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Posted: 1/22/2010 4:02:32 PM EDT
i recently got all the parts in (minus the stock) to complete my first AR lower; i have a Kaiser defense KR5 stripped lower,RRA parts kit,and a Magpul Miad grip kit.but im having an unusual problem with my RRA lower parts kit.particularly the disconnecter and the hammer.once i assembled my lower and attempted a functions check i noticed two things.when i manually move the hammer back to the cocked position,it locks in place as it should,but if i continue to press it down it catches on my disconnecter....im not entirely sure if thats normal or not but its never happened on any rifle ive previously owned or used.and my safety selector doesnt rotate 90 degrees from safe to fire.more like 80 degrees but still functions.i originally thought my disconnecter spring had been improperly installed,so i checked it and all looked ok.but im still having the same problem.i contacted Rock River and explained the problems i was having and they sent out a new disconnecter and selector,but after i installed them this morning im still having the same problem.and it seems to be even worse now.any ideas? http://img638.imageshack.us/img638/1464/dsc02093.jpghttp://img190.imageshack.us/img190/2811/dsc02094g.jpghttp://img6.imageshack.us/img6/9355/dsc02102k.jpg
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| yes it is,i made sure i installed it "flared" end down when i originally put it together and then triple checked when i noticed the problem.http://img641.imageshack.us/img641/5931/dsc02107.jpg |
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So me a photo of the bottom of the receiver without the FCG parts installed,
I want to confirm that the grip screw in not protruding into the bottom of the receiver cavity void under the back of the trigger, and not allowing the trigger to return rear down far enough for a normal at rest position. |
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pictures as requested:
i removed the FCG and MIAD grip and screwed the grip screw in as absolutely far as it can go. http://img191.imageshack.us/img191/3188/dsc02172t.jpg looking into the receiver http://img706.imageshack.us/img706/1883/dsc02171z.jpg and from a better angle http://img59.imageshack.us/img59/3903/dsc02170j.jpg the shiny purple spot on the left side were the FCG would go is sharpie one of the fine gentlemen at kaiser put on to hide a blemish in the finish 
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Here you go,
http://www.ar15.com/content/manuals/lowerBlueprint.pdf Break out a caliper and start taking measurements on the lower and compare them against the prints. Best guess would be that pin holes drilled out of spec, or the depth of the void not milled deep enough if the trigger is not side binding out on the side walls causing the problem. And let me guess, even with the hammer cocked, you can not get the selector lever to move all the way to safe (back of the hammer sitting too high to allow the selector cam to clear the top of the trigger, and the same problem with the disco grabbing the hammer when the trigger is at rest. |
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Any number of things could be happening. The notch on the hammer could be slightly to long. The flat along the top of the trigger (where the long part of the disconnector sits) could be too low. The hole for the trigger pin could be drilled slightly off. The trigger and hammer pin holes in the lower receiver could be slightly off.
Do you have another AR that you could swap the FCG with? If the RRA kit works in another AR, the lower receiver could be to blame. |
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Quoted:
Do you have another AR that you could swap the FCG with? If the RRA kit works in another AR, the lower receiver could be to blame. i have two actually.a bushmaster and spikes/del-ton. ive swapped the trigger/hammer/and disconnecter in a musical chairs fashion.but ive only used my one lower.ill swap my whole FCG into the bushy see how it functions. but the reason i figured the disconnecter is the problem is because i swapped it out with another one and the hammer no longer caught,which lead me to believe i had a defective disconnecter.but when i let RRA know and they sent the knew one out i was baffled when i had the same problem. could the problem with my safety selector not rotating 90 degrees all the way to fire/safe be related?or is that a separate issue? |
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Detent track on the selector will dictate the amount that the selector can travel against the selector detent pin.
Take a look the groove in the selector edge for the two opposing dents, and do the match between those spacings for how far the selector should move against the stationary receiver detent.. |
from what ive drug up online RRA has had bad batches of safety selectors in the recent past as a result from cutting quality to meet market demand.as for the problem im having with my disconnecter/hammer im baffled.the only conclusion that i can come up with is that my parts kit is out of spec from meeting that same demand.ive put other parts into my lower to ensure its not out of spec and it functioned flawlessly.i guess the next step is to write RRA again and hope they make it right.
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I had similar problems and solved it by carefully stoneing a bit off the flat on the selector , or you could stone a bit off the top of the tail of the trigger behind the disconnector. I installled a JP trigger and believe this was mentioned in case the selector would not work.
This worked on the RR 2 stage that was too tight to the selector |
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