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Posted: 6/18/2026 2:09:18 PM EDT
[Last Edit: TyrannyOfTheMinority][Edited]
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Hello fello RLL enthusiasts : ) I've been running my RLL successfully in a Fightlite/Ares Defense MCR for many years at this point. I have the link set up with Quarterbore's modified burst FCG setup and it has been successful for many a range day. I use both suppressed 12.5" barrels (low gas setting) and unsuppressed 16" barrels (normal gas setting) on the gun. Just recently, the gun has begun doubling on the semi setting. Not on every trigger pull, but say about 20% of the time. Seems like the hammer is releasing on trigger reset. I cannot reliably reproduce it to isolate the issue. However it ONLY occurs with the unsuppressed 16" barrel on normal gas. It does not happen with the suppressed/low gas barrel. Full auto/link function works as expected. I cannot for the life of me figure out how the barrel/gas would be influencing the function of the FCG and RLL at all, let alone only in semi. Any guesses on what's happening here? My best idea is to just replace the disconnectors - maybe the mating surface(s) with the hammer have been worn down at this point. Paging @amphibian, @jbntx, @esox, @circuits and the other resident RLL experts whom I'm blanking on at the moment! |
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Paddle thickness and timing have been unchanged for several thousands of rounds at this point (5k-ish). I run Quarterbore’s timing test before every range trip. It passes with hammer drop at a consistent point in the BCG travel. Link has run smoothly in this host for years with all barrel configurations. Just recently - independent of any timing or paddle changes - has this doubling issue appeared (on the long bbl/normal gas). |
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Mechanically it sounds like the semi-auto disco isn't reliably holding onto the back of the hammer spur. When this happens and the disco only has say 50% grip on the rear of the hammer spur when you let go of the trigger the disco release the hammer before the nose of the trigger is in engagement with the trigger ledge on the underside of the hammer. This is the same effect you get when folks used to make "homemade" binary triggers by grinding off the nose of the disco which then lets the hammer fall as the trigger is released as the disco lets go of the hammer spur before the nose of the trigger engages the underside of the hammer engagement ledge. As to why the disco isn't 100% engaging the hammer spur can be due to a couple of reasons. 1. The disconnector spring is worn out and the disco isn't able to properly grab hold of and hold onto the hammer spur. This is usually a pretty easy solution to just put a fresh mil spec disco spring on the semi-auto (left side) disco. 2. The RLL is ever so slightly impinging on the semi-auto disco. On a RLL select fire group the left side semi-auto disco needs to be relieved so that the RLL can't ever touch it. I have seen semi-auto/left discos not 100% relieved properly and/or somebody relieved the back of the rear lug pocket and this allows RLL makes ever so slight contact with the left/semi disco partially disengaging it from the hammer. This can present as an issue when somebody installs a KNS protector changing the engagement angle of the RLL, over relieves the rear lug pocket allowing the disco to cam rearward farther than necessary, and/or running an upper with a more high speed bolt carrier and/or stronger recoil (like an MCR) where that little bit of engagement of the RLL on the Semi Disco used to not be an issue with a slower DI upper but with a higher speed bolt carrier slamming home harder it imparts enough energy into the disco slightly disengaging it. When you release the trigger it then lets the hammer go. I would check to see if there is any way your RLL can make any contact with the left side disconnector when the trigger is pulled back and the link is pulled all the way to the rear of the rear lug pocket. It it looks like it could touch the left/semi in any way you need to relieve the interior disco more. You could also test to see if your host doubles on Semi by removing the right side full auto disco, put a spacer/washers in place of the full auto disco and then run the gun with just the left side semi-auto disco and no RLL installed and see if the doubling symptoms goes away. If it does than that means your RLL is somehow engaging the semi-auto disco and slightly dislodging it off the hammer spur. If the doubling persists with the right side full auto disco and RLL removed than you know its something worn with the hammer, left disco, or left disco spring. (usually just a worn disco spring) Good luck and hopefully its an easy fix. |
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Thanks for the input guys, most especially JBNTX's in-depth discussion. My link is well clear of the semi disco - no contact whatsoever. Hopefully it's as simple as a worn disco spring. That's much easier to deal with than a worn surface making poor contact with the hammer spur (which was my initial thought). I've replaced the semi disco spring - now just gotta make it back to the range for test fire. Will update with the outcome - thanks again! |
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