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Posted: 2/12/2008 3:46:42 AM EDT
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I am frustrated! Situation: Using RLL on two uppers, 10.5" 6.8SPC & 11.5" 5.56, same lower. Both work fine in SA and both lock back on last round in SA. Both run fine FA with a suppressor. Neither will run FA without a suppressor. Fires one round then nothing. Next round shows dimple from firing pin but will not fire. Rack out round and next one does exactly the same thing, etc. Using a 9mm buffer to slow things down suppressed. I have searched and archived and cannot find anything on this except Ciener bolt bounce....seems like I remember a thread on this or a related subject a while ago. Anyone who can point me to that thread or give some advice on this would be greatly appreciated. This link works fine with 16" or greater barrels. Anyone want to trade a RR for the RLL plus some $$$...I am getting that frustrated!!! Thanks, FH |
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OK, I have an RLL and this issue is NOT related to RLL but F/A in general. What buffer are you running non-suppressed? If using standard buffer, try an H1, if that still bounces then try an H2, if that still bounces try 9mm and so on. I eventually got a MGI RRB as it works with all my calibers (9mm, .45ACP, .223, 6.8, 7.62x39). It is a little pricey but worth its weight in gold. |
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If it runs ok in FA with the 16” barrel I don’t think its bolt bounce. It sounds like a gas problem and the 9mm buffer will make that worse. Try a lighter buffer preferably an H buffer. Are you using the same carrier with all the different uppers? I would not fault the link just yet; I have seen a lot of frustration with getting short barrels to run with R&R guns too.  When it stops running the hammer has dropped “correct” that is what you’re saying  I’m confident someone on this board will help get it running and get all the bugs out.   |
I'm pretty sure it is bolt bounce as what he is describing is classic bolt bounce. The ROF with a 16" bbl will be less than a 11.5" bbl. Slow down the ROF, stop bolt bounce. And I guarantee that it isn't the RLL  |
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Its not the link - works fine in another lower/upper pair that is 9mm dedicated. The 9mm buffer is the two-part 5.6 oz. Works good suppressed just will not run unsupressed in either 5.56 or 6.8. I will try the MGI (ordered one last night) would like the ROF slow-down anyway. Runs about 750-800 RPM suppressed right now w/9mm buffer - would like to get down around 600-650 so maybe MGI will give me that as well as reliable unsuppressed use. NFA is fun but can be frustrating at times! Thanks for the advice (I meant to try a lighter, standard carbine buffer on last range trip but got so mad that I forgot to swap it in....I want a single buffer for this lower that will work with multiple calibers and hope the MGI will fit that bill. FH |
I was thinking the same at first *bolt bounce* until he said it runs with the suppressor. My 11.5” with suppressor increases ROF, unless the extra back pressure from the can is dampening the bolt and stopping bolt bounce.  I would agree the link is probably not the cause. As long as it moves freely and passes the timing check. I have not had any problems running my 11.5 with a H2 buffer, but I will try my 9mm buffer some time just to see what change It makes to the ROF. |
Now that he has given us more info (buffer used both suppressed and unsuppressed), it is a very confusing issue. At first sounded like bolt bounce, but now not sure. I will have to think about this... |
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My S.W.A.G., the fire control group in this particular lower is not timed properly with the RLL. The hammer is being released a hair too soon, causing the light primer hits. With the suppressor installed, the bolt carrier travels rearward faster, the buffer rebounds with a higher velocity, closing the bolt carrier fast enough to beat the fall of the hammer. Karl |
Along these lines, have you done the RLL timing test yet FH? If not (and you don't know the test), put your link in the lower, pull and hold the trigger while you pull the charging handle all the way back and then let go, then release the trigger and then pull the trigger again. If you pull the trigger again and nothing happens then your RLL is properly timed. Repeat a few more times to make sure. Part 2 of the test is to do all the above except instead of pulling the charging handle all the way back, only pull it half way back and then release it. This test should not activate the RLL so when you release the trigger and pull it again the hammer should drop. If this is the case then you have a properly timed RLL. |
An alternative test: With the weapon unloaded, drop the hammer on an empty chamber. keep the trigger pulled and retract the bolt. Slowly ease the bolt home while listening for the hammer fall. If the hammer drops before the gas rings clear the vent holes, the disconnector is being disengaged too soon. If the bolt carrier fully closes and you didn't hear the hammer drop, release the trigger then pull it again while listening for the hammer drop. If the hammer does not drop with the second pull of the trigger, then it probably followed the bolt carrier home. Then something is preventing the disconnector from catching the hammer. If the hammer does drop with the second pull of the trigger, then the disconnector was not disengaged from the hammer. Karl |
you ass, I tried to kill that |
What bug  Hope you didn’t damage your screen  |
Yep, With the link in play, Hold the trigger and slowly walk the CH all the way back forward. The LL should not trip the disco and may find that the bolt may not have totally locked home either. Now while still holding the trigger, pull back on the CH about 3" and let go of it. The B/C charging forward under spring tension should be enough force for the LL to trip the disco. If the hammer releases on a slow CH walk forward, the LL tab is too thick and you need a thinner tab (time too advanced). If the hammer will not trip with the carrier running free from about 3" back, the tab is too thin and you need a thicker tail. Also to point out, since the link has to cam the disco back, it has some dampening effect it's self to help control bolt bounce. |
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OK Range Report (and even more confusing...) Installed MGI buffer & Defender. on 5.56 upper - runs fine suppressed. unsuppressed - acts undergassed - sometimes will not strip next round - other times will not fully chamber next round. Locks open on last round. SA does the same. 6.8SPC upper - suppressed - runs erratically on FA - shoots double & triples - feels like a timing issue on the link - I can work on that. unsupressed - SA only - link will not work but she fires fine. Tested in both uppers with both of the above methods and the link works fine. HELP - I am very close to dumping this link and getting a RR!!! Thanks, fh <----I'm sad now - was so looking forward to a good day.... |
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FWIW, almost the same thing happened with my dias and a 14.5" upper. First I had bolt bounce (one shot, next had primer dent). So, I got the MGI RR buffer thinking I would never again have to worry about the issue. WELL, now it sometimes pulls the next round off the mag, most of the time not until I fire a few singles. Asked here and a few surmised it was an undergas issue. Haven't had time to go out to the range to try the 16" to see if at least it works in that. |
FH - a few things. 1. Have you done one or all timing tests posted? 2. Has your lower been milled to SP1 specsto accomodate forward/back movement? 3. Do you run the KNS Protector? If so, make sure you either removed material off the rear lug OR had more material milled out of the rear-bottom of the lower. The KNS Protector will bind on the lug causing sporadic problems with RLL function. This happened to me until KNS explained the issue and fix to me. Now onto your gas issue. Can you remove the FSB? If so, use a pin gauge or drill bit shank to measure the gas port for both uppers and report back. This will tell us if you uppers gas ports are undersized. If possible, I would try another lower (just for shits and giggles) and what are the MFG of the uppers? |
Thanks for the advice - back to the shop then to another range session possibly next Sat! Thanks all, FH |
Running a heavy buffer and extra power spring will turn a perfectly functioning M16 into a single shot unless you have some severe overgassing issues. |
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