magazine and insert a fully loaded MECGAR mag and note the relationship between the top round and the breach of the barrel. I'm willing to bet the fully loaded MECGAR magazine positions that top round at a noticeably different angle.

You want that top round in the offending magazine to be in the same relationship as the top round in a known good magazine.

Remember on a Beretta 92/96 series (The PT100 is a copy of the 96) the barrel doesn't unlock by tilting like it does in a Browning design. In the Beretta design (copied from the Walther P-38 by the way) the barrel moves linear with the axis of the slide and only the locking block tilts to perform the locking and un-locking function. The feed angle isn't completely in-line but it's very shallow by design.
Bullet nose shape may have some affect on feeding but for the most part the Beretta design is very tolerant of different bullet shapes. I had a Beretta 92SB that would consistently feed empty casings into the chamber during malfunction drills.

[Petrol & Powder]

145920Beretta 92 showing the relationship between the barrel and the top round. [Slide removed for demonstration]

[tazman]

Thanks. I will try that when I get home.
I am currently off visiting my newest great-grandbaby. Family and SWMBO take precedence.

[Petrol & Powder]

UNDERSTOOD, carry on

[tazman]

Petrol&powder, I want to thank you for making me think about what was happening with the magazines instead of running on assumptions.
I was working with just the Mec-Gar magazines and had neglected to test them against the original Taurus magazines. I never had this kind of problem with the Taurus factory magazines but it had slipped my mind. All the ammo I have feeds perfectly using the Taurus mags, and now I know why.
I took pictures of the Taurus magazine and compared it to the Mec-Gar magazine and several differences were immediately obvious.
146155146156
The first image is of the Mec-Gar magazine. The second is the Taurus magazine which feeds flawlessly. There is quite a difference in how each magazine presents the cartridge.
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Notice the difference in the length of the feed lips on the magazines. The Taurus mag is on the left. It is obviously releasing the cartridge much sooner than the Mec-Gar. This alone could be causing my jams.
146158
This is from the rear. The Taurus mag is on the left. There is considerable difference in the width of the feed lips of the two magazines. I am not certain this is critical for the 40S&W cartridge, but it makes it possible to use the Mec-Gar magazine for 9mm because the lips are closer together than the Taurus mag.
The Taurus 9mm magazines I have use the same length feed lips and the Taurus 40S&W magazines but are slightly closer together than the 40S&W. Similar to the width of the Mec-Gar mags.
I am considering taking a dremel tool and shortening the feed lips on the Mec-Gar mags to match the Taurus mags and see if that is enough to make the magazines work properly.
What are your thoughts on this?

[Pee Wee]

Tasman, I had the same problem with a cz. I took a dremel and contored the back of the feed lips to go from squared of to rounded to match factory and problem solved. No more feed problems. I had the same issues as you did.

[Petrol & Powder]

My perspective would be that you do not have a functioning MEC GAR magazine now so you can't possibly break it ;) - it's already broken!
You could try cutting away some of the forward section of the feed lip or slightly modifying the feed lip by bending.
The goal is to mimic the feed angle of the functioning Taurus magazine. I think you have little to lose by attempting magazine surgery.

Once again we see the fallacy of the "one size fits all" concept. MECGAR tried to make one magazine for 9mm and 40 S&W when they should have made two different magazines

[tazman]

I have modified one of the Mec-Gar magazines by shortening the feed lips and spreading them to duplicate the Taurus magazine dimensions. I will try to get to the range and test it out in the near future.
It looks to be presenting the boolit much better now and manual feeding is good. Only shooting it will tell the story though.

[Petrol & Powder]

Good job and Good Luck !

[Petrol & Powder]

Tazman, Update please.

[tazman]

Haven't had time to go to the range yet. I have been painting remodeled rooms in my house to get it ready to sell all week. I plan to go shooting tomorrow. I will update tomorrow evening.
I really hope this "adjustment" works as I purchased 2 of those magazines.

[Petrol & Powder]

What are you doing? Trying to be a responsible adult? That's no fun :shock: !!!

[tazman]

If I get the house sold, I get to use the money to buy more guns!

[Petrol & Powder]

There you go, using logic and sound reasoning........and on a gun forum.

[tazman]

I just got back from the range. The modified magazine worked perfectly.
I loaded it completely 3 different times and it fed without any problems at all.
Now I need to do the same thing to the other one. Fortunately it only took about 10 minutes to adjust the first one so it shouldn't be a big problem.

[Petrol & Powder]

Exxxxxcellent!!!

Carry on.