Run 'Em Dry

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Do piston systems run when de-greased? Well, there’s one way to find out.


Gun Test #3: De-Grease the Pistons

The sand hadn’t gotten me anywhere in the previous AR-15 torture test, so I decided to pile on. Since most of the rifles were piston-driven, I figured I’d really create problems: I degreased the piston system. That way, they’d be running bare, dry metal on metal, and the sand could do more.

I used carb and choke cleaner to thoroughly degrease all the piston parts. I didn’t degrease the bolt, carrier and trigger mechanisms simply because of my earlier test. A properly set-up AR will run dry in the right conditions. But dry is not how it is meant to run. If I were to degrease it entirely, I’d have to (in the interest of proper scientific method) do three AR-15 torture tests: dry bolt and carrier, lubed piston; dry piston and lubed bolt; and both dry.

Again, there is only so much one experimenter can do, so I left that level of thoroughness to someone else. I also did not degrease the gas tubes of the DI guns. Once de-greased, they all got the sand tests all over again.

AR-15 Torture Test Result: How did it go? To summarize in one word: bo-ring.

Dumping It On

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Overloading the piston with oil.


Gun Test #4: Too Much Lube

Since the sand on dry piston systems had proven an utter failure (heck, all the AR-15 torture tests to this point was a failure, if the goal was to create malfunctions), I figured to go in the opposite direction: Too much lube.

My first attempt was ugly in the extreme. I figured I’d just pour 10W30 motor oil out of the bottle directly onto the piston system.

Oh that was awful. Bad decision. Not the thing to do. You see, there was no way to pour just through the holes in the railed handguard, oil oozed all over the handguard itself, and so I ended up with a piston-driven oily mess. Everything forward of the magazine well was a sloppy, oily mess, so much so that I didn’t want to fire it. I didn’t want to touch it, let alone let it splatter me with oil.

So, I used three cans of carb and choke cleaner getting that one rifle cleaned, plus a few vigorous swishing sessions in the club’s drainage pond (we call it the rice paddy), to get it un-obnoxioused. Once clean, I used a proper oil can, pumping oil into each piston system through the holes of the railed handguards, and gooped them up good.

Once gooped, they received the sand treatment again. Each got the five rounds, dropped, shoveled, five rounds and repeat. Each proved to be up to the task, grinding through the ammo, sand and my patience. I wore a facemask for this and an old shirt. I realized, from the sand splatter in tests two and three, that there was a lot of stuff flying about, and I didn’t want any in my eyes.

AR-15 Torture Test Result: In the continuing pattern, this was an utter failure, except to turn even more club members away from the range in agony, and add evidence to my lunacy.

Introducing the MGA Banshee Tactical Rifle
What Killed the Bren Ten?
Patrick Sweeney is the author of many of Gun Digest books' best-selling titles, including Gun Digest Book of the 1911, Vols. I & II; Gun Digest Big Fat Book of the .45 ACP, Gun Digest Book of the AR-15, Gun Digest Book of the AK and SKS, Gun Digest Book of the Glock and Gunsmithing: Pistols and Revolvers, among other titles. A master gunsmith, Patrick is also Handguns Editor for Guns & Ammo magazine.


  1. I am a LH shooter in the market for a mid level AR . I would like to find something in a 308 so I could also use it to deer and hog hunt . What are your top choices and what to stay away from as well !
    Thanks for your help !
    Scutt Dog