by B.B. Pelletier

Last week, our new reader, Cantec, mentioned that several gentlemen were advising the use of corn oil for lubricating the compression chambers of spring-piston airguns. I know exactly where this recommendation came from and how it should be viewed, and I wanted to share this with you today.

Corn oil?
Yes, I’m talking about common corn-based cooking oil. Wesson oil is the most popular brand here in the U.S. Why would anyone recommend using corn oil in a spring-piston airgun? I want you to know the entire truth so you don’t make any serious mistakes with your guns.

Good old corn oil that’s most often used for cooking has also been used to lubricate some spring-piston airguns.

In my role as a firearms enthusiast, I used to put WD-40 on all my guns. It smells so good and guns always look so nice after they have been wiped down with it. So, when the Army sent me to Germany for four years, I sprayed WD-40 on all my guns before storing them in my mother’s attic, thinking I was protecting them against the ravages of time. What happened, instead, was that the WD-40 dried out and left every gun covered with a thick coating of yellowish residue that proved nearly impossible to remove. Only more WD-40 would dissolve it, and in one case the silver plating on my collectible second generation Colt 1851 Navy cap and ball revolver was destroyed! Each gun took weeks to clean, because the residue had gotten into all the cracks and tight places and had to be scraped out with tools.

Several years after that experience, I joined an horology club and attended their meetings for about a year. These are guys who fix watches and clocks, and they had one thing to say about WD-40. Don’t ever use it on a clock! They knew all about the yellow coating it leaves, and several members had horror stories about removing it from clock gears. Apparently, not even ultrasound tanks can remove all of it.

Before you rise up to defend WD-40, know that I use it, too. For certain jobs, it can’t be beat. But not for protecting the finish of a gun. Use Ballistol for that.

What does WD-40 have to do with corn oil? Everything. Like WD-40, corn oil dries and leaves a waxy film on anything it comes in contact with. And that’s why it was originally recommended for spring-piston airguns. Not all spring-piston guns, you understand. Just the ones from China.

Duane Sorenson, who used to work at Compasseco in the 1990s, recommended corn oil for all his Chinese guns because of the waxy buildup. He reasoned that the wax filled in the rough machining marks left inside the cheap Chinese compression chambers, eventually building up to the point that compression increased. He was an active proponent of corn oil in spring guns, and I think many thousands of shooters were told by him to use it.

Duane also said the flashpoint of corn oil was very high, so using it would stop dangerous detonations. As far as I was able to test for that, it did seem to work. But — and this is the point of today’s report — corn oil is not recommended for a sophisticated spring-piston airgun powerplant. The current crop of Tech Force guns do not have compression chambers rough enough to benefit from its use.

Time is the criterion
Duane was advising corn oil for airguns like the B3 underlever and the TS45 sidelever. Those guns really did have rough compression chambers that could benefit from a product that infilled their machining marks. But at the same time he was recommending corn oil, Sorenson was also pushing their Chinese manufacturing partner to better finish the insides of their compression chambers. The result was the Tech Force 36 underlever, which was very smooth inside, and later the Tech Force 99, which was even better.

But while this improvement was happening, Duane was still selling lots of the older and less expensive Chinese spring guns that were still very rough. So, he continued advocating corn oil, even as the many of the guns he sold were getting better and had less need for it.

I tested it
Duane was so insistent on corn oil being a miracle-product that I bought a quart of the stuff and began experimenting with it. That was how I learned that it doesn’t detonate. While I was testing it, I was unaware of why corn oil was being recommended and the fact that many of the more modern chinese airguns didn’t need it.

I conducted several tests using corn oil for The Airgun Letter, but frankly I never got the kind of results Duane told me to expect. Part of that was because I was probably testing it on the wrong guns and part was because I wasn’t using it as much as Duane did. I never saw the long-term effects he told me about.

I expected to see an increase in velocity and a decrease in the total velocity variance. The velocity never increased as much as I had thought, but the shot-to-shot variation did decrease somewhat.

What about corn oil today?
This is the reason I wrote today’s report. Do not use corn oil in any modern spring-piston airgun! Corn oil is meant to solve a level of manufacturing crudeness no longer seen in modern airguns. Like many other things, time has changed the game. We no longer put oatmeal in our car radiators to patch small leaks, and we certainly no longer lubricate spring-piston compression chamber with corn oil.

Just as you don’t want a buildup of hard yellow film on the outside of your airguns from dried WD-40, you also don’t want the waxy buildup from corn oil on the inside. Use the products that are recommended for the job, like a proper grade of silicone chamber oil for the compression chamber of your airguns.