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SMIC4 · February 26th, 2012, 16:42

I have a problem with a new KA (7mm bushings) m4 that's been downgraded to shoot 350 fps.

Got it from the store and test fired and everything was working fine. Including the selector, went smoothly between all firing modes.

Since I usually upgrade my own gun, I wanted to take the gun apart and compare it to my TM m4.

Take down and reassembly went smoothly, but once I got the gun back together, the selector switch got very tight when moving from safe to semi, and gets worse from semi to full auto. I took it apart to find scratch marks on the circle part of the selector switch (the part that moves the selector plate on the gear box). It seems it was rubbing against the bushing on the gear box.

When I have the gear box in the lower receiver with no body pins, or the mag release installed, the selector works smoothly. As soon as I start putting things back on, the selector starts getting tighter and tighter. It looks like all the fittings are pushing the gear box to the left causing the selector switch and the bushing to contact. I can't figure out why this is happening and I'm ready to remove the selector and just grind down the circle until it fits. What kills me is that it was fine before I opened it! Any ideas would be much appreciated.

February 26th, 2012, 16:42	#1
SMIC4 Trader rating Join Date: Feb 2012 Location: Toronto	King Arms M4 tight selector switch I have a problem with a new KA (7mm bushings) m4 that's been downgraded to shoot 350 fps. Got it from the store and test fired and everything was working fine. Including the selector, went smoothly between all firing modes. Since I usually upgrade my own gun, I wanted to take the gun apart and compare it to my TM m4. Take down and reassembly went smoothly, but once I got the gun back together, the selector switch got very tight when moving from safe to semi, and gets worse from semi to full auto. I took it apart to find scratch marks on the circle part of the selector switch (the part that moves the selector plate on the gear box). It seems it was rubbing against the bushing on the gear box. When I have the gear box in the lower receiver with no body pins, or the mag release installed, the selector works smoothly. As soon as I start putting things back on, the selector starts getting tighter and tighter. It looks like all the fittings are pushing the gear box to the left causing the selector switch and the bushing to contact. I can't figure out why this is happening and I'm ready to remove the selector and just grind down the circle until it fits. What kills me is that it was fine before I opened it! Any ideas would be much appreciated.