Pardini SP 4th Round Jams

[fc60]

Greetings,

The quest begins.

McMaster list what chemicals the o-rings are compatible with. Since we deal with gun oil, Hoppe's solvent, and cleaning solutions many of the materials can be eliminated.

The Durometer would be the next challenge. I have a Durometer tester; but, I cannot figure out how I would test one of those little o-rings. This is where a trip to the Industrial Supplier would pay off. The "experienced guy" would likely squeeze it between thumb and finger and declare it's hardness.

Viton is a popular material in Europe for o-rings. I would likely start researching this material first.

Cheers,

Dave

[Gwhite]

The nice thing about Viton is that it's very resistant to all sorts of chemicals, and it might last even longer than whatever Pardini is using. I think we can eliminate Kalrez as a material. Those cost ~$28 and up per O-ring...

"Abrasion-Resistant Polyurethane" O-Rings might be good, but they cost $2.87 a piece. Maybe that is what Pardini is using, in which case their prices aren't so unreasonable.

As I mentioned, the hardness isn't the whole story. What you want to also know is how well it absorbs energy. I've been mulling over how to make a sliding weight that you could drop on an O-ring & see how high the weight bounces.

McMaster lists a "super resilient" Viton that could be good, but it might actually be too "bouncy".

[hurt]

Tried the trigger pull gauge on the fishing line...1.1 lbs, so i will try a new spring!!

[Dipnet]

I had a mystery FTF that appeared after many thousands of rounds and it typically affected the second, sometimes third round in magazine. I tried replacing magazine springs (during the time when Pardini USA did not have said springs in stock, so I used other 22 pistol mag springs [High Standard replacement springs, I think]). However, new springs didn't correct problem. Rats, big ones.

It turned out to be a small burr on the edge of the magazine thumb slide slot; a small flat file took care of the problem. I've subsequently dressed all the thumb slide slots on other mags and found one other burr. I am now burr-less.

It is still a mystery why it did not the FTF didn't occur earlier.

Regarding the recoil dampening rod (and the 13 O-rings) in the Bullseye SP; I got rid of them and rely exclusively on the green dampening buffer. I did this because the recoil dampening rod actually damaged the green buffer (after may be 5K rounds). I spoke to Alex about it and he said that was OK, but cautioned that I should check the green buffer pad regularly to make sure it's undamaged from wear. Attached image shows damage cause by the recoil dampener in the Bullseye SP model. dipnet

[Gwhite]

I'm confused... It may be the bullseye model, but I didn't think pistols with the buffer rod & O-rings in the bolt used the green buffer. Unfortunately, the newer SP's I work with that have the buffer in the bolt are in lock-down still, and I can't check them.

[j danielsson]

I think they put together whatever they had for a while.
The green buffer is gone now.
Their quality was real poor the last years. Often they did not last a box of Lapua.
I have glued a 2.5 mm thick piece of softer rubber on them. Works, but what kind of glue is tricky. I will try just a dab of the glue gun next.

[gfrad1]

I had same problem I replaced extractor on my pardini sp no more jams

[Gwhite]

If your extractor has a really good grip on the fired cases, that will help a lot. If the 5th round is popping up enough to hit the 4th round fired case, it may still loose its grip and jam occasionally, but it will be much less frequent.

One thing to watch out for is that the extractor spring is a bit overstressed. They will compress over time, and the grip will get weaker.