The trouble with Diana

[Wilfy]

Hi,
I bought a 1981 Diana model 24 .22 break barrel springer from the Birmingham international arms fair. Although the rifle appeared to be in good condition and worth the £75 that I paid for it, it has given me problems. Specifically as bought it was way down on power, to the point where I could not zero a scope on it because the shots were so weak and inconsistent. I considered returning it at the next fair but in the end I decided to strip the rifle down and investigate the problem. The components of the rifle seemed to be in good condition, the only thing I could criticise is that someone had used a screwdriver to remove the piston seal and caused a small amount of burring on the piston end.
The seal was old but I think it was still providing a reasonable seal, the spring actually measured up 1/4 longer than the length it should be. The spring did seem to be rather weak though, so I decided to fit a new spring and seals. The very helpful T. W. Chambers supplied a Titan Number 5 spring and the new seals. I was aware that I might have to cut the Titan spring down in length, it was actually 3 inches longer than the original spring. Subjectively comparing the new spring with the old said the titan spring was much stiffer and hard to compress than the old one. The preload with the original spring was 53 mm so even though this is my very first rifle rebuild 128 mm of preload seemed way to much. In the end I cut the spring 1 1/4 inches longer than the original. The intention with this was to have the spring an inch longer when I had dressed the end.
I cut the spring with a cut off disc in a dremel rotary tool, at first at an angle as best I could. once I had removed the bulk of the excess I could get in to cut the spring neatly at 90 degress to the coil. To provide the flat end I heated the end coil up with a pencil torch (mini butane blowlamp) and nipped the end down with some thin pliers. This took 3 goes to get the end properly profiled. I then dressed the end on a bench grinder and finally got a fine flat finish by rubbing the end of the spring on a sheet of fine abrasive paper on a sheet of glass. Fine carborundum sticks were used to smooth any sharp edges on the spring ends and also to remove any sharpness on the inside of the cylinder particularly the cocking lever slot so that the new seal could not be damaged by assembling it over sharp edges.
Assembling the rifle against the power of the new spring was hard work, I could compress it enough with both hands just about but I had to get her indoors to fit the retaining pins.
The result of all this effort, 4.76 FT/lb of power using 16 grain Air arms field pellets or 6.29 with the heavy (21.14 grain) Bisley Magnums. A decent rifle will go through the 3/8” plywood backstop that I use, this only dents the wood enough to lodge the pellet in place. This is disappointing, I had read so many forum reports of having to cut coils off the titan spring to stay legal i.e. below 12Ft/lbs. I would have liked to have seen 8 to 10 Ft/lbs at least. 11 would have been ideal. I really don't know where to go from here, for the moment I will live with it as it is, I believe I will be able to zero the scope and it will be usable up to 25 yards probably. I need to spend some time with it at the range to asses it properly.
I could look at fitting some spacers between the end of the spring guide and the spring to increase preload, Try another Titan spring cut to a longer length, more expense but as the spring fits a BSA meteor which I have 2 it may come in usefull.
Some general observations, the rifle now needs more effort to cock as expected, before you did not think about recocking it, now you have to concentrate a bit to do it. The Ft/lbs figures were arrived at using a Prochrono chronograph to measure the speed of pellet travel. I am well pleased with this, the only surprise was that different weight pellets did not vary in speed much. I used too much grease in the rebuild, Gunsmoke at the not OK corral. Any thoughts please.

[TonyL]

Hi Wilfy,

And a very warm welcome to this fine forum.

I don't think that there's a deal wrong with your rifle...

Firstly, the little 24 is a junior rifle, and a fine one at that, exhibiting lovely build and fine engineering and accuracy.

It will have limited swept volume and was never designed to make power approaching our legal limit. I don't know for sure, but I'd say that 6 to 6.5 foot pounds is about where it should be. I have one, a 24D. Can't remember exactly, but I think mine's doing just below 6, which I'm happy with as I have lots of other full power rifles. It shoots very sweetly and is accurate.

A couple of things :-

Even though you have shortened the spring, it's still probably "too much spring" for the gun. This is why cocking effort seems high. Recoil is possibly very high, too. And, sometimes, too powerful a spring can REDUCE power output, as the piston rebounds violently against the high pressure cushion of air, robbing the piston of forward momentum.

Also, even with higher powered springers, you will not normally gain high muzzle energy values with heavier pellets. As a very general rule, springers give more power with lighter pellets, and pneumatics with heavier pellets.

You could persevere with the Titan spring but, when you shorten a spring it actually becomes STIFFER. Personally, I would try and source a standard spring. If you can't obtain one in the UK, they can be had from Germany via mail order.....One of the members more versed in sourcing from Germany will be able to provide a link to a suitable site.

Get that little 24 running nice and sweet as it should be and enjoy it for what it is. If you need more power, there are many guns available which will be better suited to making higher power.

And well done on your work, it sounds like you performed a competent tune, there.

Hope you enjoy it on here - a fantastic place, full of nice peeps!

Please don't be afraid to shout up for any further help.

[TonyL]

Wilfy,

Pop onto the Useful Airgun Section. Scroll down a little and you'll come across the Mainspring Data Thread. Post #7 by Phil Russell gives dimensions of the Diana 24 spring.

Had a quick look on google, typing in "Diana 24 mainspring". Not far down the list is Progunner from Sweden, who are listing a genuine spring. There will be others, I'm sure, if you search.

Many members here have played with these and use them as shorter range target rifles and may well be able to give their recommendations.

Keep us posted.

[oliver13]

It's always worth giving the barrel a good clean & thorough inspection, especially as it's secondhand gun - you don't know whats been through it, but I don't think it's a full power gun anyway, as said, I think it's more of a garden plinker for youths.

For what it's worth I tried a bigger spring in my Airsporter years back & it was less powerful, it was pre chrono days but they were going into wood a lot less than the ones with the original spring, & when I took it out after a week it had been chewing up the inside of the piston & the gun was full of swarf.
Titan springs I've used always need cut down & seem stiffer than the originals, I'd cut it to the same length as the original one & take it from there, but they're not cheap either, you can always cut them shorter but if you go too far you can't put it back...

[DSidelever]

Tony has covered it really!

M&G (Diana) made a range of Youth Guns, your model was especially popular in the States, in .22, some people felt the larger calibre was the smoother shooter.

They can be very accurate and they mostly very well made.


Welcome from another newbie ! (oldbie really)

[DSidelever]

Because the gun sold so well in the States there is stack of info available on the Dianawerk Collective Forum (you dont have to be a member to undertake a Search of the forum and entering "Diana 24" throws up page after page of threads). Unfortunately the site navigation on there is a bit poor at times only allowing 1Thread per search - just keep going back to the Search box.

I find RWS Superdomes do well in my Diana springers and as Tony said, lighter is usually better.

Here's a quote for you !!!
'Hey,

I'm a Sgt in the 103RCACS North Vancouver and I have just one word of advice for you. Regardless of what you have heared, the mod.24 is a good airgun. I have tried numerous airguns in my cadet career such as the Daisy 853 which I shoot in competisons (however you spell that word) and let me tell you, I am always happy to come home to My 700 FPS diana mod.24 (and yes it really dose go that fast). But as for upgrading it I do agree that you monies are best spent just buying a bigger Diana airgun.'

ATB

[Wilfy]

Thanks for the info everyone. I think I will leave the rifle as it is for the time being. Even with the inch longer spring it does seem to shoot well, there is no sign of harshness when firing and recoil is minimal. I need to spend some time with it at the range. I believe I will be able to zero the scope now which will solve the original problem. I definately think trying it out properly first is the right thing to do. If it is practical at 20 or 25 yards then that will be ok for me.
T.W.Chambers list what I believe is an original spring as well as the Titan XS one. In practise If it proves necessary then I could cut the Titan one down to the length of the original as this would save the cost of another spring. When I have had chance to try the rifle out properly I will report here as to the results.

[Phil Russell]

I cannot add to what TonyL has said ...
A 24D I reworked a while ago shoots at 550 - 600 fps in .177, depending on pellet, and I thought the (original) spring to be a little tired. I came across some reference to an output of c. 700 fps but pellet was not specified. I have a Webley AirWolf in .22 .... apparently identical to the Diana 24 (not quite same as 24D which has a different trigger) and that produces c. 7 ftlbs so I suspect c. 6 ftlbs in .177 is about right.
If you are brave you could well try nipping another half coil off the spring ... it may seem counter intuitive but I have shown several times that too much spring is a bad thing.
Good luck ... superb little rifles.
Cheers, Phil

PS: I am still looking for an AirWolf safety catch .....