I suspect it's due to the fact that TRIARC barrels are gassed for pretty soft shooting but I could not get the bolt to hold open today.  Hooked up the RS AGB to the 12.5 Midlength today to test it out.  TRIARC 15.5 middy, Sprinco white buffer spring and H1 buffer all the way up to G braided beffer spring and H3 buffer and a BCG.  One round loaded into the mag rinse and repeat no hold back all the way up.  Using a 7519 setup with your middy gas tube.  Wooden nickel for your thoughts.

You get an oddball config like a 12.5 middy, and you chalk it's malfunctions up to being "gassed softly".

Aight sport. Or you could use a more proportionate gas system length considering the barrel length...

Midlength was developed for 16 inch barrels

Forgot to mention this was suppressed. EA ARX

Late to the party…


The 12.5 Triarc we played with was significantly under gassed as manufactured. You also need to start with a standard carbine spring and H buffer (step #1). You can play with an H2 if necessary once you get it running, but it’s highly unlikely you’ll need to. Step #2 is to open up that gas port until you get good reliability with your preferred ammo types unsuppressed with the gas around #7-#9. FWIW, all the 12.5” mid barrels we’ve worked with ended up in the scrap pile.

@voodochild , did you ever get this sorted?

@1168RGR I gave up and just put a regular GB on there.

Bummer. Thanks.