Recoil|January - February 2021
The JK Armament SBR PRO “Solvent Trap” and the Bad-Idea Oil Filter
Dave Merrill

Just like nearly everything else in this issue, we went the DIY route with our silencers. Normally when you purchase a suppressor, it’ll sit at your dealer for months — sometimes more than a year — before the federal government approves your paperwork. But it’s faster if you make your own; in fact, we did just that in RECOIL Issue 46.

“Solvent trap” is the current underground moniker for parts and kits used to manufacture your own silencer with an approved Form 1. These are perfectly legal in most jurisdictions, provided you haven’t drilled holes in anything just yet. Why would you want to fill out a Form 1 instead of a factory Form 4 transfer? Time, mostly. As we write these words, an online Form 1 takes an average of three weeks whereas even the fastest Form 4 transfer now sits between three and four months. Cost savings is another measure, as most solvent trap kits are available at a significant discount relative to factory silencers (invariably for a reason).


We’ll get the only-worth-it-for memes alternative out of the way first: the oil filter adapter.

About a decade ago, we first laid eyes on oil filter adapters; they were originally made by Tom Cole of Cadiz Gun Works and called “solvent trap adapters.” Cole tells us, believe it or not, that the original intention was to actually trap solvents. Later, they released their Econo-Can, a registered adapter that’s transferred like a standard silencer.

But this type of filter being featured in the 2019 release of Call of Duty: Modern Warfare really brought them into the world of mainstream memes. While you can find sketchy adapters on Amazon and Wish, Cadiz Gun Works actually manufactured and legally registered oil filter adapters as silencers and even have an oil filter replacement service for when they wear out.

We teamed up with an SOT to legally register our own. Engraving actually took more work than we anticipated because our adapter didn’t have enough surface area. A stainless steel washer was welded to the base for this purpose.

So, how effective is it? Setting aside that it makes most pistols a singleshot affair because there’s no way to attach a booster, the ungainly size that blocks sights on both rifles and pistols and the massively increased weight, simply put: It’s not all that quiet. An oil filter silencer essentially is a simple expansion chamber that works for a few shots before having to be replaced. And the larger the bore, the faster it loses any efficacy.

And oh yeah — you can’t even legally swap out that oil filter unless you’re a manufacturer.

In a world where silencers are OTC just like a receiver, rifle, or pistol, these oil filter silencers would make for a fun party trick, similar to taping a soda bottle to the end of your .22LR. But since legally manufacturing or purchasing adds on $200, and you can’t even swap the filter yourself? Hard pass.


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