TargetTalk

This came up tangentially in the thread "unique des 69 jam-o-matic fix?", but rather than hi-jack that thread, I'll start a new one.

The problem gets complicated, and I'm still trying to work with Pardini before I release my full analysis. The problem may affect other semi-auto pistols as well, but the small size of the Pardini ejection port makes it a little extra fussy.

The problem is that the nose of the 5th round can tip upward and interfere with the rearward travel of the 4th fired case. In some cases, it is bad enough that it dislodges the case from the extractor, and it fails to eject properly.

The first thing to do is to disassemble and clean the magazines. The follower is designed to tilt depending on how many rounds you have stacked up on it. Crud can build up on the front of the follower, which prevents it from tipping down as far as it should. That can leave the nose of the 5th round sticking up high enough to deflect the 4th round case.

You can check this visually if you have proper dummy rounds (not aluminum or plastic dry fire rounds), or at the range with a live round. Insert a fired case into the chamber, and close the bolt. Then insert a magazine with 1 dummy round. SLOWLY pull the slide back just until you see the case begin to deflect upward & sideways when it hits the ejection tab on the magazine. Ideally, it should never touch the nose of the dummy round. The pistol will also still work OK if it just touches, but doesn't get deflected significantly.

Here's a picture of this test on my wife's pistol when she started having problems with a particular magazine:
You can see that the fired case is being deflected quite a bit. Here's the same test, after a thorough cleaning of the magazine:
Now, the fired case is no where near the 5th round.

If that doesn't completely cure the problem, the other relatively easy "fix" is to replace the buffer. Depending on the vintage of pistol, that is either a green rubber plug in the rear of the frame, or a stack of 13 tiny O-rings in the rear of the bolt. Apparently the jolt of the bolt running into a fossilized buffer can contribute to knocking the case loose from the extractor before it is fully ejected.

Improving the grip of the extractor on the fired case can also help, but I'd start with the above two "fixes". From extensive testing, replacing the recoil spring or the magazine springs has no effect on this problem.

Try loading the fourth round fifth.

Pardini SP
I have 2 Pardini SP
They will both jam in the cooler months using CCI standard vel. ammo
Excess wax / lube on bullets
Solution is to clean off excess wax with a brush or rough towel
Keep your magazine's clean
Dennis

Looks like the cases are heavily scored especially at the mouth, so eroded chamber and reduced recoil energy are a possibility.

Don't read too much into the scratches. The test case I used was inserted & extracted dozens of times in the process of LOTS of testing. I didn't use a fresh case every time.

Thanks Gwhite!!! Can’t wait to try your ideas!

Howdy! I have had time to look at my SP, and after a thorough cleaning of the magazine...the 5th round still presents high and knocks the fired casing off of the extractor on its way rearward. Any speculation as to a fix? Thanks!!!

Pardini & I are still disagreeing on this, some vintages of pistols have design changes that I believe can aggravate the situation. However, some amount of contact with the 5th round can be tolerated if the extractor has a suitably good grip on the fired case.

I haven't had a chance to condense my notes into simple terms, but things to check:

1) Extractor grip: If you load a dummy round, remove the magazine, and open the slide with the pistol held normally (barrel horizontal), does the round stay hooked onto the bolt face, or does it fall off? If it falls off, you may need a new extractor, or you may need to stone it. I can provide details on that if you need them.

2) Extractor gap: Using feeler gauges, how much of a gap is there between the bolt face and the underside of the extractor hook? Anything over ~ 11 to 12 thousandths of an inch could be a problem. You need either a small feeler gauge set, or ones with a reduced sized (tapered) points. If the extractor gap is too large, you will need a new extractor. There is a enough variation in the dimensions that you may want to get a few to pick through, but they aren't cheap...

3) Extractor force: If you have some sort of trigger pull gauge like a spring scale or a Lyman digital gauge, you can use it to measure the extractor force. Depending on the gap under the extractor hook, you need some thin strong fishing line tied in a small loop. Hook the loop under the extractor, and clip a fired case onto the bolt face, fully seated to the rear. Then pull sideways with the gauge until the case drops. A well fitting extractor and a fresh spring should give readings around 2 pounds or more.
If it's much less than 2 pounds, you probably need a new extractor spring.

Pardini extractor springs can vary quite a bit. I think the newest ones are a good bit stronger than older ones. Here's a photo of several different new ones I had in my stash:
Some have ground ends (which I prefer), and some do not. Some are noticeably longer than others. I think Pardini USA ran out a while back, so they should have the newest design back in stock now.

4) Extractor Deflection: The extractor should move outward at least several thousandths of an inch when a fired case is clipped under it. I've seen some pistols where the hook doesn't actually touch the case. This can be fixed by careful stoning of the extractor behind the hook.

As I mentioned before, replacing the buffer can also help. If the extractor grip is a little tenuous, the jolt of hitting a fossilized buffer can jar the case loose. I'm currently trying to find time to write up a guide to replacing the O-rings in the new style bolt. I do have a write up on replacing the green buffer that goes in the frame of older SP's.

Shouldn't the case be ejected long before the slide hits the buffer?

That was what I thought, but at least with the O-ring buffer system, I've done tests that showed that fresh buffers made a big improvement in 4th round reliability. I've also spoken to another shooter who was having 4th round jams, and as soon as Pardini USA replaced his O-rings, the problem went away.

I haven't had time to figure out the exact sequence of when the ejection process starts & finishes relative to the buffer impact. I suspect the case has hit the ejector before the bolt hits the buffer, but I'm guessing the case hasn't completely freed itself from the extractor hook when the buffer comes into play. If the buffer has stiffened, there will be a sharper jolt from the initial impact than if the buffer is new & squishy.

One somewhat related and nasty quirk of this problem is that it's worse with a clean pistol. On multiple occasions, I've had students have jams in matches after having recently cleaned their pistols in preparation for the match. I've fired thousands of rounds testing various "fixes". After getting a few jams in the first hundred rounds or so after a cleaning, the frequency of jams drops dramatically. I think the fouling slows the bolt down just enough that the case doesn't get knocked completely loose. Having a fresh buffer provides enough cushioning that jams are eliminated even when the pistol is recently cleaned.

Fascinating stuff!! I got some testing to do! Thanks so much for the info because i would love to run different ammo through this great pistol. Right now, i have CCI as the sole function able ammo.

I cleaned up my notes on SP buffer O-ring replacement. It was too large to just attach, so I had to park it on-line & set up a sharable link:

https://drive.google.com/file/d/166gGpD ... 0HSvn/view

a great write up - thankyou!

Thank you for the excellent tutorial on the O-ring replacements. My Pardini is 6 years old and probably 30,000 to 40,000 rounds. I never even concerned myself about the buffer until this thread came up. $62 is quite the rip-off for small O-rings. What are the dimensions of each ring?

Secondly has anyone tried a spring in place of the O-rings?

Brad

Depending on the tariffs, they may be cheaper in Canada.

I was also initially appalled at the price, because standard small O-rings are about 5 cents a piece. Pardini USA explained that they are a special material, and that a lot of the cost is the per-piece import tariff on ANY gun part. If the US government slaps a $2.50 tax (that's a guess) on every part, the cost is going to be out of whack. I'm not sure if Pardini can do this (or are already doing it), but it seems to me that if they imported all 13 O-rings in a set as a "buffer", they might be able to get the tariff applied once instead of 13 times.

As best I can tell, the O-rings are ~ 5.4 mm OD. Given that a stack of 13 measures ~ 24 mm, the cross-section would be ~ 1.85 mm. There are DIN O-rings that have a 1.8 mm cross section, and that would give a stack length of 23.4 mm, which is close. A 1.8 mm cross section and a 5.4 mm OD works out to 1.8 mm ID. The very smallest DIN 3771 standard O-ring is a 1.8mm X 1.8 mm size, so I'm guessing that's it. The is also an ISO 3601-004 O-ring, which is 1.78x1.78. The size I measured is within the tolerance range of both specs, but the DIN appears to be closer to what I measured. Either size is scarce in the US.

The trick is the material. Buna N nitrile is the most common (and cheapest) O-ring material, but it comes in different stiffnesses (Shore D "Durometer" hardness). The most common is Durometer 70, and that is used in a lot of air gun applications. Sometimes higher pressures require Durometer 90. There are dozens of other materials used in O-rings, and they can also be had in different hardness ratings.

Given that the buffer O-rings are being used as a "damper", even hardness alone isn't the whole story. Short of sending some of the O-rings off to a laboratory, there's no telling what they might be.

I certainly don't want to risk cracking the aluminum frame of a $2000 pistol over the price of the O-rings. If you lubricate them well and replace them every 6 years to avoid that, it works out to ~ $10 a year. Even if you have to replace them every 3 years to avoid malfunctions, it's less than the cost of a brick of ammo per year.

There are other things one can do to reduce the 4th round jam problem. If the pistol worked well when new and the magazines are clean, there are only two likely suspects for something that changed over time: 1) the buffer, and 2) the extractor spring.

Greetings,

Looking at McMaster-Carr website, I find several material options for a -004 O-Ring.

It would be worth a trip to a specialty shop that "knows" O-Rings to determine at least the Durometer of one. Perhaps the O-Ring expert can identify the material, as well.

Many times it is good to consult with the "Experienced Guy/Gal".

Cheers,

Dave

Actually my Pardini functions just fine. Only 2 or 3 malfunctions in 30K rounds, all with Federal ammo.

I was just thinking ahead re: future maintainence as I plan to shoot the gun until they scatter my ashes at the range one day. As well I end up being Mr.Fixit for the few high end guns in my neck of the woods, The only remaining gunsmiths in Western Canada have no clue what a Pardini or Matchgun or any Olympic style gun is. So I end up with all sorts of intersting stuff to fix.

Thanks for all the time and effort you've put into this, it's really helpful

Brad

fc60 wrote: ↑Fri Jul 26, 2019 7:41 pm
Looking at McMaster-Carr website, I find several material options for a -004 O-Ring.

You have to be careful. McMaster Carr's "dash numbers" refer to SAE standard AS568 numbers. The ISO (metric) standard -004 size I mentioned are very different. The material options will be similar.

Greetings,

True, the McMaster are listed as Inch o-rings.

I did convert the -004 o-ring to Metric values and they lined up.

0.070" cross section = 1.78mm

0.070" inside diameter = 1.78mm

A sample offering...

https://www.mcmaster.com/9557k61

Cheers,

Dave

Nicely done! I don't know what I didn't find that one earlier... English O-ring sizes are a bit weird, and I may have gone by the 1/16" rating, which would be too small.

The -004 size might work if the right material can be figured out. That size is available in 9 different materials, and six different Durometer ratings.