SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs

by Pete
SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs

Good afternoon everyone and welcome back to TFB’s Silencer Saturday brought to you by Yankee Hill Machine, manufacturers of the new YHM R45 Multi-Host Suppressor. Last week Austin R. brought us a very special look at the B&T MK23 pistol suppressor. This week we return to one of my greatest loves, suppressing 300 Blackout subs with the SIG Sauer MCX SPEAR-LT rifle and suppressor platform. Whether you are a long-time fan of 300BLK or you are just trying to decide if you are going to make the jump into this suppressor-born cartridge, stick around for a little light reading.

SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs
More SIG MCX and 300BLK @TFB:
Firearms, suppressors, and ammo used in this review:

SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs

SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs

Just so you know, there isn’t going to be an earth shattering reveal in todays review; these are all things I have stated a few times in the past. But it has been too long since I have spent some quality range time with one of my overall favorite platform and suppressor combinations for the 300BLK cartridge. The SIG MCX rifles and pistols are in their third generation known as the SIG MCX-SPEAR LT. The original SIG MCX, and the second generation SIG MCX VIRTUS have been replaced with the lighter and more feature-rich SPEAR-LT lineup. The popular and ultra-compact SIG MCX Rattler PDW is the only remaining pseudo-VIRTUS model still in production.

I know you are all going to ask about the SPEAR-LT handguard observations across social media over the last few months. After torquing my handguard screws tighter than they were from the factory, I haven’t seen any measurable movement after at least a dozen range sessions. I did mount the ATIPAL-C IR laser on the MCX-SPEAR LT which happened to line up perfectly with the junction between the receiver and the rail, adding additional rigidity and I have confirmed my zero with the visible laser on a few occasions. Full disclosure, I am running an older VIRTUS barrel in the SPEAR LT upper receiver.

But as much as I love the MCX, this is Silencer Saturday and I wanted to talk more about the SIG SLX and SIG SLH suppressors. The previous generation of SIG rifle suppressors were the SIG SRD line which featured a tubeless design and were available with a QD mounting system. To this day, the SRD762QD-TI is still one of the quietest suppressors for 300 Blackout subs to my ears.

SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs

The latest generation of SIG rifle suppressors is broken down into two categories (SLX and SLH) with a variety of material, length, and mounting subsets under each one. The SIG SLX suppressors are designed to achieve a maximum amount of blowback reduction while providing signature suppression under extreme conditions. The SIG SLH suppressors balance the maximum amount of noise suppression with blowback reduction to mitigate toxic gases and maintain weapon reliability. In the most simplistic terms, hard use and supersonic rounds = SLX; maximum quiet and subsonic rounds = SLH. It’s not that cut and dry, but you get the picture.

I wish the naming conventions were a little more clear, but there is also a reason that I am not in product marketing.

There are four main attributes of the SLX and SLH suppressors.

Monolithic Core – Additive Manufacturing

The use of additive manufacturing to make suppressors gives engineers the ability to create geometries that were not possible with traditional machining.

Forward-Flux Reduced Blowback Technology

Venting gasses forward and out of the muzzle end of the suppressor drops the pressure inside the tube which reduces the amount of gas blowback down the barrel and into the action. Excessive blowback can send toxic gasses towards the shooter and can effect the cyclic rate of the weapon, possibly causing malfunctions.

Clutch-LOK QD Mounting System
SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs

The Clutch-LOK system is one of the best on the market, providing the user with a simple, quick, and solid attachment system. It would be nice if the QD system were smaller and lighter, but it does work.

Flash-Lite Signature Reduction

This is one of the features of the SLH and SLX suppressors I have been meaning to test more fully in low light situations. But having used all of these suppressors on a variety of barrel lengths, with a variety of ammunition, I have yet to see any noticeable flash.

So, Which SIG Suppressor For 300BLK Subs?

SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs

At the risk of sounding like a double platinum broken record, the suppressor that you buy should be the suppressor that fits your needs. If that need is shooting 300 Blackout subs as quietly possible, the SLH300TI-QD or the direct-thread SLH300TI is your best bet.

For one, the SLH300TI is extremely quiet. On the 9″ MCX-SPEAR LT, the SIG SLH300TI-QD with subsonic 300BLK ammo allows you to hear the action cycling, the bullet hitting the cardboard target. and the ability to leave the additional hearing protection in the bag.

SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs

While not exactly short or feather-lite, the nearly 9″ suppressor weighs in at a respectable 16 ounces. In fact, it doesn’t feel like it weighs 16 ounces (it does, I put it on the scale). The direct thread version is about two ounces lighter. The Inconel versions add unnecessary weight for a silencer that will be used predominantly for subsonic 300BLK. So for its length, the SLH300TI is perfectly light enough for compact carbines.

The difference between the SLH300QD-TI and the SLH762QD can be measured in decibels (it is quieter) but it should also be measured in ounces. The Inconel version adds slightly more than five ounces and my feeling is that it is a hard use suppressor better suited for supersonic 300BLK or 7.62×51 on short barreled rifles.

SIG doesn’t publish MSRPs for suppressors, but a causal search of the known internet revealed an on-the-shelf price of $1,249 with discounted pricing listed below $999. Like the weight of the QD system, the prices of the SLH and SLX models, especially the titanium versions could be better. But they do fall into the upper middle range and not the top of the range of other market options.

SILENCER SATURDAY: Why, Hello SIG MCX And 300 Blackout Subs

I still cherish my SIG SRD762TI-QD with subsonic 300BLK on the MCX, but even with the added weight, the SLH300TI-QD may surpass it in sound performance. Which is a notable achievement.

Have a great week. Be safe, have fun, and we’ll see you back here next weekend for another Silencer Saturday.




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Join the conversation
  • Aono Aono on Sep 24, 2023

    Pete can the MCX 300 9” cycle subs without a can? I’m considering one, but for use with a very low backpressure suppressor.

    • See 3 previous
    • Aono Aono on Sep 25, 2023

      @USMC Grunt2 Ok, good to know, thanks. The Flow is higher backpressure than the HX-QD so that does seem promising.

  • Predrag Djuric Predrag Djuric on Sep 25, 2023

    A very interesting rifle and suppressors.