The JRC buffers and tubes have gone through some changes over the years.  This article will describe the various styles you could come across in your travels and differentiate them with the current shipping design.

JRC Specifics

Background:  In the early days of JRC, there was a push to be as compatible with AR style weapons as possible for cost reasons (why re-invent the wheel) and for interchangeability.  While this was a noble goal, it was ultimately impractical for a direct blowback design weapon.  

Solution: Our buffers are larger to accommodate the lack of lockup in the design.  This in turn requires a longer than standard buffer tube, which is why our tube CAN differ from a standard AR tube.  I say  “CAN” because in certain configurations, a regular commercial or Mil-Spec tube will work if the right sized buffer is in place. More on this at the end of this article.

 Most configurations shipped since 2014 with the custom longer tube.  Our tube is ~9″ overall length internally while a std. AR tube measures ~7.5″. We moved to a Mil-Spec sized tube during 2020 as the commercial spec tubes were getting harder and harder to obtain and the world seemed to prefer Mil-Spec, so we switched.

The manual goes into a detailed description of spacing and why it is important to maintain when working on the firearm.  This also comes into play when changing calibers.  The Caliber conversion kit will come with a buffer and spacers.  These may or may not need to be changed out depending on what your current configuration is, and what you are moving to.

The one thing that will NOT come with your conversion kit is a tube.  This is why it is important to understand what you have currently, what is required and what is possible with the right combination of parts.

Caliber Tube Inside lengthSS Buffer lengthSpacer / bumper 
9mm Pistol or rifle7.5″ ***3.75″ plain1.25″
9mm Rifle9.0″4.75″ plain1.25″
40S&W/45 ACP Rifle9.0″4.75″ lead filled1.25″
10mm Rifle9.0″5.25″ lead filled0.625″
Current JRC Buffer / Buffer Tube configurations

*** *** 9mm should be the ONLY caliber with a buffer / buffer tube combination in this configuration. 40 S&W and 45 ACP calibers MUST have the 9” long tube and the 4.75” buffer at a minimum. 10mm requires use of ONLY the JRC 9” tube with the 5.25” long buffer


Do NOT substitute a std. AR 15 spring or buffer system into your JR Carbine EVER! It will not work. You will damage the gun and you will not be covered under warranty!

If you shoot competitively and want to try a custom buffer system, it may or may not work. JRC will not support aftermarket systems added to the firearm. Be aware that you are voiding any warranty if you attempt this.

Our only suggestion is if you want to shoot lighter loads (handloads void warranty, FYI), you could switch out a 9″ tube for a std. AR 7.5″ tube and acquire a pistol buffer (3.75″) to lessen the mass and the chance of short stroking. However, you still have to maintain the spacing in the back of the tube with a spacer and still need the JR specific spring.

*** This custom configuration will work fine in the JR Carbine, but not be covered under warranty if you use handloads. Regular 115 gr ammo will cycle just fine with the pistol buffer configuration. +P, 124 gr or 147 gr will probably be too hot for this lighter buffer but your mileage may vary. If you get misfeeds with this setup running these ammo types, we suggest going back to the heavier buffer and longer tube.