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Posted: 12/31/2007 7:36:33 PM EDT
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bought a cmmg 14.5'' middy about 6 months ago. my second cmmg . 1st one was flawless even with wolf. the newer one has larue 12'' handguards and a cmmg lo pro gas block. everything was peachy. then i broke my leg really bad. no shooting for 4 months. finally took it out again 2 weeks ago. again seemed like another perfect cmmg. i love them. last week i took her out and after a round fired it wouldn't strip the next off of the mag. figured out the gas block is loose as a goose and the bolt was barely going back. brought it home and tightened her up. this saturday took her back to the range to see if i did a good job. this time the bolt will not let go of the spent case and is smashing it into the chamber crushing the brass. i took the bolt out and cleaned up some debris. everything returns to normal and i do a 25 yd sight in on my irons and eotech until i have time to do it again at 100yds. tonight i cleaned her up , throw a mag in and chamber a round. i try manually cycling the bolt with the charging handle and have to pull hard as hell to extract. this is with m855. for a variable i throw a round of wolf in and pull the handle back- the round ejects with no problem . i did notice each round's primer has a light strike hit where it did not before. should i tell cmmg of all this? when the bolt slams home should it make a light strike mark? scared me a little. this is my 1st time with m855, is it usually a little snugger fit and harder to extract than wolf or winchester 223? |
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The wee little dimple is normal for 99.99% of all the AR-15's you will encounter. I suspect the Winny is a tad undersized, the Wolf, being steel does not "stick" like a nonferrous case would. That being said, I have no issues with my LC-2K M855 in my Colts, repeating your performance.. |
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Likely, no. Not enough to be so far out of whack as to pitch shots all over. If you are worried, make some witness marks with a grease pencil or marker to assure you reinstall the handguard/rail in the same position. I have one of those inexpensive LASER boresites, so I just do a quicky realign of whatever may have been disturbed in my fiddling about. Was not that much money, and saves considerable frustration at the range. |
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so i finally got to take her back out and see how my gas block fix went after loctiting. wanted check my zero too. zero wasn't far off and the gas system functioned flawlessly. but... after every 10 rounds or so the bolt will not let go of the spent casing. even if i yank back the charging handle. i had to hit the mag release and pull the round off. if not it would slam the empty into the ejection port opening or try a double feed. is this a weak ejector spring? crappy ejector. that is the only thing i can think of . i obviously cannot count on this rifle if shtf which sucks since it's my only rifle. it's like 1 thing after another. |
Did you take the bolt apart? That is, remove the extractor and inspect it? |
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Sounds like the extractor is very strong the ejector weak. You could just fire a suitable amount of rounds to wear in all the parts, given a 1 in 10 failure rate; the problem may go away. Alternatively, easiest fix is to look at the extractor and see if it's upgraded with a stronger spring, better bushing and o-ring; if so, remove the o-ring. If it's the regular extractor setup, or doing the above doesn't work, the ejector spring may be damaged, weak etc. A special device is required for removing the ejector and spring. Do you have a spare bolt you could switch and see if the problem disapears?? Most of us get a spare bolt anyway, eventually; about $45 at Bravo Company. The bolt ejector tool is about $20 through Brownells. Also: For dry cycle manipulation and testing, I simply ground the tip off of an spare firing pin. |
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sorry i took so long to get back. i went to work right after i posted. i did take apert the bolt. i dont know why i would need a special tool for the ejector. it's only a punch tool that's needed. when i got the pin out that holds the ejector, i expected it to potentially shoot across the room because of the spring tension- but it didn't move. i pulled it out and the spring and threw some clp on them. there was little specs of green from the m855 tip and specs of brass but that's it. when i looked at the extractor and it's spring they seem fine. if i get the chance i'll shoot again today and see what happens. |
Yeah, that tool does keep it from shooting across the room, or putting out your eye. Though from what you describe, you have found the problem. Cleaned out, it may work as intended. |
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Might have a slight burr inside the ejector cut out or on the ejector itself. Could also be debris. Id clean it out really well, and see if that doesnt help first. 2nd would be to replaced the ejector and spring. If that doesnt help Id get a new bolt... Light primer strikes are normal... Just dont chamber the same round over and over. AR's are not meant to cycle manually so doing so doesnt really prove anything. |
| i called cmmg and told john my problems. he apologized and said it's probably my ejector and/or ejector spring but .... he has sent me a call tag, wants to check my head spacing and the rest of my upper ,and is going to give a brand new bolt. sending it out soon. great service . |
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sent the upper back on friday. they got it on wednesday. checked the headspacing, replaced old bolt with new , test fired , cleaned and oiled. i am going away sunday and don't want my upper sitting on my porch for a week so i asked if i could upgrade the ground shipping to 2 day. 25 bucks. i got home today and the upper was there already. they charged me for 2 day but sent the upper overnight. once again- great service. cmmg is the shit. i have even more respect for them now. in addition to this carbine i have one of their lowers that a noveske upper i ordered was going on. now i am going to order a noveske lower to match so later this year i can repay cmmg with an upper to match my lower. everyone wins. |
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