Setting Headspace on Pardini PGP 75 Free Pistols?

[Gwhite]

The MIT collegiate team has about a half dozen of these pistols. They have seen a lot of use, and several of them have issues that could be corrected if I knew how to set up the headspace. I have all the parts we might need.

The headspace in the PGP is set by an eccentric bushing that is held in place by the bolt handle, which screws down on the bushing. The forward location of the bolt is determined by the bushing seating into the bolt slot in the frame. If the thick part of the bushing is rotated to be towards the back of the bolt, it locates the bolt further forward. If the thin part is towards the back, the face of the bolt is located further back, increasing the headspace.

There are two issues I need to figure out before I tackle these pistols:

1) The bolt handle is tapered, with no flats to grab. If you don't want the bushing to rotate, it has to be clamped pretty well by the bolt handle. I also don't know if they used any threadlocker on these things. So, I need a good way to grab the bolt handle securely, both to get it off, and to crank it back on nice & tight. Short of making some sort of custom fitted clamping gadget, the only thing I can think of that might work is a small strap wrench.

2) I need a procedure, and possible a go/no-go headspace gauge of some sort, to actually set the headspace. One of the pistols has a cracked bushing, and one has a bushing that has slipped. Both suffer from unreliable ignition. I can measure all the critical distances carefully, and try to set the headspace to match the pistols that work OK. Or, I can try to rotate the bushing temporarily long enough to test fire the pistols.

I contacted Pardini USA, and because these pistols predate the US company by a couple decades, they don't know how to do this. They asked the factory, and they couldn't/wouldn't provide any useful info.

So, does anyone have any experience or suggestions on how best to proceed?

Thanks!

[tqb]

I don't now if this helps.

I had some ignitions problems with Eley Match ammo, the firing pin just didn't dent the rim enough for the ammunition to fire.
It still worked with other ammo, that had thicker rims, such as the Eley club.
I replace the firing pin spring and that fixed my problem.

Regarding headspace, unfortunately, I can't help.

TQB

[Gwhite]

Some of the marginal pistols can work with selected ammo types. We had one that only worked reliably with one of four types we tried. Another issue is that the PGP's have VERY tight chambers, and a lot of ammo won't extract well unless the chamber is spotless. Some ammo is tight even then.

I talked with Larry Carter at Larry's Guns, and he said he's fixed a number of PGP's, but the headspace is largely set by trial & error. I have some ideas about ways to make it a bit more deterministic, and will probably work on it over the holidays when the team is inactive. I can make go/no-go headspace gauges out of brass, and I think feeling the difference can be aided by removing the firing pin & extractor first.

I'm not sure how tight the bolt handles are screwed on, and Larry said he used thread locking compound when he reassembled them. I'm not sure if the factory did, but if so, I will have to heat things to soften that up. I have a small strap wrench (somewhere...) that might work well on the tapered bolt handles, but I'm not sure how much heat the strap can take.

[Greg Derr]

Headspace on a Rimfire? If the rounds are tight, it's not an issue with headspace, the bolt closing will seat the rounds and start to engrave the LANs and grooves on the soft lead. Your issue is with ignition? The rounds are not getting the full strike from the firing pin, and or are only being seated by the FP strike. The FP spring needs to be replaced. Much of the domestic ammo and some from south of the border today are either over waxed or out of SAAMI spec. Function issues as of late with Rimfire has been spotty as higher production rates have taken a toll on QC. Invest in a SAAMI spec set of GO, No Go gauges if you can, brass deforms too easily to be used over any period of time. You can also have the barrel shoulder cut, rechambered and the extractor groove lengthened if you get throat erosion .

Damn autocorrect!

[SamEEE]

Out of curiousity did you check the firing pin springs?

Try a known good firing spring in a dodgy gun and see if it makes a difference.

We have one down here in my club which has spotty ignition even when fastidiously clean - perhaps together a bit of knowledge could go a long way.

[Gwhite]

The one pistol I've worked on most recently has been thoroughly cleaned, lubricated, and a new spring installed. I forget which ammo worked, but we tried 3 or 4, and it still misfires occasionally.

The headspace is set by an eccentric bushing held on by the screw-on bolt knob. The bushing is what holds the bolt against the frame at the back, and depending on how the bushing is rotated, it moves the face of the bolt back & forth relative to the breech face.

We have two pistols where the bushing is split, one where the bolt handle came loose & the bushing is free to spin, and one where the bushing is worn down a bit. That's the one that is fussy about ammo. The other three are out of service until I can replace the bushings and try to set the headspace.

The headspace for match rimfire should be about 0.043". I can buy or make a gauge, but setting the bushing rotation & then locking it down is the process I need to develop. On a bolt action rifle, you would adjust things until you can just close the bolt on a "go" gauge. I think the same process can be followed with the Pardini, except you need to keep track of the bushing orientation with an index mark, and then fuss with it until it just closes on the gauge. In theory, you then just need to add some threadlocker, and crank the bolt handle on while ensuring the bushing doesn't slip.

[j o danielsson]

I had a k50 once, same bad construction. You need to get that eccentric bushing tight or the recoil will smash it. In time it will go half semi. Throw out the empties by itself. If it ignites.
You need a lathe, or a simple drilling machine and a file, to make new round bushings slightly oversized. Make a lot, wear them in, change often.
Yes, there is some glue in the threads of the handle.

[SamEEE]

I did a few thought experiments with this one

The handle acts as the cam/locking surface from memory - maybe that has also worn. Between the sleeve/bolt/handle there is the potential for 3 wear points.




Sounds like a new bushing might be the go - you could try my method if you're feeling extra agricultural.

Seeing you have 5 why not do some measuring of a good one vs. a bad one and get some proof of specs? Some machine plans for a new one would be a good resource!

[Gwhite]

I took a bunch of measurements a while ago, but I need to go over them carefully again. Shimming as you suggest would be tricky, because the rear extractor pin sticks out the back & pushes against the bolt handle to provide a bit of a detent when the bolt handle is locked upwards. This is one of the things that makes measuring tricky. You have to compress things in order to get a valid measurement, OR you have to take the bolt completely apart to take out all the springs. The good news is that disassembling the bolt is pretty simple once you have the hang of it.

Four of the pistols have either split, worn, or loose bushings, so I need to rebuild those no matter what, and I have all the parts I need. Hopefully I can work up a procedure that allows setting the headspace reliably without too much fuss.