AR Sponsor
Posted: 11/1/2015 6:08:46 PM EDT
|
Good Afternoon:
I have an AR15 n a CMP type configuration (Stainless free floating barrel, NM sites, full stock) that does not lock back on the last round, regardless of what load or magazine that I use. I built the gun with a stripped receiver, an A2 stock from a gun show, an NM upper. Sort of a parts mix master, if you will. Using factory, 55's ss109's, Remington match ammo, does not matter. the bolt closes after the last round was fired, and does not lock open regardless of mag size or design. A guy at the range was telling me that there are different recoil springs and buffers depending on if the gun is to be used as an M4, another caliber, etc. My buffer is plastic, and I have no idea what the spring length/weight is; or what it is supposed to be. I want to shoot 55-75 grain match bullets in CMP competitions. Can someone school me on what type of spring and buffer I need to have?. I appreciate your assistance. Regards, Wally |
|
You should be using a rifle length spring and buffer. Here is a link with pictures and a discussion on buffers and springs.
https://www.ar15.com/archive/topic.html?b=3&f=7&t=564656 I'd also check the bolt catch and ensure it moves freely, if it is to tight the mag follower/mag spring doesn't have enough upward push to activate the bolt catch. |
|
I have never heard of a plastic buffer, but that doesn't mean they don't exist and work, and I am not sure it would cause your problem either way.
If on an empty magazine, you pull the charging handle back, and it locks on its own without you pressing the lever, you probably have a excessive gas leakage, or a gas obstruction somewhere. 5 7/8 appears to be the appropriate length, based on measuring the one in my A2 replica. I would try to determine a weight on your buffer. Look inside the receiver extension tube to make sure nothing is inside. If it is an A1 stock instead of an A2 stock, and you are using the A2 screw, it will be too long and prevent the buffer from coming all the way back. When you fire the rifle, how far and in what direction does the brass eject? |
|
Quoted:
Plastic buffer? Red flag right there, major red flag. Pics of buffer, please. This. Only the bumper at the end should be a plasticy/rubbery material. The rest of the buffer should be metallic. Might want to pick yourself up a new rifle spring/buffer from a reputable vendor even though the spring length is in spec, if it came as a pair with a plastic buffer, I wouldn't run it either. |
|
Clean and properly lubricate everything.
Pull the charging handle as far back as it will go. There should be an1/8 to a 1/4 inch or so of the bolt visible in the ejection port. Obviously the face of the bolt should be behind the bolt catch and with an empty mag inserted the BCG should lock back hand cycling. The TM which is available on the site will list the allowable spring lengths. If it gets a lot harder to pull back the last inch or so then you may be binding on the hammer. If all of this stuff is ok put one round in the mag and fire it with someone watching the BCG. If the BCG does not go back far enough when firing you will need to start troubleshooting the gas system. |
AR Sponsor