Diana Diana 54 air king pro 7.5J

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Hobbyman2007

Hobbyman2007

Member
Nov 17, 2015
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Ontario, Canada
I have a 7.5 J coming and I’d like to see if anyone has ever converted one to full power. From the very little information out there about the low power versions it looks like there’s more than likely a transfer port restriction in the form of a washer with a tiny hole ( 2mm or less) as an air passage and more than likely a weak spring in there. I’d like to hear first hand from someone that has gone down this road before.
I did send Hector an email asking about a short stroke piston but he didn’t seem certain as Diana uses all kinds of different methods to detune their rifles.
I have a Maccari spring , piston and breech seal coming from ARH and hoping I’m not missing anything.
I’d really like to get this rifle shooting close to 20 FPE as long as it likes the 10.3 JSB pellets.
This one came up on sale , brand new for 550$ snow pesos ( canadian dollar ) which I thought was a very good deal, considering there are some vendors still asking 1100$ for exact same rifle. So even after the extra parts and a bit of time I think I’m still way ahead ( if that even makes sense)


I was supposed to be downsizing my collection. Throw that plan right out the window. 😂
 
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Hobbyman2007 said:
I have a 7.5 J coming and I’d like to see if anyone has ever converted one to full power. From the very little information out there about the low power versions it looks like there’s more than likely a transfer port restriction in the form of a washer with a tiny hole ( 2mm or less) as an air passage and more than likely a weak spring in there. I’d like to hear first hand from someone that has gone down this road before.
I did send Hector an email asking about a short stroke piston but he didn’t seem certain as Diana uses all kinds of different methods to detune their rifles.
I have a Maccari spring , piston and breech seal coming from ARH and hoping I’m not missing anything.
I’d really like to get this rifle shooting close to 20 FPE as long as it likes the 10.3 JSB pellets.
This one came up on sale , brand new for 550$ snow pesos ( canadian dollar ) which I thought was a very good deal, considering there are some vendors still asking 1100$ for exact same rifle. So even after the extra parts and a bit of time I think I’m still way ahead ( if that even makes sense)


I was supposed to be downsizing my collection. Throw that plan right out the window. 😂
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While your at it call Hector back and get a tuner from him. It cut my groups from a tuned 54 in half and that's with 15.89 JSB at 760 fps.
 
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JEFFPPC said:
While your at it call Hector back and get a tuner from him. It cut my groups from a tuned 54 in half and that's with 15.89 JSB at 760 fps.
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I’ll be calling him once I get the rifle tore down and take some measurements. I do have a couple air strippers from different suppliers , and they do improve groups a bit. Knifemaker ( who I haven’t heard of in a few years ) and I worked on some vibration dampeners a while back. I still use them on a couple of my high power slug shooters. Think dead blow hammer.
 
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he drives me nut as a presenter, but he does have some interesting products
the idea that you could respring a 48-52-54 to full power and not need a spring compressor is an appealing idea
i made a comment on a UK forum about using a magnetic dish for the parts, he tends to scatter them around and i was watching a video and he made an effort to point out he got one and was using it

good luck with your rebuild
mike
 
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marflow 777 said:
he drives me nut as a presenter, but he does have some interesting products
the idea that you could respring a 48-52-54 to full power and not need a spring compressor is an appealing idea
i made a comment on a UK forum about using a magnetic dish for the parts, he tends to scatter them around and i was watching a video and he made an effort to point out he got one and was using it

good luck with your rebuild
mike
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One of his spring guides gave way on my HW80 Wouldn't use his kits
 
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marflow 777 said:
he drives me nut as a presenter, but he does have some interesting products
the idea that you could respring a 48-52-54 to full power and not need a spring compressor is an appealing idea
i made a comment on a UK forum about using a magnetic dish for the parts, he tends to scatter them around and i was watching a video and he made an effort to point out he got one and was using it

good luck with your rebuild
mike
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That’s funny. Many years of racing slots and RC cars taught me to use those. I also have a mat, kind of like a large mouse pad, that’s very handy.
 
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small parts disappear we have all lost something an spent 30 minutes looking and then find it and wonder how the hell did it get over there and many of these parts are not available and if they are, will cost you 10 bucks to replace
i just fixed 5 Ruger MK ll because they would not cock and i use stick magnets for the small parts
no matter how hard you try you will lose a part
 
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I finally got the rifle. I haven’t received my ARH order yet but tracking says it’s in Canada.
I didn’t even fire a single pellet and tore into it. Tear down is relatively easy. What I found inside the rifle is quite surprising. No a lick of lube on the piston , compression tube or otherwise. The trigger does have some of that thick ( lithium grease ? ) white stuff in there. There is some preload on the spring. Measurements are , 34 coils, .80” OD .115 “ wire thickness and an overall length of 10 7/8” . Inside the compression tube , behind the ( damaged from factory) breech seal is a restrictive washer, just like in the video. When I pulled the piston and comp tube assembly out. There is a small black colored washer. Which I’m not sure where it goes. I’ll have to look at the breakdown to figure that one out. So by the looks of it, the only thing done to detune these rifles is the restrictor. WOW. This must have shot like $hi+.
While I’m waiting for my order , I’ll take care of the sled, polish all parts up, install the front sight and get the rest of the parts cleaned up.

Overall this is much better than the one and only other Diana rifle I’ve owned. I will say that the use of this much plastic on a Springer does not scream “ high end” but it’s not the cheap stuff either. Let’s hope it’s a shooter.

IMG_1117.jpeg
 
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beerthief said:
never thought of trying to buy a low power 54 , i have a broken spring 54 i would like to rebuild at10 FPE , so if they make a 7.5 it must work .
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I don’t think turning a magnum springer into a sub powered rifle is the answer. Maybe bring it down from the 24 fpe the about 18 or 20 . Here in Canada they sell most airguns in a sub 500 fps version. Because they dont need a firearm license to purchase. I’ve had more than my fair share of them and can tell you they all shoot a lot smoother when tuned close to the advertised rather than low power. Mind you the manufacturers go through all sorts of methods to reduce power. This is the first that I’ve seen use a restrictive washer. The worst I’ve seen was a tiny bleed hole drilled through the face of the piston in combination with the full power gas ram. That was a crosman rifle , what a turd that was before the ram replacement.

This rifle in particular will have all ARH parts plus custom guides . Tuned to shoot at 20 fpe or close to that.
 
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beerthief said:
never thought of trying to buy a low power 54 , i have a broken spring 54 i would like to rebuild at10 FPE , so if they make a 7.5 it must work .
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Hector would be your best friend here but you knew that already. I don’t think I’d ever turn mine down though. I have enough target rifles and guns in 11-12 FPE range. I’ll just let the big dog eat!

@Hobbyman2007 my 56 runs a little over 18 FPE with the JSB 10.3. Spring in it appears to be OEM and looked in good shape so I didn’t replace. Interested to see what yours does with fresh ARH spring. Assume you’ve seen instructions on how to set tension after breech seal is replaced. Don’t want to melt a brand new seal. One of the advantages to Hecto’s tuner discussed above is the ability to tune to pellets. If your gun shows a liking for pellets other than the JSB, you can change that with the tuner. And if it likes them you can make it even better. It’s an amazing piece of kit.
 
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