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Posted: 6/28/2025 11:24:46 AM EST
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I have 500-600 rounds through my MCR now, and when fed from a belt it still has a failure to feed about 5-10% of the time where the round is only partially stripped from the link and fed halfway in the chamber. I've tried turning the gas valve up to three dots, and I've tried using an MG34 recoil spring cut down to 30 coils. Neither did much to help. It works 100% when fed from a magazine. I have a DTT FRT in the gun and FRT mode the ROF is noticeably higher when mag-fed vs. belt-fed. I assume this is normal(?) Do I just need to break in the MCR more, or is there anything else I should try? |
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TN, USA
Joined:
Jun 2021
Posts:
1006
EE: 0% (0)
TN, USA
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Originally Posted By Type7SOT: That doesnt work. The carrier key and/or feed stud will crash into the lower. Originally Posted By Type7SOT: Originally Posted By H1-HUMMER: stretch your links edit: I also use a vltor A5 buffer tube/std buffer, you get another 1" of travel That doesnt work. The carrier key and/or feed stud will crash into the lower. I might have said that wrong, I’m using the A5 with a shim in the back of the buffer tube, and making dam sure the lug doesn't make contact with lower, it’s a gen 5 shrike with a m16 lower |
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Originally Posted By H1-HUMMER: I might have said that wrong, I’m using the A5 with a shim in the back of the buffer tube, and making dam sure the lug doesn't make contact with lower, it’s a gen 5 shrike with a m16 lower But you are using a standard length buffer? If so, the shim must be about 3/4" long otherwise it would definitely be hitting the lower. Sorry, not trying to be argumentative, just trying to understand. I designed a whole new upper which accomplishes exactly what you are describing (either a short buffer in a standard tube, or a standard buffer in an A5 tube) so your post piqued my curiousity. |
Joined:
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Posts:
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TN, USA
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Originally Posted By Type7SOT: But you are using a standard length buffer? If so, the shim must be about 3/4" long otherwise it would definitely be hitting the lower. Sorry, not trying to be argumentative, just trying to understand. I designed a whole new upper which accomplishes exactly what you are describing (either a short buffer in a standard tube, or a standard buffer in an A5 tube) so your post piqued my curiousity. Originally Posted By Type7SOT: Originally Posted By H1-HUMMER: I might have said that wrong, I’m using the A5 with a shim in the back of the buffer tube, and making dam sure the lug doesn't make contact with lower, it’s a gen 5 shrike with a m16 lower But you are using a standard length buffer? If so, the shim must be about 3/4" long otherwise it would definitely be hitting the lower. Sorry, not trying to be argumentative, just trying to understand. I designed a whole new upper which accomplishes exactly what you are describing (either a short buffer in a standard tube, or a standard buffer in an A5 tube) so your post piqued my curiousity. no worries I experienced the same stuff OP is having, streaching links helped, lubing ammo/links helped, tumbled links didn't help, V5 helped, been on fence on buying a feed guide (link at bottom) bought this like 10+yrs ago, works great in my 16 with different length uppers https://www.vltor.com/shop/ar/receiver-extensions/re-a5-vltor-a5-buffer-tube-kit/ https://www.vltor.com/shop/ar/buffer-components/vltor-a5-buffers-2/ https://www.sturmgewehr.com/forums/index.php?/topic/27576-wts-shrike-mcr-feed-guide-insert/#comment-108545 https://www.ar15.com/forums/Armory/New-Fightlite-MCR-upper-4000-Raptor-/65-554887/ 
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Originally Posted By H1-HUMMER: I might have said that wrong, I’m using the A5 with a shim in the back of the buffer tube, and making dam sure the lug doesn't make contact with lower, it’s a gen 5 shrike with a m16 lower Originally Posted By H1-HUMMER: Originally Posted By Type7SOT: Originally Posted By H1-HUMMER: stretch your links edit: I also use a vltor A5 buffer tube/std buffer, you get another 1" of travel That doesnt work. The carrier key and/or feed stud will crash into the lower. I might have said that wrong, I’m using the A5 with a shim in the back of the buffer tube, and making dam sure the lug doesn't make contact with lower, it’s a gen 5 shrike with a m16 lower If you're using an A5, with a shim at the bottom, what exactly are you accomplishing? A longer spring? |
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I also have two lowers and both use a FCD A5 length buffer tube. They both have spikes H3 tungsten powder buffers and run no spacers. I run one with a FRT and one with a super safety. There’s zero damage to lower and BCG doesn’t hit the lower or tube threads. It has the provided factory recoil spring. I have only experienced your issue when using 55gr 223 PMC bronze and never have that issue with 62gr. I did try using a hydraulic buffer from kynshot and had issues where it wouldn’t strip a round and rides over the brass. I’ve never stretched links and use brand new battle labs M27 links. I do run suppressed with a saker 7.62 or a surefire SOCOM gen 1 suppressor only though. I also break in the uppers wet at first for about 500-600rds. Like I have a spray bottle with regular car oil and spray the feed tray area and links/ammo during that time. Makes a little mess but both my Fightlite both MCR and Raptor ran like sewing machines after and even get away with 55gr 556 now suppressed. You can play with buffer spacers but with the FCD A5 and spikes H3 tungsten I have no issues with either FRT or super safety. |
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Sounds like tight links. Generously use LSA on all your upper I internals and call your links. See if it helps. LSA for sale |
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What’s your buffer setup? Length of tube, buffer, spring, and if you’re using spacers or not. I highly doubt you need to stretch your links. I’ve never stretched links in my life and have maybe a single round stoppage once in awhile and I just manually clear it by racking the BCG and back in business. It just. Really doesn’t need to be done for M27 links in modern times. It’s more of a saying and thing of the past. Your issue is likely the fact you’re shooting 55gr or weak M193 from a place claiming to be M193, regardless the system was intended for 62gr M855, but you can get it to work with 55gr. I’d try shooting a belt if 62gr 5.56 and seeing if you still have the issue. Or You might be using a H1 buffer or a carbine buffer tube and spacers. |
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Originally Posted By har1340: I thought the break in stated 500 rnds of M855? It does 100% and it also states it’s designed to run M855 or 62gr 556 exclusively. You can usually get them to run on 55gr 556 suppressed once they’re broken in. But there’s also some things you can do to kinda speed up break in and run more efficiently during the process. |
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Redman, When running a super safety do you have problems with it changing from super to safe or semi when firing? Tried one out this weekend with my MCR and I had to put my finger on each side to hold it in the middle position because it would move left or right when firing. |
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Originally Posted By hawkin: Redman, When running a super safety do you have problems with it changing from super to safe or semi when firing? Tried one out this weekend with my MCR and I had to put my finger on each side to hold it in the middle position because it would move left or right when firing. Did you have a safety detent in it? You are supposed to round over the tip of the safety detent so that it isn't so pointy.. but maybe the gun you were using didn't have one installed? Or maybe the detent was ground totally flat? |
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Originally Posted By SGT-Fish: Did you have a safety detent in it? You are supposed to round over the tip of the safety detent so that it isn't so pointy.. but maybe the gun you were using didn't have one installed? Or maybe the detent was ground totally flat? The detent was in and worked fine on a different upper. I'll try a different detent next time and see if that helps. |
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Originally Posted By hawkin: Redman, When running a super safety do you have problems with it changing from super to safe or semi when firing? Tried one out this weekend with my MCR and I had to put my finger on each side to hold it in the middle position because it would move left or right when firing. Negative. I do find sometimes I bump into it if I get up and move and get prone again if I’m doing drills with it which I don’t do often because it’s expensive, but nope. Stays in semi or full semi all the time. I do run my FRT lower more since that one has a modified bolt release on it that’s a phase 5 type drop in. It’s a huge game changer to have on any lower you run with the MCR since you can lock bolt and release bolt with your trigger finger. If the detect is pointy it should even move left to right. It might have been ground to much, or the safety barrel was not cut properly. Have you tried dumping a mag on a regular upper? Does it do it after X amount of rounds or only in certain situations? How hard is it to push left to right? There should be a pretty decent amount of force, I’d say definitely more than a 10/22, and a tad more than the force required on a Benelli M2 if you have either of those to compare against. If you do have a spare decent I’d recommend putting sand paper on desk and making a small few inch pass with light pressure and putting back in and trying until it’s got good resistance and re-try shooting it. It’d take a min to get setup but worth it to tune it to your exact preference. |
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I have an early Shrike. I have the 12.5" shorty barrel and a 16" barrel. Both with the 3 position gas regulators. The 16" works even on low gas with 55Gr. The 12.5" I never got to work on low or med. Unless using a can and I don't like burning up cans for no real good reason. That said, the 12.5" even on high gas would have FTF's until I added a cheap Bulgarian gas 'booster'. I think these are great if you don't want to shoot suppressed and just need a bit more backpressure. Below are some old videos of mine with the booster and the 12.5"  Osprey21 running my Shrike  Shrike 100rnd beltpull Now many thousands of rounds later, the 12.5 runs without the need for the booster. |
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Originally Posted By amphibian: I have an early Shrike. I have the 12.5" shorty barrel and a 16" barrel. Both with the 3 position gas regulators. The 16" works even on low gas with 55Gr. The 12.5" I never got to work on low or med. Unless using a can and I don't like burning up cans for no real good reason. That said, the 12.5" even on high gas would have FTF's until I added a cheap Bulgarian gas 'booster'. I think these are great if you don't want to shoot suppressed and just need a bit more backpressure. Below are some old videos of mine with the booster and the 12.5"  https://www.youtube.com/watch?v=x7irDkGwVxg https://www.youtube.com/watch?v=ariKRBawH1ANow many thousands of rounds later, the 12.5 runs without the need for the booster. I very rarely ever run un suppressed especially on the 12.5” but I did consider trying to have the gas port opened up. Did you ever consider that by chance? Or ever have some of the piston material removed? I’ve contemplated it but haven’t wanted to ruin such an expensive barrel. My thought is it could work, but I’d only do it have the ability to shoot 55gr or un suppresed reliably. What gas booster in particular did you purchase? |
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Originally Posted By redman797: I very rarely ever run un suppressed especially on the 12.5" but I did consider trying to have the gas port opened up. Did you ever consider that by chance? Or ever have some of the piston material removed? I've contemplated it but haven't wanted to ruin such an expensive barrel. My thought is it could work, but I'd only do it have the ability to shoot 55gr or un suppresed reliably. What gas booster in particular did you purchase? I use Bulgarian AK74 booster which are threaded 24x1.5mm and I have an adapter to convert to 1/2-28.  |
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