by Tom Gaylord
Writing as B.B. Pelletier

Diana Stormrider II
Diana Stormrider Generation II precharged pneumatic air rifle.

Part 1
Stormrider Gen 1 Part 4

This report covers:

  • Fill
  • RWS Superdome
  • Discharge sound
  • JSB Exact Heavy
  • Chronograph
  • Last pellet
  • Discussion
  • Trigger pull and adjustment
  • Summary

Today we look at the velocity of the .177-caliber Diana Stormrider. I linked to Part 4 of my test of the .22 caliber rifle last year for comparison, but the rifle I’m testing today is a .177-caliber second-generation airgun, where that last test was a first generation. Part 1 of this report discusses the differences.

In Part 1 of this report I made a big deal about this Stormrider’s fill adaptor coming with a male Foster fitting on the end that connects to the hose of most air tanks. However, in re-reading the other report I see that the Gen 1 gun had one, as well, so Diana has thought this through from the very beginning.

Fill

I started by filling the rifle to 3000 psi (206 bar). That’s over the recommended fill pressure of 200 bar/2900 psi, but the fill went too fast to stop it in the correct place. The reservoir is small, so it fills fast.

RWS Superdome

The first pellet I tested was the RWS Superdome. This 8.3-grain dome averaged 1,043 f.p.s. out the muzzle for 10 shots. The low was 1035 and the high was 1053 f.p.s. for a spread of 18 f.p.s.  At the average velocity this pellet generates 20.05 foot pounds at the muzzle, so we are already at the listed energy. We are also above the listed velocity of 1,050 f.p.s., and we did it with a middle-weight lead pellet.

Discharge sound

The discharge sound is low for this power level. It’s too noisy for a small suburban back yard, but it is not offensive. A reader asked if the Diana silencer is equivalent to a TKO silencer and I have to say that it isn’t. A TKO does more to attenuate the discharge. But this one is doing a good job.

JSB Exact Heavy

I tried the JSB Exact Heavy dome dome next. The rifle seemed to fall off its power curve around shot 2 in this string which is shot 12 from the initial fill, so I will show you the entire string.

Shot…………Velocity
1………………991
2………………983
3………………976
4………………966
5………………966
6………………953
7………………950
8………………936
9………………931
10……………..923

Therefore, the following data is pretty useless. The average for this string was 958 f.p.s. The spread went from 923 to 991, a range of 68 f.p.s. At the average velocity this pellet generated 21.08 foot pounds at the muzzle.

To see whether I was right about the power curve I shot another RWS Superdome that went out at 970 f.p.s. That’s far below the average 1,043 f.p.s. I got on the first string.

There is something else that’s interesting within this string. Do you see how the velocity sort of stabilizes around 950/960 f.p.s. (shots 4 through 7)? That tells me the real drop-off point was there, rather than at shot 2 like I mentioned. Just looking at this data I will guess that if I were to run a second string after filling the rifle to 2900 psi again, the average with this pellet would be around 970-980 f.p.s. I’m guessing that if I were to re-run the test after filling, this pellet would probably generate around 22 foot pounds. Let’s test it and see. For this test I re-filled the gun to 200 bar/2900 psi.

Shot…………Velocity
1………………961
2………………972
3………………980
4………………988
5………………993
6………………989
7………………989
8………………990
9………………990
10……………..979

The average for this string was 983 f.p.s. The spread went from 961 to 993 f.p.s., a range of 32 f.p.s. At the average velocity this pellet generated 22.19 foot pounds at the muzzle. It looks like I made my velocity estimate after seeing these numbers but I didn’t. I guessed, based on the velocity I saw in the first string with this pellet. This also affirms my thoughts that the end of the power curve in that first string was around 950 f.p.s., and that gives us a shot count of 17 shots per fill.

Chronograph

I’m only setting these limits (shot count and power curve) based on the numbers we are seeing from the chronograph. You can choose different numbers and extend the shot count if you like. I am always thinking forward to the accuracy at 50 yards, where small velocity variations are more important, but if you are happy shooting at 25 yards, then don’t stop where I did. All of this is arbitrary and gets selected by the results you see. This is a good illustration of why you need a chronograph and to not just listen to the speed of the shot from your back door to the hickory tree.

If you don’t have a chronograph, just shoot groups at 25 yards or beyond and stop shooting when the pellets start to drop. That’s a practical way to operate.

Last pellet

This Stormrider is a powerful air rifle, so I’m not going to shoot ultra-lightweight pellets in it. I don’t want to break the sound barrier. The last pellet I will test is the Crosman Premier Heavy dome. This test turned out to be the most interesting of all, so look at the results and then we’ll talk. For this test I filled the rifle to 206 bar/3000 psi.

Shot…………Velocity
1………………882
2………………922
3………………919
4………………919
5………………926
6………………930
7………………950
8………………955
9………………962
10……………..966
11……………..974
12……………..977
13……………..978
14……………..972
15……………..971
16……………..970
17……………..965
18……………..959
19……………..949
20……………..943
21……………..937
22……………..931
23……………..922
24……………..913

The first comment I will make is that the gun was filled too high at the start of this string. The velocity increase over the first 6 shots tells you that. If we start our power curve at shot 6 and continue to shot 22, there are 17 good shots on this fill. Imagine that! But there is something additional to look at here.

Do you see how slowly the rifle falls off the power curve at the end? It seems to be fighting to keep shooting. If you don’t want to shoot 50 yards you can start the curve at shot number 2 and stop at shot 23, giving you 22 good shots on a fill. Or stop at 18 because that is two full 9-shot magazines.

I think the heavier Crosman pellet remains in the barrel longer, holding the valve open just slightly longer and giving this improved performance. If we go with the part of the curve I selected (shots 6 through 22) the average velocity is 958.12 f.p.s. The spread for that string runs from 930 to 978, which is 48 f.p.s. At the average velocity the muzzle energy is 21.41 foot pounds.

Discussion

Diana has given very conservative numbers for their .177-caliber Gen II Stormrider’s performance. They say 1,050 f.p.s. and we see more than that with a middleweight pellet. They say 20 foot pounds and we have seen over 22 foot pounds.

Also, this Stormrider likes heavier pellets the best. They seem to work well with the way the valve is set up.

Trigger pull and adjustment

The Gen II trigger is adjustable. Unfortunately Diana didn’t put the directions for adjusting it in the manual. I discovered that both the front and rear screws affect where stage one stops and stage two begins, and no amount of adjustment gets rid of all the creep in stage two. It came from the factory with a long stage one that was a pound and a short creepy stage two that breaks at 4 lbs. 15 oz. After a lot of fiddling I got the long stage one at a pound and a fairly crisp stage two at 5 lbs. 5 oz. I like a positive release over a light trigger so I’m leaving it where it is.

I don’t have any specific instructions for you. It seems like the front trigger is for the stage one length of pull and the rear screw is for the let-off weight. But both screws seem to affect both adjustments, so who really knows?

Summary

The Gen II Stormrider is shaping up nicely. It has good power, is reasonably quiet and gets a full two magazines per fill. If the accuracy is there this will be a best buy.