cycling/ejection problem

[Aznative]

Hello and I'm glad I found this site.  I'm having extraction problems on a custom built Armalite AR-10B chambered in 243 winchester.  I purchased the parts for this build right about the same time DPMS and others started building 308 ARs. At that time Armalite dominated the market.  I estimate this rifle has 500-700 rounds through it and it started throwing the fired case partially  out and the bullet being feed from the magazine would get jammed and even bent in the barrel extension.  I have a picture of a round where the case flipped 180 degrees and lodged between the bolt face and the extraction  port with a bolt from a different AR10  I purchased both a go and a nogo headspace gauge before swapping the bolts and it still jammed using factory ammunition instead of my usual reloads.  I just purchased from Armalite an adjustable gas block, an extractor kit, and new gas rings.  FYI: I fired the gun with one in the chamber and an empty magazine and the magazine held the bolt open.  I purchased the gas block because I'm not sure if the gun smith reamed the gas port to the proper spec for this caliber.  I compared against a functioning AR-10  the gas tube for proper extension into the breech area and the bolt carrier key for being straight and tight.     

I have a question:  In the extractor kit there is a very small plastic rod that isn't even listed with a part number but shows up in the picture at Armalite's web site and was included in my kit. .  What is the plastic rod used for?   The only thing I can think of is maybe an alignment dowel used just during assembly.  

Here is a link to Armalite's picture of the extractor kit: https://armalite.com/shop/ar-10-extractor-replacement-kit/

Thanks to all respondents.

[Aznative]

I went ahead and put the bolt back together with the new ejector, ejector pin, ejector spring and the oring.  I also installed a new McFarland gas ring.  The ejector spring may be the part of the problem.  It is considerably shorter than the new one, but that doesn't explain why I had issues with another bolt assembly from and know working rifle.  I was going to wait but I decided to put the adjustable gas block on the rifle too.  

http://s1186.photobucket.com/user/Arznative/slideshow/AR10

 

Edited January 30, 2016 by Aznative

[unforgiven]

Someone with more smarts than me will come along brother,never have seem a case spun 180* before.Strange $hit.

[survivalshop]

    Ejector or Extractor , I assume because of the kit in the link , its an Extractor kit . That may be all it is , but it could also be the Ejector or both , try the Kit you have & you will know . Check your Gas Block also .

 Issue with the foreign Bolt could be just that , I have a Barrel/Extension that will work with two Bolts , but not with the Bolt I got for it . That Bolt works in both my other 308AR's , go figure , they all Head Space fine .

[Aznative]

I took a punch and pushed down on on the ejector plunger on both a working bolt and the problematic bolt.   Not an accurate way to check the ejector spring but better than nothing.  If it still jams,  I'll have to buy the ejector kit and measure the roll pin before buying the drift punch.  I have a lot of punches and chisels but nothing smaller than 1/8th inch.  

One of the first things I did was  I sprayed carb cleaner with the straw attached to the nozzle down the gas tube while watching down the barrel.  The port  flowed carb cleaner well and I also blew it  out with  along tipped blow gun through the bolt carrier bore with at least 120 psi compressed air after letting the carb cleaner soak a few minutes.  Come to think of it I have some GM top end engine cleaner that I could have used.  This stuff is designed to clean carbon off parts.  

 

Thanks for the help

[Aznative]

I took the AR10 out to some nearby National Forest land to test fire it.  I started by getting the adjustable gas block set.  I started with the adjusting screw one full turn out and firing one chambered round with an empty magazine to see if the magazine bolt catch would work.  I then opened it up 1/4 turn at a time and repeated the magazine catch test.  It finally held the bolt open after it was opened 2 full turns.  The cases were landing at 4:00 looking while looking down the barrel at this point.  I opened it up another 1/2 turn to get it to land the brass at three o'clock as per this tech note:

I then proceeded to run another 25 rounds through the gun with zero hiccups.  Since this problem started, it would start jamming at least within five rounds and usually after three rounds so I'm declaring the rifle fixed.  I usually shoot a different load but it should run just fine.  It is basically the same load except I simply substituted 88 grain varmint Bergers with 87 grain Hornandy VMAXs because of price and quantity on hand.

Everyone Thanks For the Help

 

[survivalshop]

   That's great . Springs do wear out , as do other components in the Bolt , I keep spares.  

[beantown]

   That's great . Springs do wear out , as do other components in the Bolt , I keep spares.  

Spare parts and springs are next on my list.

[Rsquared]

Good deal Az.

[Sisco]

Glad you got it fixed. Az. Thankful I scored those two spare parts kits off mraley a while back, never know when you are going to need them.