Dynamic Defense Jet Block MK12 MOD 1 (AEM5/OCM5)

Introducing the JetBlock. A tool-less, two position adjustable gas block. We are huge fans of the AR15 platform, and we all know how badly over gassed they get when used with a high backpressure suppressor. Up until now, adjustable gas blocks had a lot of issues, including gas leak, annoying adjustments, the use of an allen wrench, screws that come loose and carbon locking. The JetBlock is our answer to those problems. Two settings… Regular and Suppressed.

Each JetBlock model includes a two-position adjustment button we call the “GasJet”, tuned for a specific barrel length, and gas system length. This product page is specifically for the MK12 Mod1 barrels. The two-position gas adjustment is tuned specifically for the Mk12 Mod1 paired with the Allen Engineering AEM5 or Otter Creek Labs OCM5 suppressors.

Due to the design of the JetBlock, there is much less gas leak into the atmosphere compared to most gas blocks on the market. The gas block journal and gas tube channel are machined slightly undersized and held to a tolerance of 0.0005″. Installation may require heating of the gas block with a torch, in order for the gas tube and gas block to have the tightest fit possible. In addition to the tight fit, we machine our GasJet to have a tight clearance fit. Due to our design, the JetBlock leaks a lot less than other adjustable gas blocks, which will make your rifle run more efficiently and in theory will also make your rifle quieter.

The JetBlock is for use on barrels that are .750″ diameter at the gas block journal.

The JetBlock is machined from 17-4ph stainless, heat treated, wire-edm cut and treated with a durable QPQ finish. The unit is secured to the barrel by 2 allen head #10-32 set screws. The GasJet can be pinned to your barrel by a gunsmith as an additional installation method, we will not void the warranty if you decide to have it pinned.

Each JetBlock undergoes our multi-step quality control procedure to ensure they are within our tolerances. This step is often overlooked by other manufacturers because it is time-consuming and adds to the cost of the product.

The JetBlock is designed for installation by an experienced armorer or gunsmith.  The JetBlock is compatible with most free-float handguards that can accept a standard low-profile gas block. The JetBlock cannot be installed with standard plastic handguards.

To allow access to the JetBlock adjustment, it can be paired with a handguard which is shorter than the gas block position OR paired with a M-LOK handguard that has seven M-LOK sides, like the Geissele MK16 handguards. It will also work with Geissele MK14 handguards due to the large cutouts at the 2 o’ clock and 10 o’ clock positions. If you can see the top half of the gas block through your handguard slots, the JetBlock will be compatible with your setup.

We have tested our JetBlock with Criterion Mk12 Barrels with a gas port size of .101″, a Colt M16 BCG, Standard carbine H2 buffer tubes with milspec carbine springs. We personally run the BCM Mk2 Mod1 T0 (3.8 oz) buffer system and love it.