Out shooting my relatively new cmmg mk3 and started noticing some extraction issues. Everything was fine through break in and the next hundred rounds or so. I've been shooting CBC 7.62 NATO for the brass and some of my handloads. It started as failures to eject and progressed to actual stuck casings. After the FTE I would clean barrel and chamber, it's now getting stuck casings regardless of ammo, I've tried winchester, cbc and my handloads now, eash batch of ammo, a new failure. The casings aren't showing any pressure signs, even with handloads (which I was in the process of working up, had just made it to 43grn of Varget 178grn A-Max). I'm at a loss as to what could be causing this besides a tight chamber spec. The barrel is 16" mid length gas, which I planned to change to a 20 or 24 when funds permit. Any help would be greatly appreciated as this is beginning to drive me nuts.
- Thread starter jtclarke
- Start date
Does your rifle have the extractor upgrade? The little rubber 0-ring that slips over the extractor spring really helps. So does the black insert inside the extracor spring. Most of the inserts are blue. When you install your extractor into your bolt it should take both hands to exert enough pressure on the rear of the extractor in order to insert the extractor pin
Thanks for the quick reply. It does have the O-Ring on the extractor spring, but doesn't have the insert, takes a good bit of effort to secure the extractor with the pin. I'm not having a problem with the extractor itself (at least I don't think I am), it keeps a solid grip on the casing, even to the point when the case sticks that the bolt will not travel rearward, nor can I pull the charging handle to extract. At first I thought it was a headspace issue until I tried the factory rounds with no luck.
Ejection issues are much different than extraction issues. As you said you are having ejection issues, I will only deal with that. Although the two issues are often related, I try to deal with each separately. Here is what I check first for ejection issues.
1. If the extractor has too much pressure, it pushes the casing so hard onto the inside of the bolt, that the additional pressure/friction prevents the case from making it out of the bolt in time while the rifle is cycling. Make sure that your extractor doesn't have too much pressure onto the case.
2. Check the extractor for burrs that cause the casing to hang up. Also insure that the radius on the ejector matches up with the casing's extractor rim. Manufacturing issues occasionally happen. A broken or cracked extractor can cause lotsa problems.
3. Make sure the gas system is working right. The gas key has to be tight, bolts staked properly, gas rings staggered, and not worn. Very small issues with the gas system, cause large issues in functioning. Also make sure that the gas system from the gas block rearward is working right, not leaking, or worn.
4. Check to insure that the ejector has sufficient power, and operates smoothly. If you put an empty casing into the bolt as it would appear in the chamber, then let it go, the ejector should have enough force to flip it out of the bolt sort of like you would toss a coin using your thumbnail.
5. Make sure there aren't any burrs or cracks on the bolt lugs, or the lugs on the barrel extension. These would cause the rifle to not operate smoothly.
6. If the rifle is overgassed, it works too fast for the extraction, ejection, reload cycle to happen properly.
7. Insure that the proper recoil spring is in the butt stock. If you have an carbine spring in a rifle butt stock, or the reverse, that will certainly cause problems.
8. Consider playing around with different weights of recoil buffers. Sometimes, a heavier or lighter buffer solves the problem.
These are the ejection issues I would check first. Extraction issues have a different check list, but usually extraction is pressure related.
1. If the extractor has too much pressure, it pushes the casing so hard onto the inside of the bolt, that the additional pressure/friction prevents the case from making it out of the bolt in time while the rifle is cycling. Make sure that your extractor doesn't have too much pressure onto the case.
2. Check the extractor for burrs that cause the casing to hang up. Also insure that the radius on the ejector matches up with the casing's extractor rim. Manufacturing issues occasionally happen. A broken or cracked extractor can cause lotsa problems.
3. Make sure the gas system is working right. The gas key has to be tight, bolts staked properly, gas rings staggered, and not worn. Very small issues with the gas system, cause large issues in functioning. Also make sure that the gas system from the gas block rearward is working right, not leaking, or worn.
4. Check to insure that the ejector has sufficient power, and operates smoothly. If you put an empty casing into the bolt as it would appear in the chamber, then let it go, the ejector should have enough force to flip it out of the bolt sort of like you would toss a coin using your thumbnail.
5. Make sure there aren't any burrs or cracks on the bolt lugs, or the lugs on the barrel extension. These would cause the rifle to not operate smoothly.
6. If the rifle is overgassed, it works too fast for the extraction, ejection, reload cycle to happen properly.
7. Insure that the proper recoil spring is in the butt stock. If you have an carbine spring in a rifle butt stock, or the reverse, that will certainly cause problems.
8. Consider playing around with different weights of recoil buffers. Sometimes, a heavier or lighter buffer solves the problem.
These are the ejection issues I would check first. Extraction issues have a different check list, but usually extraction is pressure related.
Thanks unknown for the response, I just now reread my OP and realize it sounds like ejecting issues, I meant extraction issues as the title of the thread says, I'm having extraction issues. Sorry about the confusion there. I did however go through the check list for ejection issues, but you let me in on some things I hadn't previously thought of and I appreciate it. The real issue I'm having is the case being stuck in the chamber after firing a round. It started as an ejection problem and moved to an extraction problem. The BCG isn't cycling (I had a friend watch the BCG when I fired a round). I first thought it could be a pressure issue, but it's failed to extract using different types, CBC 7.62 NATO, Federal GMM 168grn, and my handloads, to name a couple I've tried. After I get the cases out I'm not seeing overpressure signs either. I'm beginning to believe that the gas block could have shifted under recoil and wasn't properly secured from the factory as you said, seems that it would fit the issues, moving from FTE to the extraction issues and progressively getting worse.
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Thanks for the help guys. Turns out it was in fact the gas block. It had slid forward about a half an inch. The set screws were completely loose and had no thread locker on them. Not sure why I overlooked the simple things first and jumped to worst case.
