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Stripped Round Will not go into Battery


warthog984

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I think its a mag problemo.....check your mag release....is the stud almost even with the mag button? does the mag drop freely?

put a round in a mag with bolt back in the catch.....look inside thru the ejection port and see how the round looks/angle in relationship to the ramps.....mag has to be high enough so the round looks like it will slide right into chamber....seen this before......you may have to tweak the mag lips to get proper angle/height

also your mag spring/follower...could be hanging up....take a lil oil and a dowel push down a few times

on the mag........the mag aint positioned right in the magwell is is my 2 cents :) Wash

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 He's using PMag's , so I wouldn't recommend any feed lip manipulation  <laughs>

   I'm still looking for my measurements showing the feed height from the deck of the lower receiver , I have them & photo's some where . I did see that at one point I pre-loaded the PMags the day before a range trip & they seemed to work with them fully loaded over night , but found that after that they FTF .

   If I remember correctly (I need to find the measurements I took ), that the was a 0.011" difference on how high the PMag & DPMS mag's seated in the CMMG Lower receiver. The Pmags sat lower, when measured from the flat deck of the lower to the top surface of the base of a loaded cartridge case when loaded in the inserted mag... 

   I can take the measurements again , if I don't find them . I looked a little for that thread I made on this subject, to no avail . Will keep looking .

 

   Its all about the process of elimination , the  different Magazine manufacturer try is easy & inexpensive. Could we have some photo's of your feed ramps ?

 

  Since you feel so highly of my recommendations , I recommend you all give me your 308AR's for my pleasure . >:D

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Wart   here's mine one is a pmag one is a dpms mag      blurred one is pmag...cellphone photog no bueno...looks like you are low to the chamber?

  :)  Wash      clean that nasty chamber   lol

 

20140804_121941_zpse5xcrtg8.jpg

 

 

20140804_121911_zpsutnfd8dn.jpg

Edited by washguy
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Thanks Wash.....I cant really tell much from your pictures.  If it is only of a .001, I cant tell with these non-calibrated eyes.  The chamber is dirty as hell from all the lube. I have hand cycled this actions way to many times.  The bolt carrier does move smooth now.   ::)    Note that I did clean the chamber before test firing it.

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   Its hard to tell comparing the different rifle feed ramps , but Washguy' cartridge , when on the left of the mag. looks higher up . Could be just the angle of the photo's .

 

   Have you loaded one round & fire it , does it hold back with the bolt stop on the empty mag.. When you insert a empty mag in the rifle & pull the charging handle all the way back , does the bolt catch engage & hold the BCG  back ?

   If the Bolt carrier is striping the round out the mag. instead of the bolt , this will also cause FTF. 

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Wtf bro? That's not failure to feed! Your bullet fed fine. That looks like a failure to go into battery. You need to double, triple, quadruple check that you are using the correct buffer and spring.

A failure to feed would have the cartridge jammed up in the receiver. Never making it into the chamber/barrel.

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The initial title for this issue was failure to go into battery.  I just piggy backed on what survivalshop said in post #38.  I have a Magpul UBR stock with DPMS 308 carbine buffer spring and DPMS carbine buffer.  As far as I know, that is the correct stuff.  Magpul UBR uses AR15 carbine length tube.  Can someone give me carbine spring and buffer measurements?   I can measure to make sure i was sent the right stuff.  The package says 308 carbine.  The bolt hold open works.  I would figure if the buffer and spring were wrong, the bolt hold open would not function on an empty mag.

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   That's why photos are so important  & that's why I asked for some , I don't like the looks of your chambered brass , but new barrel , who knows   

 

 

You say this barrel head spaced correctly, with the correct & known good gage & which gages did the bolt lock into battery with  ?  

 

     Will a full 308 cartridge hand ( just your hand , no BCG ) feed into the chamber with out forcing it in ( you can separate the upper from the rifle ) ? I use dummy hand loads for this or use a dummy cartridge  <thumbsup>

 

     The round will feed up the ramp , but fail to completely chamber  & lock into battery for firing , is this correct ?

 

      Are the ejector & extractor , in your bolt free to move & not sticking ?

 

 

  I'm just trying to get on the right track here , no offense .

 

 And to think I just found the mag height measurements I was looking for & don't think they are needed now. you have other problems.   <laughs> I will post them any way , let all of you figure it out .

 

 

  Measurements were taken with a fully loaded magazine ( 20rds in The PMag & 19 in the DPMS ) I measured from the flat ledge or deck of the lower receiver to the upper top of the cartridge case base( I will take a photo if you are not sure how I'm measuring ) .

  One measurement was with the magazine brand in a DPMS lower Receiver & another in a CMMG lower that has had problems feeding with one manufacturers magazine .

 

 

LR/PMag                 CMMG Lower           0.396"

 

CProd.                      CMMG lower            0.405"

 

 DPMS                      CMMG lower             0.403 "

 

 

LR/PMag                    DPMS lower             0.422"

 

 CProd.                        DPMS lower             0.454"

 

 DPMS                          DPMS lower            0.456 "

 

As you can see the lowers have the magazine at different heights . May not seem like much , but it kept one of the magazines from working properly, since it was only the one manufacturers magazine that didn't work , it shows you it doesn't take much to get out of spec's to cause failures .

 

   I do not in any way blame the Manufacturers , CMMG was made years before the LR/PMag .

Edited by survivalshop
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My thoughts......

 

I'm looking at the pics and I think the rounds are being dented or ever so slightly bent while being fed from the ramps. This is likely because the mags are sitting too low (tolerance stacking perhaps) and the rounds are going in at an extreme angle as they feed in/up the ramps. With the bolt slamming at the rear of the cartridge at speed, I'm not surprised that this is happening.

 

I assume they chamber in nicely if you ride the charging handle all the way home, right? How about using an empty mag, and load one round in from the ejection port, and ride it home......

 

The "bent" cartridges are getting jammed into the chamber causing marks consistent with what you're getting.

 

....so I went to measure my CMMG lower at the front "cut" edge since it's a clearly defined line.... (8.47mm = .333")

 

IMG_20140804_182622.jpg

 

...and took some feeding pics so you have something to compare against....

 

IMG_20140804_182930.jpg

 

IMG_20140804_183000.jpg

 

IMG_20140804_183045.jpg

 

OK... off to clean my dirty rifle. :D

Edited by shibiwan
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Wtf bro? That's not failure to feed! Your bullet fed fine.

 

 

Yep, I'm seeing something similar from that last batch of pics (EDIT - from that last batch of pics prior to, and right above, Rob's post that I quoted) - I'm seeing the centerline of the cartridge that's ABOVE the centerline of that bolt.  That's a machining issue.  A pretty big machining issue.

 

 

 

If that's what it really is...

Edited by 98Z5V
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This is going to sound really silly... I'm assuming that you haven't shot this rifle yet... are you sure that's a .308 barrel?

 

 

 

I was also wondering this - from the marks on the brass, and only SO far on the brass, it looks like a 308 Win bullet was jammed about as far in as it can possibly go...  into a 300BLK barrel.

 

 

Cartridge base won't even seat into the bolt face - looks like trying to jam a 308 Win cartridge into a 5.56 bolt...

 

 

 

 

post-7-0-86513000-1407221310_thumb.jpg

post-7-0-25267100-1407221313_thumb.jpg

post-7-0-78311800-1407221314_thumb.jpg

post-7-0-66037000-1407221317_thumb.jpg

Edited by 98Z5V
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Second look at the carrier - that's not a 5.56 carrier... 

 

 

 

Very concerning...  But not a 5.56 BCG...

 

M4-looking feedramps don't look right - in a 308.  Something not right going on.  Upper ramps are one angle, barrel ramps are another...

 

Lots going on here, but WTF is going on here...  <dontknow>

 

EDIT - just re-read all the initial stuff - chambers by hand.  Bolt locks into place, all the way forward?  Fully seated bolt? 

 

Out of ideas at this point...

Edited by 98Z5V
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