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Posted: 9/22/2002 4:06:10 PM EDT
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After a nice 16 hour work day I headed to the range to meet Campy, Waldo, Plateshooter, and Engineer to ring out my new upper equipped with a surplus Army M-261 .22lr conversion unit. The first order of business was to sight in the upper. For this I set a target at 50 yards and with the help of plateshooter dialed it in. This is a converted postban upper. 16" with 1 in 14 twist, flash hider was replaced with a pinned and welded Cav Comp. First group was about 4 inches right and 3 inches low. Dialed in on the third try. Thank you Plateshooter for always being prepared and having the proper tools for the job. Spent the next half hour hitting point of aim and averaging 1.5 to 2" groups. More than acceptable for a weapon in this arrangement. I later moved out to 100 yards shooting a 10 x 6 steel plate. 100 round fired, 100 hits, with a very satisfying pwaaaang sound that reminded me of an old western. I note that The Compensator kept muzzel rise to zero even in rapid fire, but even made the .22lr sound loud. The downside. Reliability was spotty at best. The best engineering minds in NE Ohio set out to find the cause. We concentrated on the Magazines. There was a noted fresh burr indicating the bolt was hitting the back of the mags. We switched to using USGIs as carriers as well as deburred. This seemed to solve the problem but not completely. I was still getting a couple failures every other mag. We next looked at fit, I used a cheap aftermarket chargining handle that is a bit rough, this will get the crocus cloth treatment to smooth it, as well as the inside of the upper. As it is the thing wants to run wet. We also realised that my excellent reliability from last week had been in a 20" barrel, giving the rimfire round a bit more momentum to cycle the action. We also noted that the Gas system was dumping fouling right into the action. This is a blowback operation so no gas key and vent system to expel fouling. We determined that the gas system needs to go, it was robbing energy needed to properly cycle the bolt as well as gumming up the works. The great minds got together to decide how to best accomplish this. It was first suggested to remove the Gas tube and tap the gas block and install a set screw. At once logical and simple, but irreversable in this pre to post ban conversion. What if I ever wanted to go back to .223 ??? We then decided after much discussion, that gas tubes are pretty cheap, therefore expendable. We settled on leaving the gas tube in place, but crushing it to pinch it off under the handguard. leaving the option of filling with JB weld at the receiver end. The resulting back pressure should give the action the bump it needs while keeping the fouling out of the receiver. If I ever want to go back to .223 a new gas tube is all I need. I will be making these simple mods this week. Unfortunately it will be Thursday or friday before I get to try them out. Any suggestions will be appreciated and again my thanks to Campy, Plateshooter, Waldo, and Engineer, without whom this project would not have gone as smoothly or easily. |
| Just an update. The work as described above has been completed. I chose to crush the gas tube under the gas tube under the handguard so as not to be so visible. It required using the corner of a bench vice to crush it. That is some tough tubing. I also filled the receiver end of the tube with JB weld which is setting now. This could effectively increase the pressure in the chamber allowing the unit to get enough bump to cycle effectively, while keeping the action a bit cleaner. I won't get to shoot it till Thrusday, so I'll let you know how it works out. |
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