Canadian Airgun Forum

Diana Model 52 quick tune
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Author:  riflerick [ Tue Apr 19, 2016 11:17 am ]
Post subject:  Diana Model 52 quick tune

I recently came into possession of a nice condition model 52. In .177
Paid $350 cdn. for it, a little risky as I did not fire it, but its a gun I have wanted for a while.
The owner bought it in Germany and shipped it here when he moved here. So he said anyway.
He had made a wooden case for it for protection.
Excited to try it out I went home and pushed a bit of lead through it. It seems fairly punchy with lots of expected spring slap.
Accuracy was not bad. at 30yds keeping it in the black, with a few erratic's.
I put it up on the Chrony using Crossman wadcutters and it was recording an avg. of about 736 fps. quite disappointing at this point. there was also a 85fps max deviation, I partially blame this on the ammo.
Tried using match grade wadcutters and the result was very similar.
I then tried Crossman prem hp's and had a better result as far as deviation is concerned but FPS was still low IMO.
All along I have been experiencing a fair bit of dieseling.

So we all know what happens next :D
On the bench it goes.
I will keep this as short as possible and if there any questions at the end please send em along.
I will add a link to pics at the end.

My first tear down of one of these, but it went smoothly, I had a parts diagram handy to make it easier.
For the most part one of the better made guns I have worked on in a while as far as fit/finish/clean manufacturing etc.
One of the first things I noticed as I remove the stock is an abundance of a sand like substance all over the place.
This made me very nervous thinking about what may have happened inside.

Pull the trigger assembly with the end cap off and release the spring. No sign of sand inside, but lots of heavy grease and abundance of oil. The trigger assembly had some sand on it mostly on the outside surfaces.
Spring and piston tube looked healthy, seal was a little fuzzy around the edge, but nothing I have not seen before and rectified.
I did notice some linear scoring in the air chamber but nothing too scary, maybe causing some minor blow by.
I did a complete cleaning, removing all this sandy stuff from everything.
There was a fair bit of grease all over as well, looking to me like the gun was hardly used and this is all original lubrication.
Everything cleaned, I may as well do some minor improvements going back together.

Looking at the spring under 15X mag I could still see some spurs but it was looking pretty good.
I gave it a quick polish in and out just to make sure there is no interference.

The guide was in good shape, but a small injection spot that was raised, so I smoothened this out with some fine emery as well.
I decided to spice it up a little and quiet the slap, so I turned a 1/4" UHMW washer/spacer for the other end of the spring in the piston tube.
I polished the fuzzies off the seal using Tripoli polish and a cotton wheel. this works if your careful.
I quickly honed the air cylinder to remove some of the linear marks using a custom cylinder hone, then cleaned this up with a custom hard felt wheel impregnated with green honing compound attached to a dowel and turned using a cordless drill. (This is my normal process for air chambers for the past few years)
I deburr the edge of the air chamber as it was sharp, just to make the piston install easier and to not harm it.
The outside of the air chamber is a little scuffed and I clean this up with fine emery, 15u I believe.
Very lightly apply moly on the spring and forward moving parts.
A tiny bit of synthetic oil on the fingers wiped on the seal then basically wiped off so only a micro amount remains.
Up on the spring compressor and install spring and press trigger block with end cap into alignment.
It is important to note that the safety lever spring clip is positioned in one of the dowel pin holes in the trigger assembly and the safety should be pushed forward to make the second pin go in easier. hopefully you can see this in the pics.
All back together and back outside to burn off the small amount of lube.
First cocking, I noticed that it was jut barely catching, indicating that the 1/4" spacer was pushing it.
I put about 25-30 pellets through it and feel a smoother spring slap, but still have the beast of a spring recoil I am expecting.
I put 5 rounds into the target on a rest, with all 5 touching each other at 30yds.
The cocking became a little safer feeling at this point.
Happy with this I place it back on the chrony.
Using CPHP's again, I am now averaging 1014fps with a max deviation of 32fps. I'm very happy with this using these pellets on this much power.
I then did a selected pellet test and pressed the skirt on my brass skirt former and got a much better 24fps deviation while maintaining a 1006 fps avg.
I go back outside and place a pop can about 70 yrds out. and hit it 9 out of 10 times free holding with a basic swiss arms scope.
I also noticed after the scope had slid back on the rails due to recoil and I had to move it forward again and tighten up more.
Also the foresight slid back as well, but I removed this as its not needed with a scope anyway.
This result is not typical of course of a tune or any rebuild, and I am still not sure why it was so slow in the first place, maybe the excess grease or the dieseling or the fuzzy seal. I don't think it was the sandy stuff, but maybe a factor.
Either way I now got another gun that sits on top of my list of long range plinkers and have since put a couple of hundred pellets through it and loving it. My arm is sore and not used to the side lever :D
I may put a Vortek kit in it later to see if this helps smoothen out the stroke.
Anyway any questions ,please feel free to ask.
Photo link may have to be copied and pasted. ... t=3&page=1

Author:  Ace [ Tue Apr 19, 2016 11:33 am ]
Post subject:  Re: Diana Model 52 quick tune

good job.... 8)

Author:  riflerick [ Tue Apr 19, 2016 4:05 pm ]
Post subject:  Re: Diana Model 52 quick tune


Author:  dyslexic_nam [ Tue Apr 19, 2016 9:37 pm ]
Post subject:  Re: Diana Model 52 quick tune

For those of us not used to tuning springers, it is helpful to have that kind of walk through. Great info on the step-by-step process. Cheers

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