Why PopStop and why does FRP (First Round Pop) matter?

Silencers are subject to the laws of physics and fluid dynamics just like everything else. Hiram Maxim’s original firearm silencer did a terrific job at reducing the jarring impulse noise of rapidly expanding propellant gasses entering the atmospher. How? His silencer slowed the propellant gas down to the point where the gas did not enter the surrounding atmosphere all at once. This same principle exists today with modern silencers. Modern silencers, like Maxim’s original silencer, are essentially still hollow tubes with chambers constructed as baffles or monocores. Most modern suppressor have blast chambers – the area where propellant gasses enter first after leaving the barrel. Being that blast chambers are hollow they are filled with air in a dormant state. The oxygen content of air is approximately 21%, and when this air contained within the blast chamber and the rest of the silencer comes into contact with hot propellant gasses the oxygen content acts as an oxidizer and can create an audible and visible reaction. The audible reaction is called First Round Pop (FRP) and the visible reaction manifests as a flash outside of the silencer and is called First Round Flash (FRF)

Most all suppressors experience the effects of FRP to varying degrees. However suppressor designs that incorporate baffle designs rather than monocore designs tend to exhibit less FRP. Additionally suppressors with larger blast chambers will tend to have louder FRP as the greater internal volume allows for more air. FRP matters because often times when silencers are use one shot needs to be taken. If silencers are used primarily to reduce sound and muzzle flash then measures can be taken to make them as effective as possible.

Some steps to mitigate FRP include:

  1. Water – Advantage (cheap, plentiful) – Disadvantages (messy, corrosive, is not supposed to be used in rifle cans)
  2. Wire Pulling Gel – Advantage (can be effective) – Disadvantage (messy, relatively difficult to apply)
  3. RemOil  – Advantage (can be effective) – Disadvantages (messy, expensive)
  4. Lithium Grease  – Advantage (can be effective) – Disadvantages (messy, relatively difficult to apply)
  5. Ultrasound Gel – Advantage (can be effective) – Disadvantage (messy, expensive)
  6. Canned Air – Advantage (can be effective, relatively easy to apply) – Disadvantage (comes in larger containers, requires placing hand over muzzle of chambered round for use)
  7. Cigarette/cigar smoke – Advantage (can be effective) – Disadvantage (requires putting mouth in line with muzzle)
  8. dB Foam – Advantage (can be effective) – Disadvantage (expensive, messy, comes in large container

And then there is PopStop, the first commercially available device designed specifically to eliminate first round pop and first round flash in silencers. PopStop is a machined titanium accessory that facilitates the injection of CO2 into the blast chamber of silencers which temporarily displaces oxygen – the main cause of first round pop and first round flash.

PopStop interfaces between barrel and suppressor and utilizes a valve that allows for an injection of inert carbon dioxide into the suppressor via commonly available carbon dioxide cartridges and handheld tire inflators. The result is a suppressor purged of oxidation gas (oxygen) and replaced with an inert gas (carbon dioxide). We’ve tested the effects of PopStop lasting up to five minutes with a one second injection. The effects can last even longer if a condom (or similar) is used to seal the end of the suppressor post-injection.

Using a calibrated Larson Davis LxT-1 sound impulse meter our testing yielded a reduction of up to 9 dB by utilizing PopStop. Additionally, PopStop eliminates suppressor flash associated with FRP and can act to cool down the suppressor which helps reduce the POI (Point of Impact) shift commonly observed with certain suppressors.


PopStop is available here in either 1/2-28 or 5/8-24 and comes included with a CO2 inflator, cartridges, condom, and color coded shim kit.


Indonesia: PT Pindad SS2-V7 Subsonic

SS2 V7

SS2 V7 Subsonic

On June 9th, 2016 the state-owned Indonesian defense company PT Pindad launched four new small arms systems. Included was a new rifle named the SS2-V7 Subsonic. This new rifle is based on the standard issue SS2 which was introduced to the Indonesian military in 2006. The SS2 is an entirely Indonesian designed weapon and was developed to replace the SS1 which was a licensed copy of the Belgian FN-FNC. The SS2 uses a gas piston design similar to the Kalashnikov.


Pindad SS2

The SS2-V7 Subsonic appears to have a much shorter barrel with a larger suppressor attached at the muzzle. No details yet have been released about the ammunition but the rifle appears to be chambered in 5.56. Shooting a subsonic 5.56 round in a standard AR-15 platform requires the need to cycle the action manually due to the lighter load not being able to throw the BCG far enough to eject the spent case and pick up another round. Some modifications with springs and gas systems have been attempted in an effort to get the Ar-15 to cycle reliably using subsonic ammunitions and these modifications have been met with varying degrees of success. The modifications will invariably require a heavier than normal projectile to increase gas pressure. No word has been given yet as to the type of ammunition the SS2-v7 would use but assuming a 75 Grain bullet you can expect the following trajectory numbers (Courtesey of JBM Ballistic Calculator):


Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
0 -1.5 *** 0.0 *** 1052.2 0.942 184.3 0.000 0.0 ***
100 -0.0 -0.0 0.0 0.0 993.7 0.890 164.4 0.294 51.7 49.4
200 -33.7 -16.1 0.0 0.0 946.5 0.848 149.2 0.603 106.2 50.7
300 -106.1 -33.8 0.0 0.0 906.4 0.812 136.8 0.927 163.2 52.0


The table shows a trajectory numbers that are similar to a subsonic 300AAC bullet, however energy delivery tells a different story. Energy at the muzzle is at best equivalent to a standard FMJ 380ACP round. This is less than half the energy delivery of a standard 300AAC cartridge. For close in operations a suppressed SMG like the MP-5 SD may be a be better choice. However, this setup might be a good choice if an entry team member is carrying magazines loaded subsonic and supersonic which could easily be switched out after taking out sentries and/or lights in a stealthy manner.



SS2 V7 Subsonic




From Russia with Love: Lobaev Arms DVL-10 Saboteur

Lobaev Arms DVL-10 Saboteur


The Lobaev Arms DVL-10 Saboteur is an integrally suppressed sniper rifle system that is designed for relatively close ranges. Along with standard 308 Win, the DLV-10 uses a new proprietary cartridge called the 40 Lobaev which sends a 419 grain bullet at subsonic velocities. At 1017 fps the muzzle energy works out to 962 ft/lbs which is significantly more energy that even 338 Lapua subsonic, which at 1000 fps pushes a 300gr projectile with 666 ft/lbs of muzzle energy. This is very impressive even with significant bullet drop occurring past 100 meters. See below for chart courtesy of JBM Ballistics:

Calculated Table
Range Drop Drop Windage Windage Velocity Mach Energy Time Lead Lead
(yd) (in) (MOA) (in) (MOA) (ft/s) (none) (ft•lbs) (s) (in) (MOA)
0 -1.5 *** 0.0 *** 1018.5 0.912 965.0 0.000 0.0 ***
100 -0.0 -0.0 0.0 0.0 976.8 0.875 887.6 0.301 53.0 50.6
200 -34.9 -16.7 0.0 0.0 941.1 0.843 823.9 0.614 108.1 51.6
300 -109.1 -34.7 0.0 0.0 909.6 0.815 769.7 0.938 165.1 52.6
400 -225.2 -53.8 0.0 0.0 881.3 0.789 722.5 1.274 224.2 53.5
500 -386.2 -73.8 0.0 0.0 855.3 0.766 680.5 1.620 285.1 54.4
600 -594.8 -94.7 0.0 0.0 831.3 0.745 642.9 1.976 347.8 55.4


According to their Facebook page Lobaev Arms is a Russian manufacturer of high end precision rifles and was founded in 2005 and is located in Kaluga which is 150KM southwest of Moscow. They purport to be suppliers of sniper rifles to Russian security services which may be unprecedented for a privately operated company operated in Russia. The Russians have a history with using subsonic ammunition in accurized platforms. The VSS Vinorez, which is in service with the Russian armed forces utilizes the 9×39 cartridge.  I’m not holding my breath for these to be imported into the US for civilian sales, however the 40 Lobaev would be an excellent choice for those needing a subsonic platform and require the additional energy delivery at close ranges.



  • Precision – 0.5 MOA\15 mm distance between the centers (5-shot at 100 m)
  • Maximum range – 600 m
  • Muzzle velocity – 315 m/s
  • Operating temperature range – -45+65 C
  • Caliber – .40 Lobaev Whisper \ .308 Win (civil)
  • Length – 1004 (730 with folded stock) mm
  • Height – 226 mm
  • Width – 62 mm
  • Weight – 4100 g
  • Barrel length – 400\600 mm (civil)
  • Trigger pull – 500-1500g
  • Bolt handle – right
  • Bolt action – right
  • Magazine – 10 rounds

Standard package:

  • Barrel contour – special contour
  • Barrel length – 500mm
  • Caliber – .40 Lobaev Whisper (308Win – civil version)
  • Bi-pod – none
  • Suppressor – LIS
  • Scope mount – STD Picatiny rail