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Posted: 11/23/2007 1:47:57 PM EDT
Okay gang here goes.
I just got done machining a 0% lower receiver from DSArms. I had a 6.8spc upper that I got off of the EE to go on it. We were doing some proving runs today and ran into a couple of issues. I need some help.

One: FTE - Opon ejection, not all rounds were ejecting fully. The ones that were hanging up were caught in between the Bolt carrier and the lugs of the barrel extension. Base of the case facing towards the rear of the rifle as in the proper position.

Two: After firing, the next round would not feed.

Three: AND HERE IS THE WHOPPER! While working the first two issues, the weapon fired, and now the bolt is locked into battery. It won't budge...not an inch. The charging handle won't move the bolt carrier at all. It is locked in there solid as a rock. I have no idea how to get the bolt unstuck. Any help would be great. Thanks in advance!

Dan
Link Posted: 11/23/2007 2:35:16 PM EDT
Not sure about your first two issues, but for the bolt being stuck, try slamming the buttstock on the ground while pulling on the chargins handle. That will usually open things up.
Link Posted: 11/23/2007 9:42:13 PM EDT
Link Posted: 11/24/2007 8:33:03 AM EDT
First I would like to thank you all for your fast posts. I had the upper off the lower, so I went with a brass drift and gave the carrier a solid whack. Out popped the bolt much to my surprise. I have the casing and will post pictures. There is a bolt lug pinch on the rim of the case. I will try and get a picture posted. Maybe you all can give me a clue as to why the bolt locked up on the case rim. Other than that, I now need to find out why the thing seems to be short stroking. I was shooting reloads, but of three different work-ups. I think on the mediums and hots, the ejection was fine. I believe that the lights are what the gun did not like. Now that I have the bolt unlocked and the gun back together, I will have to run some more tests. Again, thanks a bunch for the posts. I will try to get some photos of my 0% lower that I machined posted in the "show off your stuff" forum.

Dan
Link Posted: 11/24/2007 9:19:08 AM EDT
Just for the hell of it, you're not shooting 5.56 in a .223 chamber are ya? That could cause some problems.
Link Posted: 11/24/2007 12:42:58 PM EDT
[Last Edit: 11/24/2007 1:31:31 PM EDT by FileForge]
JohnQ...nope, it is a 6.8spc

Here is a couple pictures of the lug pinch on the case. Hope someone can explain why this happened.

http://farm3.static.flickr.com/2410/2060861974_2ce68bbe4a.jpg?v=0

http://farm3.static.flickr.com/2210/2060080783_2e53cf0dbd.jpg?v=0

Link Posted: 11/24/2007 1:04:46 PM EDT
My brain fart, missed the 6.8 in the original post. Pics are not working.
Link Posted: 11/24/2007 3:29:28 PM EDT
That pic looks more like the extractor ripping the case rim upon extraction, bolt movement. It would seem to me that your bolt/carrier is starting to move too early in the cycle, when chamber/barrel pressures are too high to pull the case from the chamber cleanly. I would highly recommend you read this thread, as it will explain how everything works in conjunction with each other.

http://www.ar15.com/forums/topic.html?b=3&f=66&t=266108

By the way, nice rig, but I would highly recommend getting it anodized. Here is a pic of mine build from a 80% unit tha tI finished up on a drill press then took to professional anodizer. Just remember, the anodizing will make your holes smaller by about .001" in diameter.



Link Posted: 11/24/2007 3:40:28 PM EDT
JohnQ

I just finished it over the last 36 hours or so. When finished, The lower will be the same color and finish as the upper. I am shooting Lauer Duracoat in my paint booth.

I will read the thread that you recommended. Thanks for the input.

Dan
Link Posted: 11/24/2007 4:19:36 PM EDT
No problem. However, the anodizing is not just for appearance or color. It actually hardens the surface of the aluminum to help protect against wear. With the spring tension on that hammer pin, and the constant movement of same, I would not recommend using it too much without anodizing. The pin I would think would wear the bare aluminum rather quickly, but I'm not so sure about the Duracoat. Course that's just my opinion, which ain't worth much I guess. But let us know how it holds up.
Link Posted: 11/24/2007 11:13:01 PM EDT
[Last Edit: 11/24/2007 11:17:47 PM EDT by mjcarter]
The primer appears to have soot around it. Too much residual chamber pressure causes the cartridge case to grip the chamber wall upon attemped extraction. Maybe too large a gas port hole or too short a barrel? Maybe a rough chamber? Just guessing.
Link Posted: 11/24/2007 11:13:32 PM EDT
[Last Edit: 11/25/2007 2:10:37 PM EDT by Dano523]
Link Posted: 11/25/2007 5:16:31 AM EDT
Well, thanks for all the input guys, but let me throw another loop at you. From the first post on this thread, I mentioned that the bolt had locked into battery. I had to disassembly the upper from the lower, and then use a brass drift to whack the rear of the bolt carrier to get it unlocked. When the bolt popped free, the case was not with it. We had to remove the case from the chamber as it was still in there after we removed the bolt. SO, my question now is, could the extractor tear on the rim be from when we forceably removed the bolt from the case during the whacking rearward of the carrier. I wonder if I had a case that didn't size correctly and was stuck thus locking up the bolt. When we whacked the bolt backward, with the case still stuck in the chamber, the extractor tearing off the rim would give the same effect yes?? I am just confused, becasue the upper was purchased used and broken in, 100 rounds or so. I figured it would just work. This is my first AR, so I am still learning. Thanks in advance for all your patience!

Dan
Link Posted: 11/25/2007 6:17:33 AM EDT
An improperly sized case can definitely cause a jam up in the chamber. Which upon forceable removal cause the case rim to be ripped off by the extractor.

Link Posted: 12/1/2007 1:29:27 PM EDT
Well, guys...I have most of the issues solved. Okay no flaming me, but it was my reloads. The cases were not fully sized and that was causing the jams up in the chamber. I am now running some factory Hornady 110s through it to work out the last issue I am having with my build...Okay here is what I have left to solve.

Using factory ammo...
Empty mag = bolt locks back on bolt catch. Stock bump on table and bolt holds open
Load one round
Fire Weapon
Case ejects, and the hammer is reset but the bolt will not latch open.

Two rounds in mag
Fire weapon
Case ejects and hammer is reset but second round will not feed, bolt is properly closed into battery.

I am assuming that this means I have a gas problem? My gas key is properly staked and secure. Rounds eject at about 3 o'clock and 3 to 5 feet. Any help would be greatly appreciated. My next step is going to be to pull the gas block and check the burn mark. If anyone can save me the trouble by all means please chime in! I sure am glad all you guys are around for us Noobs!!!

As always, thanks in advance!!
Dan
Link Posted: 12/1/2007 3:59:03 PM EDT
You're shortstroking. Yes check the gas system, and/or the gas rings on your bolt for wear or the ring gaps lining up. They are not supposed to be lined up. If ok, and you can, check the alignment of your gas block with the port in the barrel. Also, I'm not sure if the 6.8 uses the same recoil/buffer spring as does 223. That could also be your problem right there.
Link Posted: 12/1/2007 8:39:08 PM EDT
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