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A Tale of Two Crush Washers, or Two Crush Washers One Barrel, and other AR oddities
- Thread starter cmshoot
- Start date
Not gonna buff out though.
Kaboom in a 6.5CM with handloads. My best guess is the right charge of the wrong powder…….or the wrong charge of the right powder.
Other than the brass pasted to the chamber, and the barrel extension, the barrel seems to be in perfect shape. Nothing in the bore, and no bulges.
Other than the brass pasted to the chamber, and the barrel extension, the barrel seems to be in perfect shape. Nothing in the bore, and no bulges.
Is the extractor damaged too?
Factory S&W M&P-15, brand new and never fired. Brought in by a customer. The plan was to cut down the railed gas block to fit under the new BCM MCMR KMOD rail.
Customer left the upper with me so that I could cut and shape the gas block, having it done later in the week. After the gas block work, then I would re-assemble the upper with the new BCM rail.
Shortly after the customer left, I pulled the upper receiver apart. A little hard to tell in the pic, but the lands on the threads are silver where the anodizing is worn/cut through. Never seen that on a brand new assembled upper before.
Put the barrel back in the upper, and slid it onto the Midwest Industries URR so that I could install and torque the new barrel nut. The barrel extension did not want to seat onto the URR easily, which told me that the upper receiver and the barrel extension were no in proper alignment.
Pulled the assembly back off the URR, and saw that the feed ramps were not aligned properly. At this point, I wasn’t sure if the issue was with the barrel, or with the upper receiver.
Tried 3 others barrels on the upper, and all aligned perfectly. This meant the issue was with the factory barrel.
Called the customer, and went over some options with him. We decided to replace the barrel, so that the finished build could benefit from a midlength gas system. Replaced the barrel with a Ballistic Advantage 16”, nitrided, midlength gas sytem, NiB barrel extension, and factory-pinned gas block. A very nice barrel for $200, especially when you consider that it comes with a pinned gas block.
Upside was that once we decided what to do, I had the upper assembled with the new barrel and rail in 20 minutes. Customer came back and picked it up. While I had the rest of it, I disassembled the BCG, dumped the donut, properly lubed it inside and out, and put it all back together for him.
I advised the customer to contact S&W about the misaligned barrel extension and see if they are willing to do anything for him.
I love it when a plan comes together.
Customer left the upper with me so that I could cut and shape the gas block, having it done later in the week. After the gas block work, then I would re-assemble the upper with the new BCM rail.
Shortly after the customer left, I pulled the upper receiver apart. A little hard to tell in the pic, but the lands on the threads are silver where the anodizing is worn/cut through. Never seen that on a brand new assembled upper before.
Put the barrel back in the upper, and slid it onto the Midwest Industries URR so that I could install and torque the new barrel nut. The barrel extension did not want to seat onto the URR easily, which told me that the upper receiver and the barrel extension were no in proper alignment.
Pulled the assembly back off the URR, and saw that the feed ramps were not aligned properly. At this point, I wasn’t sure if the issue was with the barrel, or with the upper receiver.
Tried 3 others barrels on the upper, and all aligned perfectly. This meant the issue was with the factory barrel.
Called the customer, and went over some options with him. We decided to replace the barrel, so that the finished build could benefit from a midlength gas system. Replaced the barrel with a Ballistic Advantage 16”, nitrided, midlength gas sytem, NiB barrel extension, and factory-pinned gas block. A very nice barrel for $200, especially when you consider that it comes with a pinned gas block.
Upside was that once we decided what to do, I had the upper assembled with the new barrel and rail in 20 minutes. Customer came back and picked it up. While I had the rest of it, I disassembled the BCG, dumped the donut, properly lubed it inside and out, and put it all back together for him.
I advised the customer to contact S&W about the misaligned barrel extension and see if they are willing to do anything for him.
I love it when a plan comes together.
I’ve seen more issues with AR’s and AR parts in the past year than in the previous 10. This covers all price point from the cheapest to some of the top tier stuff, although the cheaper the stuff the more issues I’ve seen.
Some of the issues that I’ve seen on complete guns are issues that you should be able to pick up on a good, visual inspection.
-fixed front sights that are obviously canted (fix is a new barrel)
-ejection port cover that won’t stay closed because the holes for the hinge pin are located wrong (fix is a new upper)
-misaligned feed ramps
Issues on parts:
-gas tubes with no gas port, or the gas port on the top of the tube instead of the bottom
-BCG’s with poor, or no, staking on the gas key
-castle nuts and other parts that aren’t threaded
-ejection port hinge pins that are too long, which can interfere with the barrel nut and/or rail
Some of the issues that I’ve seen on complete guns are issues that you should be able to pick up on a good, visual inspection.
-fixed front sights that are obviously canted (fix is a new barrel)
-ejection port cover that won’t stay closed because the holes for the hinge pin are located wrong (fix is a new upper)
-misaligned feed ramps
Issues on parts:
-gas tubes with no gas port, or the gas port on the top of the tube instead of the bottom
-BCG’s with poor, or no, staking on the gas key
-castle nuts and other parts that aren’t threaded
-ejection port hinge pins that are too long, which can interfere with the barrel nut and/or rail
The instructions I got from CMMG was to shoot a 223/556 round through it after swapping the bolt back in order to BLOW OUT any carbon. That's seems to work well as I've never had any issues over the years.
