by Tom Gaylord
Writing as B.B. Pelletier

Part 1

diabolo pellet
The diabolo pellet exists in four smallbore calibers.

This report covers:

  • History
  • Back to Sheridan
  • Early success — sort of
  • Why .20 caliber?
  • The next speedbump
  • Boom
  • Bust
  • Summary

Today we take a look at the .20 caliber that is also popularly labeled as 5 mm. There were Quackenbush airguns in the late 19th century that were made in .21 caliber and Crosman made some gallery airguns in .205 caliber, but the true .20 caliber didn’t exist until it was created by Sheridan in 1947.


According to Ronald Elbe’s book, Know Your Sheridan Rifles and Pistols, 2nd edition, copyright 2018 by Ronald E. Elbe, the 5mm pellet (and airgun) existed in Europe prior to the launch of the Sheridan model A (the Supergrade) in 1947. This is the first time I have been aware of that fact. To the best of my knowledge, only the Zimmerstutzen parlor rifle existed as a 5mm, and that size was at the high caliber range of the rifle. It would be a new ball size 21 or an old ball size 17. But a zimmerstutzen is a firearm by the strictest definition, so I need to find out more about the existence of these pre-Sheridan 5 mm airguns.

Back to Sheridan

At any rate, Sheridan’s model A was fielded in .20 caliber in 1947 and the company maintained that caliber for all their airguns until the company was sold to Crosman. The late Ted Osborn told me that the prototype model A rifle was made in .22 caliber for testing purposes, since .20 caliber pellets were not available.

Sheridan called their new pellet a cylindro-conical design. And they stayed with that shape for the entire time the company was owned by them. In 1977 they did buy a European diabolo pellet and sell it under their brand name, but the mainstay pellet was the good old Sheridan cylindrical.

Sheridan Cylindrical
The Sheridan Cylindrical pellet has no wasp waist, but it does have a hollow tail to move the center of mass forward. The step at the base of the pellet takes the rifling.

Early success — sort of

The model A/Supergrade was a success from the standpoint of accuracy and power. Even the fine British and European pellet rifles of the day were only its equal for power and accuracy. They also equaled the Supergrade for build quality, but they didn’t surpass it. I’m using the Webley Mark III and the Diana model 58 as my comparisons.

The Supergrade has a walnut stock and separate forearm and a large cast aluminum receiver. The rifle itself is no bigger than a Sheridan Blue Streak, but when you take the time to really examine it, the quality is revealed. The valving mechanism is another place quality reigned, but that’s not visible outside the airgun.

All that quality cost money, though, and a retail price of $56.50 in 1947 was too much to pay for an air rifle. The model B that followed at $35 didn’t help sales much. Not until 1949 and the model C that was also called the Blue Streak and Silver Streak, retailing for $23.95, was Sheridan’s place in the market assured. Even then, though, both the Crosman and Benjamin pneumatics were cheaper.

Why .20 caliber?

The question everyone asks is why did “they” (Ed Wackerhagen and Bob Kraus) produce their first airgun (and all subsequent Sheridan airguns) in .20 caliber, when there was no good source of supply for the pellets? Some believe they wanted to corner the market, but that would be like a mouse wanting to subdue an elephant! It just isn’t a viable possibility. I choose to believe the inventors, who said they did it because, and I am putting their stated remarks into a succinct statement, “We simply wanted our gun to be the best. By controlling the ammunition as well as the manufacture of the rifle, we could ensure this.” What they were saying is neither .177- nor .22-caliber airgun pellets of the time were of high enough quality for the gun they wanted to make.

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The next speedbump

So, Sheridan was the standalone user and supplier of .20-caliber/5 mm airgun pellets from the late 1940s until…? Well — until Dr. Robert Beeman decided to brand .20 caliber/5 mm airguns and pellets, sometime in 1981. Their 1980 catalogs (numbers 7 and 8) both say that .20-caliber/5 mm pellets are restricted to the Sheridan brand rifle, while in their 1981 catalog (number 9) they say they have developed the first precision-waisted (diabolo) pellets and followed that with the first spring-piston air rifle in that caliber — a Beeman 250, which is based on a Diana 45. Of course to get things like this into the catalog they had to be working on these things a couple years before.

In their 1982 catalog (number 10) they proudly display the new 5 mm (.20 cal.) Beeman R5 rifle on two pages. The R5 was available only in that caliber, so that marks the first big push Beeman made for this caliber.  In 1982 they offered the following pellets in .20 cal.:

  • Silver Bear
  • Silver Jet
  • Bear
  • Sheridan

Beeman R5
The Beeman R5 was produced in 5 mm only. It didn’t last long.


Following that Beeman’s push for the .20 caliber took off. But the promotional literature — mainly the catalog — maintained a stable encouragement for all three calibers — .177, .20 and .22 The .25 caliber did exist at the time but it was at a low point around the world — especially in the US, Europe and the UK. That would soon change, but in 1990/91 Beeman started a full-court press for the 5 mm/.20 caliber. Many of their German airguns were offered in that caliber, though none of the UK guns just yet. The FWB 124 and 127 (.177 and .22 caliber, respectively) almost got a companion in the 5 mm 125. But that model was stillborn for reasons to which I am not privy.

Robert Beeman said the .20 was a good compromise between .177 and .22. I always felt it was closer to .22 in terms of power for hunting. But you still couldn’t shoot anything except .177 in formal target competition. And in field target any caliber larger than .177 put the shooter at a statistical disadvantage.

The .20 caliber blossomed in the 1990s and carried over into the new millennium for several years. The Brits finally embraced it as a good compromise between .177 and .22. The Koreans and Turks included it in their PCPs, as did AirForce Airguns, who still offers it in several of their smallbore rifles and their exchange barrels.


Twenty years into the new century and millennium the era of the .20 caliber is fading rapidly. Pyramyd Air offers just 6 different pellets in this caliber and one of them is a felt cleaning pellet! There are other pellets out there that Pyramyd doesn’t sell, but nothing like what’s available in .177, .22 and even .25. If there aren’t many pellets there won’t be many new .20-caliber airguns. It’s easier for a PCP with interchangeable barrels like what AirForce makes to stay with the .20 than it is for an airgun to be entirely dedicated to the caliber.


Will the .20-caliber/5 mm go away completely? Probably not. At least not right away. But the demand for innovation in this caliber just isn’t there today. Of the four smallbore calibers it is number four.