Got a newer SP22 and metric calipers? Help with a project!

I have an SP22 that has the newer style bolt frame, but does not have the shock absorber system.  An updated bolt frame is a billion dollars from Pardini.  I figured I could order the shock absorber parts and machine the two holes needed.

I have the shock plunger, damper pin, and o-ring set on hand now.

What I don’t have are the locations and dimensions of the holes.  So, I am asking anyone with the newer bolt frame style, a good set of calipers, AND knowledge of how to properly use those calipers to take some measurements from your bolt frame.  

Also, this pistol is built in metric and I am using metric dimensions to avoid conversion errors.  Sorry, your tape measure will not cut it.  I want dimensions to the nearest 0.05mm or better.  Yeah, there is gonna be some fudging and my bolt frame dimensions may be different than yours because someone spent too long sanding in one spot, etc. We are just gonna work with it and see what we get.  I’ll take measurements from as many folks as want to supply them and average them all out!

Here is what I need as seen in the CAD drawings.

A1 and A2: This will give the center of the damper pin hole.  You can also just measure from the bolt frame edge to the inside of the pin hole in both directions and I can get the center point from that.

B: The distance the plunger sticks out of the bolt frame.  This will actually help confirm the location of the damper pin, as it rests against a ledge on the plunger.

C: This is the depth of the hole for the plunger and o-rings.  I am not sure if this hole has a flat milled or a pointed drilled bottom, so make sure to measure at the edge of the hole, not the center, if it is drilled to a point.

D1 and D2:  Similar to A1/A2.  The center point is great, but if you can get me the distance from the outside of the frame to the closest edge of the hole, I can use my software to get the hole center location.

When or if this all works out, I will repost instructions so other folks can attempt this conversion themsleves.

from my Pardini SP RF 2018 model with buffer & pins in place and by my eyes - caveat emptor

A1 = 5.30 to 5.40 mm
A2 = 5.90 to 6.00 mm
  B = 4.40 to 4.50 mm
D1 = 5.50 mm
D2 = 3.00 mm

Thank you!  I will get this plugged into my drawing and see how it works out.

I still need dimension C, the depth of the hole, if someone can supply it.  You will have to knock out a pin to release the plunger and o-rings, but it is not hard to take apart and reassemble.

Will

dino911 wrote:from my Pardini SP RF 2018 model with buffer & pins in place and by my eyes - caveat emptor

A1 = 5.30 to 5.40 mm
A2 = 5.90 to 6.00 mm
  B = 4.40 to 4.50 mm
D1 = 5.50 mm
D2 = 3.00 mm

I have cross checked with my CAD model and your measurements are very close to what I had initially laid out.  With these dimensions, you supplied the fine tuning to give me exactly what I needed.  Here is what I have settled on based on what the CAD model says will work.

A1 = 5.30 mm, not much more than this or you risk drilling into the firing pin channel.
A2 = 6.00 mm
  B = 4.50 mm
  C = 32 mm
D1 = 5.75 mm
D2 = 3.25 mm

sorry, don't have a pin punch to knock the pin out

this might help ?
https://www.youtube.com/watch?v=0sLJzAhYA-Q

Dino911, I have watched that video, but am glad you called my attention to it again because I was able to notice a minor detail.

There is no pressure applied to the damper in order to remove or insert the pin.  This would imply there is no preload on the damper.  This lends a bit more to the 34.5 mm depth measurement that works for my parts.

Dino911, does your damper plunger feel loose, tight, or just right?  Yeah, it may not be the same as it was when brand new, but just want to get an idea of the fit.

Thanks for your help!

Hi Will, my Pardini has had less than 500 rounds through it and I would say the damper/plunger is between just right and tight, there is no play in and out and with a little force it can be compressed slightly....hope this helps

Yep, it helps!

I am gonna lean towards 34mm depth for C.  This gives .5mm compression, just enough to keep it from being loose.

Would still like a measured dimension for confirmation of that depth.  Maybe someone can come through on it.

pics of the project please

Who would have thought that it would take so long to get some drill bits?  Covid related shipping delays, so I am still waiting.

In the meantime, I did a test with my 3d printer to see if I could nail down a depth for the shock damper hole.  Dino911 sent me a PM saying he got the pin out and even though he could not measure the depth of the hole, his damper had to be compressed in about 2mm to allow the pin to be inserted.  Based on his measurements and mine that puts the depth between 32-34mm

So I made up a print that has holes at 32, 33, and 34 mm depths.  I tried them all out and 33-32mm is definitely it.   The print has flat bottom holes, but the final drilled hole will have a small divot, so I going to say 32mm measured at the edge of the drill or 33mm measured from the point.  I will update the post a few up from this one with the new dimensions.

I even did some compression tests of the damper by hand and using a postal scale at each hole depth.  A 1mm difference in depth makes no difference in the feel.  This measurement has some tolerance to it.  If I need it any deeper, I can always drill a hair more.

Now I am just going to have to be patient and wait for my tooling.

Well, this has been an interesting project.  I had some unusual shipping issues (parts sent to Texas and Covid delays).  Then I had to reorder drill bits twice to get the right size.  I broke my milling machine.  I lost two of the pins (ordered more and found one of them laying right in front of me while unpacking the new parts). I also took on a few other projects, so yes, there have been some delays.

Here is where I last left the bolt frame.  I guess this is the “Before” pic.  I even made a quick and dirty test piece which I drilled first to check my dimensions and part fitment.  Then I machined the actual bolt frame. The blue dye is to help mark where the new holes will be.

I am not one to do much product endorsement, but I ordered some specially hardened metric drill bits to do this job.  There was a shipping delay, so I contacted the company to ask about the shipping status and got an email from the owner, Brendan.

He told me he was sorry about the delays AND let me know he was refunding my money AND he was sending me my order anyway for free AND he was including a package of their paste lube, safety glasses (with pouch) and a pen!  

I really did not know what to say, but was so impressed that I have to give TTP Drills a shout out for the amazing service.

It turns out the drill bits and paste lube worked great!  Nice!

https://www.ttp-hard-drills.net/ and they are on Amazon as well.

SO, I finally got it all together and the Pardini is working and cycling ammo at the bench, but have not taken it out for a live fire test.  I feel pretty good about it working as planned.  I’ll follow up soon.

As for the job itself, it is NOT one for a noob with a hand drill. You need some precise tools and some experience using them.  You can very easily screw this up, maybe even ruining your bolt frame.

  This is not just drilling two holes in a hunk of metal. They have to be in EXACTLY the right place and you get one shot and you only know the first hole is right after the second hole is drilled.

Measure twice and twice more and THEN cut once.  

Here it is, new shock damper system installed!

As promised here are the final dimensions, along with the tooling, and parts needed.  You should be using a milling machine for maximum precision.

Drill bits: 5.5mm and 1.95mm  Only use high quality bits.  A good bit is cheap compared to the cost of a new pistol bolt frame!  I ordered the 5.5mm hardened bit from TTP Drills, as seen in the post above.  I ordered 1.95mm hardened bits from MSC Industrial Supply because TTP did not stock that size.

Parts:  Ordered from Pardini USA.  
770 -SP Shock Damper Rod
771/13 -SP Damper O’Ring set (13 pieces)
769 -SP Damper Locking Pin (can also use part 708, it is the same size pin)

Dimension Drawing (mm):  Fair warning folks.  These dimensions worked for me and my parts, they may not work for you.  Use them as suggestions only.  Prepare for some hand fitting for best operation.

Also, big shout out to dino911.  He really came through for me on those initial dimensions.  

Teamwork makes the dream work.

THANK YOU DEAN! 

Great work Will - it's nice to see a project go to a successful completion !
Now if only you were closer to me..... I have a little job on my Pardini that needs doing

regards
Dean

Will, that looks great!  How much would you charge to do this conversion with customer supplied parts?

$1,000,000.00 Willie!    I still have my 07 FFL, but am not currently taking in work.  I am releasing this info for anyone to use at home or in their own pistol shop.  

***

Just to further update, the pistol shoots fine with the new shock system!  I did have to make one more modification to the bolt frame and here are the details.  That should wrap this project up and the pistol is good to go!

The issue was that once the new shock damper was installed, you could not shove the bolt frame back far enough to allow the  stop button to rise up and hold back the bolt.  (You can REALLY shove back the bolt, but the damper does not compress that easily)  It almost works, but I wanted to get it working effortlessly. (I am wondering if the bolt frame length or pistol frame depth or bolt stop button location may be different on the pistols which have the modern bolt frame.)

The solution was to mill a small pocket at the front of the bolt frame to allow it to pull back far enough to engage and disengage the bolt stop button properly.  

The pocket I made was large enough to receive the pin with a fully assembled pistol AND it is large enough to hold the bolt back with the barrel assembly removed.  The assembled pistol forces the bolt frame to travel a path constrained by the barrel, but with the barrel removed, the bolt frame can jiggle around in the frame quite a bit.  By making this pocket a bit larger than the stop, the bolt will engage the stop button, no matter how the sloppy alignment is when the pistol is apart.  This is a really small little detail, but is one of those things that is just a nice touch for the owner.

Non SP22 owners are now like, WTF is he talking about?  

-Machining Details-

Tooling: 
0.125” 4-flute AlTiN coated end mill is what I had on hand, so I used it.

Pocket size: 
0.060” deep from top dead center of the bolt frame 
0.125” length from the front edge of the bolt frame 
0.185” width across top dead center of the bolt 

*As stated in other dimension references, these worked for my pistol, yours may be different*

You can see the bolt frame pocket cut at the front of the bolt: