JR Machine Products – Corn Cob Solvent Trap Review Part 1

JR Machine Solvent Trap
JR Machine Products – Corn Cob Solvent Trap Review Part 1

U.S.A.-(AmmoLand.com)- Despite recent legal battles between John Q Public, solvent trap manufacturers, and an overzealous ATF, I’ve decided to wade into a brief review article of JR Machine Product’s Corn Cob solvent trap.  My thoughts and opinions on the ATF will wait for another article, this one’s all about the product, at least as far as possible.

What exactly IS a solvent trap?  It’s all in the name.  A solvent trap is a device that attaches to the end of our barrels in an effort to trap and contain solvents used while cleaning our guns.  While many of us have haphazardly splashed solvents around for years, the fact is that these abrasive chemicals have a number of negative health effects.  These can include cognitive impairment, memory loss, and even carcinogenic effects.

JR Machine Solvent Trap
What comes in the box. Tube, cups, endcap.  No center markings or dimples, which the ATF contends would make this a suppressor instead of a solvent trap.

Many know solvent traps for their other use, which has been as the base for a Form 1 (read: legal DIY) suppressors.  Recent ATF actions have complicated this matter, saying that buying any parts intended to be used for a suppressor, even if not assembled until after Form 1 approval, constitutes buying actual suppressor parts that should have individually been Form 4 (dealer to buyer) transferred.

It is important to note that JR Machine does not advertise this as a “Form 1 kit” or imply any use beyond the gathering of solvent.  They have no control over what the end user may choose to do with this, but JR Machine wants this to be clearly stated, which is fair to do.

Every solvent trap that I’ve seen has been cylindrical in shape, has cups inside for the collection of solvents, and affixes to the barrel either via direct thread, or using a quick-detach mount machined into a muzzle device such as a flash suppressor or muzzle brake.

JR Machine Solvent Trap
SilencerCo’s ASR Bravo mount and Single port Brake.

Looking at Jr Machine’s 6″ Corn Cob kit, here are the tech specs:

  • 1.5×6″ Corn Cob – 1.5″ machined internal spacer
  • Tube – Grade 9 Titanium 1-7/16×20 threads on one side 1-3/8×24 on the other
  • Internals – (2) 17-4 H900 SS, (4) Grade 5 Titanium OD 1.355” Face diameter .400”
  • End Cap – Flash hider end cap

Does the Corn Cob look familiar to you?  If you were involved in, or paid attention to early GWOT military equipment, it likely will.  Drawing some close aesthetic parallels to KAC’s NT-4 suppressor, the Corn Cob takes it’s name from the NT-4’s nickname.

The JR Corn Cob attaches to the barrel either via a direct thread mount adaptor, or using SilencerCo’s ASR (Active Spring Retention) pattern mounts.  The 6″ Corn Cob only has room inside for the single port brake to be used, while the 8″ Corn Cob has an additional .5″ of space to work with.

JR Machine Solvent Trap
Single Port Brake meets ASR Bravo mount, which provides secure lockup with the tube.

With a product that’s designed for the simple task of catching liquid dribbling out the barrel, the primary metric we can judge by is it’s build quality.  How precise is the machining?  How evenly was cerakote applied?

In this I can say that JR Machine has absolutely outdone itself.  The the titanium tube is showcase worthy, with a perfect layer of cerakote covering the wrapped titanium tube.  The internal cups (which rest on a built-in spacer within the tube) are smooth, free of burrs or rough edges left over from the machining process and stack in as perfectly straight a line as man can make it.

JR Machine Solvent Trap
Cups, clean as Granny’s fine china.

The front endcap of this solvent trap unthreads, allowing the internal cups to be pressed out the front.  Starting from the rear, the two larger cups are made from 17-4 H900 stainless steel, while the remainder are Grade 5 titanium.  Once the stack is slid back into place and the endcap threaded back on, there is absolutely no play or wiggle room.

JR Machine Solvent Trap
Machined spacer shown inside the tube.

Using SilencerCo’s ASR mounting system for this solvent trap was a deft choice.  The system has been adopted by a number of other manufacturers, is well known, has mounts widely available, and will have greater aftermarket longevity due to its non-proprietary design.  SilencerCo was kind enough to send out a discounted ASR Bravo adaptor and a single port muzzle brake mount for this article.  The ASR Bravo screws into the Corn Cob tube and stays there.  Once the Cob is screwed onto the threads of the muzzle brake, the Bravo has a small locking ring you twist to make certain it stays where you left it.  Whether used on solvent traps or suppressors, the ASR mount is a well-built system.

JR Machine Solvent Trap
Once your Corn Cob is screwed on, go ahead and clean your barrel out with whatever abrasive solvents you like using to scour copper fouling and carbon out of your lands and grooves.

Once your Corn Cob is screwed on, go ahead and clean your barrel out with whatever abrasive solvents you like using to scour copper fouling and carbon out of your lands and grooves.  The Corn Cob will be there to catch all the liquid leak-free, so you can dispose of it where and when you’re ready.

JR Machine Solvent Trap
The JR Machine Corn Cob kit as shown runs $440-$509, and has multiple options for cerakote color and cup porting.

The JR Machine Corn Cob kit as shown runs $440-$509, and has multiple options for cerakote color and cup porting.
In Part 2 I’ll be discussing the currently murky waters of the National Firearms Act and Form 1 suppressors.
Stay tuned!

About Rex Nanorum

Rex Nanorum is an Alaskan Expatriate living in Oregon with his wife and kids. Growing up on commercial fishing vessels, he found his next adventure with the 2nd Bn, 75th Ranger Regt. After 5 tours to Afghanistan and Iraq, he adventured about the west coast becoming a commercial fishery and salvage SCUBA diver, rated helicopter pilot instructor (CFII) and personal trainer, before becoming a gear reviewer and writer.”

Edited to add:  Hi reddit 1/23/23

Jens Hammer

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Thats a lot of cash and high strength material with GWOT muzzle attachment parallels just to prevent bore cleaner from dripping on the floor. I use a discarded plastic pop bottle and electrical tape to catch patches and dribble at near zero cost. As for suppressors, I think they should be sold without registration and punitive taxation, along with SBR’S. I see kits like this as smoke signals to the Feds. No one with a functioning brain stem buys these for solvent catching. No one. Hell, the ATF wolves are chasing buyers of real fuel filters from China, these are… Read more »


And the salivate all over themselves while getting ready to pounce on an innocent person owning a fuel filter for their pickup or car.


Right on, someone in OreGONEISTAN to be proud of. Bet where he lives isn’t portland.


R-I-G-H-T, and NOBODY shoulders those gay braces for the “handicapped” either. Solvent traps, bump stocks, binary & FRT triggers, their purpose is all the same: to “go fast & quiet”. The ATF have proven themselves NOT to be geniuses, but “COMON MAN!!!”…