Before the use of LIDs became standard, people did all sorts of muckymuck to get their suppressed pistols running. It wasn’t uncommon to reduce recoil spring weight drastically, which often came with its own issues regarding pistol functionality. Pistols with fixed barrels don’t require boosters and any amount of extra weight on the muzzle doesn’t have an effect on function. Similarly, pistols with a falling locking block design such as the Beretta M9 normally do not require Nielsen Devices because the barrel travels in-line with the bore.

Term: Nielsen Device

Also Known As:: Linear Inertial Decoupler (LID), Recoil Booster, Muzzle Booster

Relates to: Suppressors/Silencers

Category: Tactics and equipment

Application(s) of Use: To ensure reliability of suppressed pistols that use a tilting barrel.

Definition: An attachment that allows a pistol to properly cycle when the weight of the suppressor is added to the end of the barrel.

Why it Matters: Pistols with a Browning tilt-barrel design will – you guessed it – tilt the barrel upward as part of the cycle of operation. This design is used in the majority of modern pistols such as Glock, M&P, Sig Sauer, HK, CZ, and too many more to count. When the weight of a suppressor/silencer/muzzle muffler is added, quite often it can prevent the pistol from properly unlocking or cycling.

Into the Weeds: 

If a suppressor is sufficiently light enough, such as a teeny Gemtech Aurora, even with a tilt-barrel design a LID most likely won’t have to be used.

Though there are a handful of different designs, most modern boosters consist of a piston, spring, and housing. Some pistol silencers have integral boosters while others have removable boosters.

Usually the pistons themselves can be swapped for different thread pitches for use on different handguns. The boosters allow the expanding gas inside a silencer to push the entire suppressor forward, thus temporarily relieving the extra weight on the end of the tilting barrel and allowing for normal operation. The animated gif below isn’t perfect, as it shows the silencer body as static, but it should give you a decent idea of how it works.

In Summary, Nielsen Devices simply allow for more reliable suppressed operation with most modern pistols.