Pardini K12 - low velocity

[Brian James]

My Pardini K12 is shooting slow. Using a chronograph (Garmin) it is shooting around 108mps or 350fps with H&N final match and slower with RWS R10. Other quality air pistols using the same chronograph during the same testing session are shooting around 158mps or 490fps.

Observation: The screw MP is fully screwed into the frame. When it is loosened the velocity decreases to 80mps or 260 fps.

While it is hard to diagnose a problem sight unseen, I’m wondering if anyone has had a similar issue. The firing pin spring is intact, but slightly curved. Not sure if a new spring or stronger spring would make a difference.

Thank you in advance

Brian

[Gwhite]

If the striker system is cranked in all the way, that suggests that the regulator isn't putting out enough air pressure. I have no idea what is involved in rebuilding the K12 regulator, but I've fixed quite a few Hammerli 480K's and a couple Steyrs with low velocity by replacing the pressure regulator piston seals.

[David M]

A038-A044-Complete-and-Spring-Reducer-Set.jpg (51.05 KiB) Viewed 16798 times

The Pardini K12 pressure regulator uses a spring pile of 6 Belleville Spring Washer's back to back.
The easy way is to replace the pressure regulator, the hard way is to find the replacement
Belleville Spring Washer's of the right size.
You could also replace the striker spring.
Then set your velocity at somewhere in the range of 480 to 530fps.
The Italian's arn't know for the worlds best springs.

[Gwhite]

Belleville washers typically can't flex far enough to lose compression. I've rebuilt a bunch of Benelli Kite regulators, and I re-used the Belleville springs. The velocity generally comes up pretty close to where it's supposed to be.

I've rebuilt over 20 Hammerli AP40 regulators, and reused the coil springs. All they needed to get pretty close to the nominal velocity was replacement of the piston seal. I think what happens is the seals wear (or in many cases, start to disintegrate), which reduces the friction. That makes it easier for the piston to move, which results in the regulator valve closing at a lower pressure than desired.

[thirdwheel]

Brian don't start pulling it all to bits and worrying - do the simple tings first - change the spring as all springs will slowly take set over time especially if left cocked in the case for long periods. When you have put in the new spring monitor the speed for a while. My Spring lived good and strong for over 10 years of constant use but suddenly died, as you know simple job to deal with.

[Brian James]

Thank you all for the advice and guidance. I’m trying to find a new spring locally while searching for a source of seals and costing out a regulator.

[thirdwheel]

Brian leave the regulator alone just get hold of a spring and see if that cures it - my money is on it will cure it, don't mess about trying to find a spring of unknown power, order one from the importer in Canada of if that fails Pardini USA as they have them in stock - one is on the way from them to me at the moment. Just use your pistol as it is as it will not harm it or your scores and change it over when you get it. The pardini reg is not adjustable unlike other it is simple and it just works, The Brelliville washers rarely give up as Gwhite has mentioned so don't chase some down, later if you find the spring does not do the job I will talk you through the simple process of checking out the area down there. Don't worry!

[thirdwheel]

To keep you out of mischief till the spring arrives there are some other things to check for low velocity.
1 Is the O ring in the nose of the sliding breech still there or has it been shot down the range, because I've done it when the breech has not been closed properly but I did see it fall out, I always keep a couple in my shooting case.
2 Is the breech seal sealing on the end of the barrel to check for air leakage drape a light piece of tissue paper over the area to see if it moves when you fire, if it is leaking replace the O ring or move the barrel rearward a tad so it engages more. To do this release the barrel by loosening the two crews on the frame which clamps the barrel, hold back of pistol against your body and gently pull the barrel rearwards to engage with the closed bolt then tighten screws - don't over do it. You need to use some mechanical sympathy now - open and close the cocking lever - is too much pressure now needed to get that "click" if so back off the barrel a bit.
3 Is the transfer seal under the bolt still doing it's job to check close it on a 1 thou feeler gauge if O ring grips it tightly all is good if not you need to either use a new O ring or engage the barrel in the bolt rearward a little more.

If you need to take the sliding bolt out to change the O ring DON'T undo the very little screw that connects the cocking lever to the bolt, instead remove the cocking lever pivot screw ( it is tread locked so will be stiff) and then remove the rear sight and slide the bolt and cocking lever together rearward out of the frame.

[Brian James]

Good news update

I replaced the firing pin spring with a generic coil spring nearly identical in size to the factory spring that my local gunsmith had on hand. Not it shoots consistently 480fps. I also inspected the o-rings and they are all present and appear to be in good shape.

I’m still going to order a replacement spring from Pardini.

Side note: This issue with the Pardini forced me to pull my old Matchguns MG1 in preparation for a regional match today. Besides bring a little heavy the MG pistol have really nice rear sights.

[thirdwheel]

Splendid and phew!
It is really hit and miss trying to advise remotely and is the way of madness at times.
Any new spring takes a while to find it's happy place so monitor it and adjust as needed until it settles.
Only had a MG1 in my hand a couple of times but have no memory of the rear sight, what does it do better than the K12's, hope the match went ok.