Thanks in advance.

New to AR15, when purchased my M&P asked for a lesson in disassemble and reassembly.

It was stressed that the Bolt must be pulled "Out" on reassembly - why?

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NRA

Its due to the rotating locking lugs on the bolt. In the "In/Collapsed" position the lugs are rotated to the locked position and will collide with the corresponding lugs on the barrel as such the bolt wont go into battery. In the out position the lugs line up with the grooves in the barrel lugs as the bolt starts going into battery. When bolt bottoms out the bolt carrier is still moving forward into the "collapsed" position which rotates the bolt lugs locking it into the barrel.


Did that make sense? I find it easier to explain in person with learning aids

Because the bolt carrier wont fit into the upper if the bolt cam pin is not in the proper orientation (which it is if the bolt is "out").

Don't worry, the AR15 platform is cleverly designed. If it fits together, it's correct. Simple as that. Things won't fit together if they're oriented incorrectly. You can't put it together wrong.

Watch a couple of YouTube videos and you'll be quickly disassembling and reassembling in no time!

This. If the cam pin isn't in place, it hits the side of the receiver instead of lining up under the gas key which then sets in the channel in the charging handle.

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SFC, US Army, Retired

Remember "out" of the carrier is "into" the barrel extension.... as others have said, you cannot put the bolt in incorrectly, the retention pin prevents it... go ahead and try it.... seriously, you wont hurt it.

The only thing you can assemble "wrong" on an AR platform is putting the bolt in backwards/upside down (Where the extractor would face away from the ejection port). This would cause some nasty jams if you did so, but probably would not hurt the rifle (unless you then cranked on the fwd assist making the jam worse) The bolt is beveled to allow the retention pin to go in easily only in the right orientation.

As others have said, you tube is your friend..... I started with the AR system in 1991, and in 2003 won our squadron competition of field strip, reassemble, function check with a time of 27 seconds....Anyone can do this, and in a while you will be able to break the rifle down in less than a minute, same for reassembly. Good luck and have fun!!!

Just put in the bolt and cross bolt then with the bolt facing down cup your hand around the carrier and drop in the firing pin. Install the cotter pin. Grab the bolt carrier by the rear portion with the bolt facing way from you and swing the assembly as if snapping a bull whip. The bolt will slide forward and be in the right position to slide into the upper receiver.

Much thanks to All - for all the good information!!

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NRA

If the bolt is out it won't fit into the barrel extension (the star chamber). When you shoot it, the bolt is out when comes forward to go back into battery. As the bolt goes back into battery the teeth on the bolt slide past the teeth in the barrel extension, and then the bolt rotates and the teeth don't line up anymore.

I agree with all the responses. I was told that if a part won't go in smoothly don't force it since you're putting it the wrong way. The only thing that can be put in wrong, but will still slide in smoothly, is the extractor, it should be facing away from you [with the gas key facing upward] during re-assemble of your bolt carrier group [BCM].

Good luck, be safe and have fun with your toy.

Happy Labor Day all! Don't burn your steak!

so true...

27 seconds? Holy moly!