by B.B. Pelletier

The term ACCURIZED is so common in airgunning that people use it without thinking. What does it mean?

As far as I can tell, Robert Law of Air Rifle Headquarters (ARH) was the first to use the term ACCURIZE in relation to airguns. You would think that he had a specific definition in mind, but when you read what he wrote in his Fall/Winter 1979 catalog to describe the term, you’ll see it doesn’t seem to amount to much.


A late ARH catalog gave the definition of accurization.

“Accurization involves having a highly trained specialist totally disassemble a gun. Each individual part is cleaned and inspected. The ultimate space-age lubricant or bonded coating is then applied to each component for optimum performance and friction reduction. This stabilizes the cylinder compression mechanism and greatly reduces normal wear. Both accuracy and velocity improve. Recoil is often reduced by as much as 60 percent.”

That is the only paragraph out of four under the heading Optional Accurization that has any technical information in it, and, as you can see, what is there is pretty thin. It sounded good to me when I read it for the first time in 1979, but now that I’ve tuned a few guns, it doesn’t hold much water. However, let’s not stop there.

I have encountered the results of an ARH “Optional Accurization” and can report to you what I found. A friend acquired an FWB 124 that wasn’t performing well and asked me to overhaul it for him. It had been accurized by ARH and not touched since. When I removed the action from the stock, I was shocked by the large amount of what looked like moly grease that had escaped the cocking slot and was now coating the outer surface of the spring tube. I scraped about a teaspoon of this gray viscous grease from the outside of the spring tube around the cocking slot, which told me to expect many times more inside the tube.

There was more, but not as much as I feared. The grease had been slowly migrating outside through the cocking slot, so I found a couple more teaspoonfuls inside, but no more. I was curious why this rifle was so loaded with grease, and the answer surfaced in an ARH pamphlet about accurizing FWB 124s. The instructions advised the use of Moly G powder everywhere on the inside of the 124 action except on parts relating to the trigger. They go on to say that an entire jar of Mainspring Dampening Compound should be spread on the mainspring. The ARH jar of Mainspring Dampening Compound held 1/2 oz. of thick white silicone grease. That’s about four teaspoons full.


This pamphlet, published in 1976, describes what goes into an accurization.

Inside the gun, the lubrication (grease) had moved to the cylinder walls, so the mainspring was free to move. However, if it tried to wiggle against the cylinder walls it came in contact with this thick grease that dampened its vibrations. Over the course of the years, all the dark Moly G powder had mixed with the Mainspring Dampening Compound until what remained looked like a thick gray grease.

Before my tuneup, this rifle was shooting Crosman Premier 7.9-grain pellets around 730-750 f.p.s. After I tuned it up and switched out the mainspring and seal, it shot 960 with the same pellet.

The velocity reported in the preceeding paragraph is in error. The final velocity wasn’t 960 f.p.s., it was 861 f.p.s. A reader of this blog named Lance pointed this out to me and I found the report in the November 1997 issue of The Airgun Letter. I apologize for this mistake.

Mainspring Dampening Compound was good stuff back in the 1970s, when factory mainsprings were loose both inside the pistons and on the spring guides. By the mid-1990s, tuners such as Ivan Hancock and Jim Maccari were telling everyone that the physical tolerances inside spring guns had to be made tighter and the lubrication had to be minimal. Hancock coated certain of his springs with a permanent black substance that I referred to in The Airgun Letter as Black Tar, a term that caught on. Maccari soon came out with a different black tarry grease that home tuners could apply, and, because it didn’t rob velocity when done correctly (like the old Mainspring Dampening Compound had) he dubbed it Velocity Tar.

By the 1990s, most airguns in the higher-powered class were also using synthetic seals instead of leather. Let me tell you what that means. A tuned RWS Diana 45 with a leather seal can make about 840 f.p.s. with a light .177 pellet. With the same pellet in the same rifle converted to a synthetic seal, the velocity rises to the high to mid-900s. Before you start thinking about replacing leather seals with synthetic, however, know that most airguns will require a new piston for the synthetic seal – it’s not a straight swap. Those guns that do have the leather seals are starting to have some collector value. I once converted an HW55 from a leather seal to synthetic and now I wish I hadn’t, because with leather the gun is a better collectible.

At Beeman, the term was a “Super Tune-Up.” I won’t say that what they did was essentially the same as the ARH accurization, because I don’t believe they ever used Mainspring Dampening Compound (which they also sold) to the same extent. Also, they were in business later, so they had some tunes like the Laser Tune that were far more modern than those done by ARH. A laserization involved a fitted piston seal, a mainspring that was easier to cock and a new gold lubricant called Laser Lube. Together, these things boosted the R1’s velocity up to 1,100 f.p.s.

At ARH the term accurization was used loosely, and the procedures to do one probably evolved as time passed. Nobody would want a 1970s tune on their gun today. A 1976 FWB 124 got about 820 f.p.s. when tuned to the max, and the 124 has always had a synthetic seal. It also vibrated a little after tuning. With a good tune today, it’s possible for the same rifle to reach 960 f.p.s. with the same pellet and be almost dead calm.

The bottom line to this report is that accurization is a nebulous term with no foundation in fact. It is about as descriptive as the term “Magnum,” which used to mean an airgun that could shoot faster than 800 f.p.s., but today means faster that 1,000 f.p.s. In 10 years, who knows what it will mean?