by Tom Gaylord
Writing as B.B. Pelletier

Diana 5V pistol
Diana model 5V pellet pistol.

Part 1

A history of airguns

This report covers:

  • RWS Hobbys
  • JSB Exact RS
  • What is dieseling?
  • Sig Match Ballistic Alloy
  • Cocking effort
  • Trigger pull
  • Next
  • Observations

Today we look at the power of my old Diana model 5V air pistol. I expected to see results in the same class as the BSF S20 and Webley Hurricane, but perhaps a little slower because of the age of this airgun. I reckoned somewhere in the high 300s, at least.

RWS Hobbys

The first pellet I tested was the RWS Hobby, which is often the standard for velocity in an airgun. In the 5V Hobbys averaged 397 f.p.s., which I think is a pretty healthy result. The low was 387 and the high was 408 f.p.s., so the spread was 21 f.p.s. At the average velocity, this pellet produced 2.45 foot pounds of energy. I will add the Hobby fit the bore pretty tight.

JSB Exact RS

Next up were JSB Exact RS pellets. This domed pellet fit the bore better and went in deeper. They averaged 420 f.p.s., despite being 0.33 grains heavier. The spread was from 396 to 431 f.p.s., which is 35 f.p.s.. At the average velocity this pellet produced 2.87 foot pounds of energy.

I want to note that of the three pellets I tested, this was the only one that caused the pistol to diesel. There was no noice, but the barrel filled with smoke with every shot. Whether that is important will have to wait for the accuracy test, I guess.

What is dieseling?

Dieseling is normal in spring-piston airguns. Thgose that shoot over 400 f.p.s. all do it to some extent. Dieseling is the rapid combustion of tiny oil droplets from the heat of compression. According to the Cardew team of father and son who wrote the book, The Airgun From Trigger to Target, dieseling is a normal function of spring-piston airguns, once they reach a certain power level. It adds a certain percentage to the muzzle velocity.

Don’t confuse dieseling with detonation, which is a loud explosion of rapidly burning oil. Dieseling produces smoke without any flash or loud explosions.

Sig Match Ballistic Alloy

The last pellet I tried was the lightweight lead-free Sig Match Ballistic Alloy pellet. They turned the 5V pistol into a screamer, with an average velocity of 485 f.p.s. The spread went from a low of 469 to a high of 489 f.p.s., which is 20 f.p.s. At the average velocity this pellet generated 2.74 foot pounds of muzzle energy.

Oddly enough, even though this pellet was much faster than the JSB Exact RS pellets, there was no indication of dieseling. The pistol must be right on the cusp of what it takes to diesel and the RS pellet must be right for the job.

Cocking effort

The 5V cocks easily for me. I measured the effort at 23 lbs. Those other powerful spring-piston air pistols I mentioned earlier all cock with over 30 lbs., so this one feels light.

Trigger pull

The trigger, on the other hand, is extremely heavy. My gauge goes up to 12 lbs. and this trigger is much heavier than that. I estimate 18 lbs. It’s like the trigger on the Swivel Machine Corp Stealth arrow launcher, which has the heaviest trigger I have ever tested.

However, as I was shooting the strings, several shots were lighter by about half. That gave me some hope that this trigger will respond to some moly grease in the right places.


Normally I would test accuracy next, but given how heavy this trigger is, I think I will take the action out of the stock instead, and see if I can do anything with the trigger. I don’t want to disassemble the action, so I’m hoping to find a way to grease the trigger and sear once the gun is out of the stock.


I wasn’t expecting this pistol to be as powerful as it is — especially not after reading Fred’s review of his .22. I guess this one is fresher than it appears. I hope it is accurate.