Recently I replaced the springs and seals on a 25 and 27 model. (both .177)
Energy levels are now as follows:

both guns seem to perform best with H&N FTT 8.64 grain 4.52mm

25 (not D): 515 f/s or 5.09 fpe (maccari R7 spring)
27 : 565 f/s or 6.12 fpe (Chambers 300374 spring)

The energy seems to be stable now and not going up any more.

I am not really happy with these power levels.
I can live with the 25 being a 5 fpe gun, but the 27 (with more sweep-area and a larger spring should do better.

Compared with my 24 .22: RWS Hobbies average 523 f/s or 7.22 fpe
(so: the 24 shoots a .22 at roughly the same speed as the 25 shoots a .177)

I am thinking of selling these two "underachievers" and buying a new Diana 46C .177 instead (or a 300R). (and maybe another 24 in .177)

A question: does the 25D model perform better ? According to Chambers it has a different spring but is also tuned with R7 springs it seems. If one compares a 300294 with a Maccari R7, they seem like duplicates. But the R7 spring is better finished. This also goes for the 300374 and the Global Tarantula small XL: same dimensions, but the Maccari is better finished.
According to Chambers, the same spring (300294) is used for a 25 as for a 24, but I suppose the larger sweep-area of the 24 delivers more energy.

Please give me some wise advise. It's Chrismas time, remember...

I already replaced springs in Weihrauchs (97 .177 and 77 .25) and I always got the expected results. But the 2 Dianas really don't seem to perform.

Anyhow I wish you all a very nice and sweet Christmas holiday !

Joris

I am no expert mechanic, but you may want to recheck the spring spacing and seal fit on your guns?

My RWS-marked model 27, made in 1981, has recorded the following performances in the last few years. These are averages of 15-shot strings. The gun has its original spring and seals and has never been tuned or even taken apart, I just squirt a bit of silicon oil in it from time to time.

RWS Hobby, 692 fps, 7.5 fpe

RWS Superdome, 621 fps, 7.2 fpe

RWS Meisterkugeln, 618 fps, 7.1 fpe

Mauser Wettkampfkugeln, 668 fps, 7.4 fpe

Mauser Match, 645 fps, 7.5 fpe

Crosman Copperhead, 646 fps, 7.4 fpe

Daisy Pointed, 649 fps, 7.2 fpe

Ruko Match, 654 fps, 7.2 fpe

As far as I know, the models 25 and 25 D used the same factory spring.

Thanks for the reply.

I replaced the leather seal with a new one, so I suppose it must fit. But see my message of last week or so about the dieseling in my 27. Could it be that because of heavy dieseling (900 f/s with R10 heavy... I know I shouldn' say this) the seal got a looser fit ? It doesn't look broken though.
What also struck me is that the spring fits very tight around the spring guide.

Could this be the cause ??

Thanks

Joris

The spring guide should fit quite tightly when the spring is extended--this is what controls vibration and "twang" when the gun is fired. The fit will be looser when the gun is cocked, as the spring increases in diameter as it is compressed.

Leather seals are very strong and resilient. It is unlikely that a few diesel shots would permanently damage it.

Again, I am hardly an expert, but what kind of spring are you using? It may not be very well matched to the gun. Jim Maccari's springs are typically designed so that the coils are very nearly touching each other when the gun is cocked. Often some spacers have to be added to the ends of the spring to accomplish that. If not correctly spaced, even the best spring may return very poor velocities.

Thanks for the reply.

I installed this spring:

http://www.chambersgunmakers.co.uk/Diana-Original%20plans/Diana%2027%20plan.htm

It should be the correct one, I suppose.
For lubing, I sparingly used Maccari moly on the piston and heavy tar on the spring.

CU


Joris

Joris,

As, I don't care much about power from an air rifle, my addresses the consistency of performance of your Dianas.

How many pellets have you fired since you performed the mainspring changeover?

Are the D25 and D27 shooting where you aim at, say, 10m or 35m, depending on sighting-in method preferred?

In my case, after changing the spring in my D25 with the Beeman 7/Maccari-supplied -- recently -- it took up to 2000-3000 .177 cal. pellets to settle down to what I expected. Now, my D25 is performing better than ever before. It has all the accuracy I need (one hole @ 10m and an inch [1"] @ 30m. It also penetrates various objects, that the Chambers-supplied or the RWS mainsprins never managed previously. The Maccari (R7) spring & Black Tar, metamorphosed my D25, but it did not turn it into a mean hunting machine, by any means.

I like the Diana 25 and 27 models.

David Enoch

Hello David,

Could be difficult as I live in Belgium.
They are beautiful though, with minimal wear. 25 is from 1970, 27 is from 1971.

I have a 24 .22 "gallery model" (new) wich comes with sturdy fixed sights and no safety. I checked with the dealer and the same model is also availabble in .177.
In that case I would have a matching pair.
The good thing is that the fixed sights tend to shoot right on and center at 10 meter.

how can one post a picture here ?

CU

Joris