Pellet calibers — why .25?: Part 4
by Tom Gaylord
Writing as B.B. Pelletier
The diabolo pellet exists in four smallbore calibers.
This report covers:
- When I got into airgunning
- Others abound
- Springers, too
- Is it possible?
This is the final installment of this series. Today we look at the big quarter-inch bore — the .25 caliber pellet. This is the largest of the four smallbore airgun calibers, and for years there was nothing larger. The .25 has occupied a niche of its own.
The .25 caliber diabolo pellet came into being a few years after the .177 and .22 — around 1908, or so. Yes, there were smoothbore airguns in the late 1800s in both .22 and .25, with the Gem being one of the most notable. Many dart guns were also made in .25 caliber. But it was George Lincoln Jeffries’ “H. The LINCOLN” air rifle of 1905 that started smallbore airguns in a big way. In a few years BSA, who produced the Jeffries rifles, had taken over, and the BSA rifle that reader RidgeRunner talks about all the time is a direct descendant.
H. The LINCOLN underlever spring-piston air rifle was loaded through a rotating tap on top of the receiver.
These early air rifles were spring-piston, which gave the advantage to the lighter .177 caliber. The .25 caliber was introduced as early as 1906, but took several years to catch on. In the early years .25-caliber wasn’t much of a competitor and never caught on in the United States, where .22 caliber soon rose to the top. The .25 went too slow and produced an arched trajectory that was apparently too difficult to deal with.
The Benjamin Air Rifle company and Crosman could both have taken advantage of their pneumatic powerplants that would have been better suited for the .25 caliber pellets than spring-pistons, but they never did.
When I got into airgunning
As an adult I got into airgunning around 1976 with the purchase of a Diana model 10 pistol. But it was the purchase of Volume 1 of Air Gun Digest, written by Robert Beeman, that started my interest in vintage airguns. Ironically, that happened not too long after I bought the pistol. I was serving in Erlangen, Germany, and in 1977 a copy of the book appeared one day in my Stars and Stripes bookstore on post. I nearly wore that book out (I still have it), reading about a world of airguns that I never knew existed.
In those heady days of the late 1970s the airgun velocity wars had just started. By 1980 I was back in the States and really delving into airguns seriously, but .25 caliber was nowhere to be seen. Dr. Beeman called the .25 caliber “near obsolete” in Airgun Digest and in 1976 when he wrote that, it was. However, it wasn’t quite dead — not yet.
In 1994 Diana started offering their model 48/52 sidelever rifle in .25 caliber. We airgunners all thought it would be a real powerhouse, but the truth was, it left us flat. The Diana 48 in .177 was a powerhouse, at over 1,100 f.p.s. and the .22 was powerful, as well, but the .25 left us wanting. Apparently there wasn’t enough swept volume in the sliding compression chamber to generate enough compressed air to send the big 6.35mm pellets out at more than around 635 f.p.s., give or take. The BSA Lightning XL breakbarrel did just as well and weighed several pounds less — a tribute to swept volume over the power of the mainspring.
What we didn’t perceive in the 1990s when all this was happening was that precharged pneumatic (PCP) airguns that were on the horizon were about to change everything. They were the “dark side” in 1995, but in 2021 they are mainstream. And pneumatics make all the difference in the world!
Today we have .25-caliber rifles shooting pellets capable of supersonic flight, which means they can also handle very heavy pellets. That is perhaps the biggest advantage they have over the .22 round. The AirForce Escape, for example, lists a velocity of 1,145 f.p.s. in .25 caliber. This is a rifle that’s so powerful that it isn’t even offered in .177, because why would you want one? Sure, you can fit a .177 barrel to an Escape but the valve won’t be optimized for it. The Escape is an all-out PCP for hunting. Plinking with it is like plinking with a .454 Casull Magnum. Sure it can be done, but that wasn’t the reason it was developed.
And the Escape isn’t the only game in town. Don’t overlook the Condor. And Hatsan has the AirMax, the Flash, the Hydra, the Hercules Bully and so on. Crosman has numerous incarnations of the Benjamin Marauder and the Kratos. And the beat just goes on and on.
There are also a few spring-piston rifles that at least claim to shoot .25-caliber pellets at or above 900 f.p.s. The springer has never been the powerplant of choice for the quarter-inch bore, but some of today’s spring rifles are capable of good power that, unfortunately comes at a price of hard cocking and violent shot cycles.
To get the power to push heavy .25-caliber pellets a spring-piston rifle needs a long stroke and a fairly wide piston. Unless the rifle is specifically built for that caliber as the Sig ASP20 is specifically built for .22 caliber, the shot cycle of an untuned rifle will be harsh.
Now I own a spring-piston rifle in .25 caliber that produces over 30 foot-pounds and is absolutely dead calm. So it can be done. But my Whiscombe is one of less than 500 rifles ever made by the late John Whiscombe and to buy one you’ll pay four figures.
Is it possible?
Could someone make a dedicated .25-caliber spring-piston air rifle that was smooth, and easy enough to cock? Of course. But it would take a concerted effort from a company willing to invest a large percentage of the time of several engineers over a period of perhaps 18 months. Are there enough potential sales of .25 caliber breakbarrels at the $400+ mark to justify an investment like that? Probably not. You see, it’s not just a matter of a more powerful mainspring. The Hatsan 135 QE Vortex cocks with 57 pounds of effort and still only delivers velocities of 750 f.p.s. in .25 caliber. Compared to the spring guns of yesteryear that’s magnum performance, but so many PCPs leave it behind that there is no comparison.
I count 19 different pellets for sale in .25 caliber. Only the .20 caliber offers less choice. The pellets that do exist come from premium manufacturers which means they should all be good, but it also means they won’t be cheap. Don’t envision shooting a .25 only to discover after buying the airgun that you don’t want to pay for the ammo!
The PCP is far better suited to .25 caliber. It has the power to make trajectory concerns a non-issue. Given that, the .25 caliber pellet is the number one smallbore pellet choice for small game hunting.
The market seems to be expanding cautiously for the .25 caliber airgun and pellet. PCPs now dominate .25 caliber with the greatest potential for advancement remaining in the spring-piston arena (because they have so far to go). Only the CO2 powerplant is not a big player as the rising tide lifts most boats.
The .25 caliber has finally arrived — about a century after its introduction. In the smallbore airgun world it is at the top of the heap. But you must understand that its performance comes at a cost.