Diana Model 20 Youth Part 2

The Diana Model 20 was produced from about 1922 until 1940.


Shooting the Diana 20 is a pleasant experience.  Being a kid-sized gun, the cocking effort is kid-sized, too: only 10 pounds.  The barrel breaks easily and the spring compresses very smoothly with no crunching sounds.  As with most airguns of this era there is no safety or anti-beartrap mechanism.  It is possible to decock the gun by breaking the barrel completely down and, while holding the barrel, pull the trigger and let the mainspring decompress.

I did disassemble this gun to clean and properly lube the internals; there was no special work done that could be considered a "tune".  However the shooting cycle is still very smooth and the noise level is low with no spring buzz.  Since the Model 20 is so light it does move a bit when fired.

Velocities
Testing was done with a fairly wide range of pellets weighing from 4.2 to 8.6 grains.  Velocities ran from the upper 300's to the upper 500's.  The extreme spread with several pellets was 5 feet per second or less; I have seen this from a number of lower powered spring guns that have fired many thousands of pellets.  My assumption is that all of the parts are well broken-in and with modern pellets the results are very consistent.  Muzzle energy ran from 2.4 to 3.2 Ft Lbs depending on the pellet; not enough for ethical hunting but just perfect for short range plinking.


PelletGrainsFPSFt LbsESNotes
Coal Field8.43842.88
Crosman Destroyer7.73962.74Vertical stringing
Falcon Accuracy Plus7.34303.05
GTO WC5.24982.95Horizontal stringing
H&N Econ II7.44152.812Poor accuracy
H&N Excite Plinking7.14202.823
H&N FTT8.63852.820
JSB Exact8.43942.96
JSB Simply WC8.23742.58
RWS GECO7.04423.014Best accuracy
RWS Hobby7.04573.216
RWS Super HP7.04212.86
RWS Super Point8.23642.414
Webley VMX7.94022.83
Winchester MVP4.25763.118

PelletGramM/SJouleNotes
Coal Field0.541173.8
Crosman Destroyer0.501213.7Vertical stringing
Falcon Accuracy Plus0.471314.1
GTO WC0.341523.9Horizontal stringing
H&N Econ II0.481273.8Poor accuracy
H&N Excite Plinking0.461283.8
H&N FTT0.561173.8
JSB Exact0.541203.9
JSB Simply WC0.531143.4
RWS GECO0.451354.1Best accuracy
RWS Hobby0.451394.3
RWS Super HP0.451283.8
RWS Super Point0.531113.3
Webley VMX0.511233.8
Winchester MVP0.271764.2


The single-stage trigger breaks at around 5 pounds.

Accuracy
Getting the best groups with the Model 20 takes concentration: the light weight and heavy trigger work against you.  The single stage trigger breaks at about five pounds and has some creep that is really noticeable when target shooting.  For informal shooting it is less of an issue.

Diana described the Model 20 as having "good accuracy from 6 to 8 meters" in its advertising from the 1920's but with the right pellet the 20 can give surprisingly small groups.  Most other pellets gave groups around three-quarters to one inch at 8 meters and a couple were just awful.  Getting the best accuracy does take a good deal of effort due to the gun's light weight, heavy trigger, and basic sights.

All targets below are five shots each at 8 meters.

RWS Super Hollowpoint pellets: .66" / 16.7mm.


H&N Field Target Trophy pellets: .57" / 14.5mm.


RWS Super Point pellets: .41" / 10.4mm.


Webley VMX pellets: .80" / 20.3mm.


H&N Excite Plinking pellets: .59" / 14.0mm.


RWS "Geco" pellets: .42" / 10.7mm on the left and .27" / 6.9mm on the right.


Any of the pellets above are completely adequate for short range plinking, and I was pleasantly surprised how well the Geco pellet did considering its low cost (relatively speaking.)  With a little holdover it was pretty easy to hit 3-inch diameter pet food cans at 25 yards!


Construction details
The Model 20 has a leather piston seal so it will need occasional oiling but should last many years.  I used an o-ring to replace the flattened leather breech seal.  If you disassemble the 20 there is one trick getting it back together.  Due to the construction of the compression tube an inner sleeve is used to provide a solid wall to seal the cylinder; this creates a ridge, or step in the inner diameter of the cylinder.  When the piston is removed the seal will expand slightly and hang on this step when the piston is replaced.  What I had to do was to wrap a couple of layers of painter's tape around the piston seal and then compress it with a hose clamp.  After sitting a couple of hours the seal's size was slightly reduced and the piston dropped into place easily.  After two of three shots the seal was back to its proper size and the gun performed normally.



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