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Posted: 6/14/2014 4:04:18 PM EDT
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This is a fresh build for my wife, & today was it's first time out. Wont cycle right. She'll fire just fine, will eject just find, feeding is mostly fine but could be mags. We were shooting silver bear, & M855. Same issue with both types.
You'd fire a round and the rifle simply wouldn't cycle on it's own. hand cycle another round and it's the same thing. For giggles I put the buffer out of my daughters carbine in, and magically she'd cycle right. Also I tried three different bolts with both buffers, with the same results with each. Rifle buffer = no go. Carbine buffer = go. I also pulled the gas tube to check for carbon build up. good to go. Specs of the rifle: Colt 20'' government profile 1/7 barrel. Take off of a M16a2. Colt bolt, with a no name carrier. Bushmaster C7 upper. Spikes lower and Lpk Dpms a2 stock and buffer. Would it be fine to just run a carbine buffer all the time, or would that be a bad thing. Any help is greatly appreciated. 
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Carbine buffer bad. Glad it was for but a few rounds. Didn't think it was a good idea long term, or everyone would be doing it.
With the carbine buffer, the brass was ejecting at two to three o'clock. Landing three to five feet out. I'll count the coils, and measure it. Cant check the weight till Monday. Thank you |
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This is from TM 9-1005-319-23&P.
The action spring is within spec if it lands in within this tolerance. RIFLE ONLY: Free length should be 11 3/4 in. (29.85 cm) minimum to 13 1/2 in. (34.29 cm) maximum. I would use the TM above, and go through Chapter 2 to see what you can diagnose as the problem. To get you started: 2. FAILURE TO FEED Step 1. Inspect for weak or broken magazine catch spring (2). Replace magazine catch spring (WP 0021). Step 2. Inspect for defective magazine catch (1). Replace magazine catch (WP 0021 Step 3. Determine if magazine catch (1) is out of adjustment (will not retain magazine). Refer to TM 9-1005-319-10. Step 4. Check for short recoil. See Malfunction 10 |
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Quoted:
I tried different carrier groups. We took the three ar's out today, so I was just pulling the different carrier groups. Ok. From your original post, you stated bolts, not bcg's so I wanted to clarify. Still sounds like a gas issue with the rifle short stroking rather than a buffer/spring issue. Do you have a different gas tube you could try? The end that goes into the gas key might be damaged and not sealing properly since you tried different bcg's. It could also be that it's a new build (new parts?) and needs to be broken in. How much lube did you use? I'd stick with brass only for the first hundred or so rounds. |
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I think you're missing something.. 39 coils is probably a carbine spring not a rifle spring. Even with the right length, the fact it has fewer coils will make it stiffer. It probably worked with the carbine buffer because the shorter buffer doesn't compress the spring as much, there isn't a second shoulder on it. It sounds to me like it's a stretched spring.. if you've ever stretched out a pen spring you know already that a stretched spring with less coils is stiffer than one that's manufactured the correct length with more coils.
I'd start by getting the correct rifle spring with 41 to 43 coils. Worst case it doesn't fix the immediate problem but it'll make the rifle live longer and you're only out three and a half bucks anyway. There's a good chance it'll fix it though. |
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These are the springs & buffers I have at the moment
Top is a old colt spring & plastic buffer. Second down is my problem Dpms spring & buffer. Third down is a Olympic spring & buffer. Last is out of a Stag. 
These are the BCGs I tried. Top is out of a Olympic carbine. Middle is the problem child. Colt bolt with a no name carrier. Checked the gas key, & everything is lined up & clear of debris. Last is a Colt bolt & carrier. 
I didn't think to try the problem bolt in either of the other two guns. I replaced the gas tube & will get another spring this week. |
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Mattgunguy,
The first, third, and fourth "carbine" buffers and action springs are only to be used in an AR15 with a collapsible carbine stock. The second one is a "rifle" buffer and the correct buffer for a fixed rifle stock. The carrier key can be damage by slamming into the lower receiver where the lower receiver extension (buffer tube) screws into the lower if carbine buffers are used as is in a fixed rifle stock. 
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Yup. Learning the hard way. I've always been an ak guy. I'm like a walking talking ak encyclopedia, but recent eastern European issues made me rethink my dependency on foreign ammo. So I've made the switch to ar's and am still running the learning curve here. We always had a unit armorer in the army to deal with these issues, so I never really learned much there & that's been more than a few years ago now.
Thank you for all the help on this one. Hopefully I can return the favor to someone someday when I'm not so clueless myself. |
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Quoted:
Mattgunguy, The first, third, and fourth "carbine" buffers and action springs are only to be used in an AR15 with a collapsible carbine stock. The second one is a "rifle" buffer and the correct buffer for a fixed rifle stock. The carrier key can be damage by slamming into the lower receiver where the lower receiver extension (buffer tube) screws into the lower if carbine buffers are used as is in a fixed rifle stock. http://i741.photobucket.com/albums/xx54/jslegspoet/111_2973_zpsa1700691.jpg I'd be a lot more concerned about the lower than the carrier key. |
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Quoted:
Soooooo, don't screw up & accidentally use a .308 buffer spring in you 5.56 rifle. For some strange reason it'll be to stiff to cycle. Who'd of thunk it. But all is now right with it. It's the little things that'll screw things up. Congrats on getting it figured out. Sounds like you need a .308 to go with that buffer spirng! |
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