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Posted: 3/9/2014 12:34:48 PM EDT
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Back in late 2007 I was bit by the retro bug and built a 601 replica. Got a Colt smoothside upper off GB, a Nodak NDS-601 lower, a complete CMMG 20" pencil barrel assembly including delta ring, FSB,and gas tube. Found some furniture and painted it with some green paint from a member of this board. Shot it a few times and noted it didn't cycle well, especially with Wolf ammo. Win.,Rem., and Prvi seemed to work better. Then the recession hit, and I put my toys away for a while. Now I'm getting back into the game. I have maybe 100-200 rounds through this rifle at this time. Got the 601 out the other day to put it through its paces. Found 95% of the time it will not cycle Wolf ammo. Fires, ejects empty, resets hammer but does not feed a new cartridge into the chamber. You pull the trigger, CLICK. Bolt does not lock back after the last round. Cartridges feed fine using the charging handle. Basically I have a straight-pull manual feed rifle. I have been reading the old posts here. Pulled the BCG and removed the bolt. Carrier slides fine in the upper, no binding. Pressure tested the carrier and gas key, no leaks. Pressure tested the gas tube and block, found a lot of leakage where the tube goes into the gas block/FSB. Found the gas tube retaining pin came out easily, and the gas tube pulled out without much resistance. Measured the gas tube OD, .180. Checked the hole in the front sight base for the gas tube. Using my number drill bit set, a #13 bit measuring .184 goes in about 1/2" (far enough to reach the gas port and beyond). The hole narrows down to about .182 from that point in. There is a lot of scorching/powder fouling on the gas tube around the gas port, indicating a substantial leak.
Am I correct that this is my problem? What options do I have to fix this? Do I have to replace the front sight base? If this is the case,is CMMG likely to warraranty this problem given the amount of time that has passed since I bought it? |
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You could use something like Blue loctite to mount the gas tube to seal off the leak between it and the gas block if you can not get it warrantied, but will make pulling the tube at a later date a major PITA (read will need to heat up the tube to break the loctite bond).
Also to note, it may just take some chamber break in with live fire before the barrel will run coated ammo. If the gun runs fine with brass case ammo, then would dare to guess its a combo of clean and lubing, and chamber break in/self polishing through live fire that may solve the problem instead. To add, since you are shooting coated ammo in the rifle, make sure that you are using a chamber brush with CLP to scrub the hell out of the chamber to remove the powderized poly fouling that get scrapped off the ammo and collects in the chamber. Normal cleaning products will not dissolve the polyurethane fouling that is scrapped off the cases and collects in the chamber, and it has to be scrubbed out instead. |
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Thank you for your replies.
I had thought about a different gas tube. Measured a spare tube I had on hand and one on another rifle that functions OK. All three measured the same. If I could find one slightly "out of spec" ( slightly larger in diameter) I'd like to try it. Worth a shot, anyhow. I thoroughly cleaned the chamber and even polished it with automotive polishing compound on a rag wrapped around a .30-cal brush hoping there were some deposits or reamer marks left in the chamber. No improvement. |
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