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Posted: 7/10/2015 11:43:42 PM EDT
[#1]
I'm going to answer part of my own question. I installed the wrong size buffer spring in my rifle. Rifle length versus carbine length. That was probably a signficant contributor to the failure to feed problem. But that doesn't answer the question of why one BCG worked while the other didn't. The only thing I can think is the older BCG has a little less friction due to wear than the new BCG, and that allowed it to overcome the extra resistance of the buffer spring. Does that make any sense or do I have another problem to look for?
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Posted: 7/11/2015 6:37:18 AM EDT
[#2]
Failure to feed is the live round not able to set tight against the bolt face.
Could be an extractor that is binding in the bolt face channel, the extractor has O ring installed with a extra tension spring that is preventing the extractor from springing open to allow the live round rim from slipping past it, the extractor is out of spec/is seated too far inward and the case rim can not spring it open as open, or the rim releif channel for the rim below the extractor claw was not milled correctly and the bottom channel of the relief channel is either too low, or too high against the bolt face. So on that note, check the extractor to make sure that it does not have a O ring around the extractor spring, hook a spent case on the extractor and cam the ejector in a few times to check to see if it's binding in the bolt face channel, then cam'g the ejector all the way in, let the spent case go to make sure that the spent case is flung off the bolt, and take a photo of the bolt face with extractor like below and post it, making sure that I can see under the extractor claw as well. 
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Posted: 7/11/2015 4:39:19 PM EDT
[#3]
I appreciate the help. Here's a picture of the end of the bolt.
Here is where the bolt sits after pulling it all the way back and locking it with the long buffer spring. 
Here is where it sits with the proper length buffer spring 
There was no O ring on the extractor spring. And here's a picture of how the extractor sits in the bolt. 
Sorry, I'm still trying to figure out how to post pictures. |
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Posted: 7/12/2015 12:47:26 AM EDT
[#4]
Rifle spring in a carbine receiver extension with a carbine buffer should coil bind the spring. The older bcg may work despite the coil bind, but coil bind is terrible for the spring. The new bcg may not travel as far to the rear as the older one due to more friction of the new gas rings, or there could be a gas leak in the newer bcg.
I bet it works fine with the correct spring. ETA: If you have a gas leak in the newer bcg, check for a loose gas key. |
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Posted: 7/12/2015 1:00:23 AM EDT
[#5]
Rock214, need one more photo of the bolt face straight on to confirm.
But what it looks like the problem is, is that the extractor is seating too far towards center line on the bolt face, and the rim of the round is not able to slide down the taper entry section on the extractor to push the extractor open to allow the case rim to seat correctly. The two top and bottom left bolts have the extractor seating correctly, and the rim of the round and a live round rim will be able to push the extractor out to allow a round to slip past to seat to the bolt face. The rest of the bolts, extractor sitting way to far inwards instead, and as the rim tries to put the extractor open, it against the flat section, instead of the taper section of the extractor instead. Ideally, you want the taper section of the extractor to line up with the bolt face recessed walls. %20face.jpg_thumbnail0.jpg)
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Posted: 7/12/2015 1:03:48 AM EDT
[#6]
KarlSG1,this has been a good learning event for me. I've built several rifles now and was getting a bit cocky about slapping them together. Nothing like trouble shooting a problem to force you to learn a lot more than you did before about what you're working with. I built another one today with a buddy and have added a lot more items to my step by step checklist.
I did check the gas key and it's tight. The rifle spring was actually trying to climb around the end of the buffer. I guess it had to go somewhere. Stupid on my part not to notice. |
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Posted: 7/12/2015 1:20:12 AM EDT
[#7]
Dano523, maybe these pictures will help...
I appreciate the help. |
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Posted: 7/12/2015 8:45:05 AM EDT
[#8]
Top of radius relieve bevel start port on the extractor should match the radius line of the bolt recess wall line.
If you look at yours will notice that the extractor is a touch more inward instead, and as the live round case when it goes to try to push the extractor open so the case rim can slip past, ends up hitting the flat section instead on the bolt face top of the extractor instead. Swap the extractors between the two B/C's you have, and see if the problem follows the extractor or not. |
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Posted: 7/12/2015 1:48:41 PM EDT
[#9]
Ok, I'll do that. If it is a bad extractor do I need a new extractor or should I try a new extractor spring first. Also, the current spring has a rubber plug inside it. Not an O ring. Is it required?
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Posted: 7/13/2015 2:43:37 AM EDT
[#10]
If you find that the extractor is defect, then get a hold of how you bought the B/C's from, and see if they will send you are replacement extractor for free to replace the defective one.
As for the extractor rubber insert inside the spring coil, that is needed. The insert keeps the spring from collapsing over time on itself. |
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