For those into competitive shooting, JP Rifles needs no introduction.  For those not familiar with JP Rifles they have been around for a long time making state of the art race gun rifles parts and for AR15s and AR10s.   Today we cover the LMOS BCG and Silent Captured Spring.

When you want to shoot fast,  being able to control the recoil of the gun is a major priority.  If the gun recoils (even on a 223/556) excessively the gun comes off the target and requires time to reacquire for a follow up shot or transitioning to new targets.  There are a few approaches to making the rifle work with you instead of against you.

In an AR you have the recoil pushing the gun back and the barrel up.  If you have a well tuned rifle the difference between it and a stock AR is huge.  The gun just stays on target and you can do double taps and transition a LOT faster.

A few key ways to tune a rifle are:

  • Muzzle brake to control the gas pressure as the bullet leaves the barrel thus reducing both felt recoil and muzzle flip.
  • Reducing the amount of gas being fed back into the gun via an adjustable gas block
  • Going to a rifle length gas system (vs a midlength or carbine gas system). The longer the distance between chamber and gas port the smoother the recoil impulse is.
  • Going to a lighter bolt carrier group as this reduces the reciprocating weight and makes the gun move less.
  • Using a rifle buffer tube and lighter weight buffer/spring setup.

You really need to “tune” all of this together to get it to run reliably. Especially important if you run different ammo and in different environments.

Going to a lighter BCG is a great way to really maximize the gun to run smooth.  Given that they are lighter they require less force to get them to move backwards and thus you need to decrease the gas pressure via an adjustable gas block.  When you do that you can also decrease the spring strength and buffer weight.  The gas slams the BCG rearward, the buffer stops it against the back of the buffer tube and the spring slams it forward.  Obviously, when you get that just right the gun will be moved less and makes for faster target acquisition.

The JP LMOS (low mass operating system) is an example of a well tuned “system” when you run their BCG and the Silent Captured Spring.

The BCG is 2 oz lighter than a standard mil spec unit and is polished to be ultra smooth and the QPQ finish is applied (Quench-Polish-Quench)  This process makes it where the bolt carrier is very, very smooth and extremely hard finish that moves in the gun with less friction and requires less lubrication and also cleans up easier.  I am a big believer in these types of finish and run similar types of finishes in all my rifles.


The Silent Captured Spring is a clever design that does away with the normal spring and buffer.  Instead it uses a “captured” spring/buffer system that features a polished center rod with a buffer weight “stack”.  You can easily change springs to fine tune if you need and they offer a heavy version for suppressed rifles and SBRs with increased gas pressure.   What you notice is really how quiet and smooth it is when you pull and the charging handle.  Very cool and everyone who tries it goes “ooh, that’s NICE”.

JP rifles Silent Captured Spring

JP Rifles complete rifles and parts are definitely top of the line in performance parts.  They aren’t cheap but if you want a gun that runs like a well oiled precision instrument they are worth every penny.

3gun rifle up close

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Founding staff member, avid shooter, hunter, reloader and all around gun geek with an obsession for perfection

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