What do I have here? Also, why is it short stroking?
I received this gun in a trade. It is my 1st AR-15. I was told it is a Bushmaster upper on a Surplus Ammo and Arms lower. The Barrel is marked B MP 5.56 Nato 1/9. After some research I found that that stands for Bushmaster Magnetic Particle Tested 5.56 Nato is what the gun is chambered in, and 1/9 is the twist rate of the barrel.
So, I took the gun out to shoot it for the 1st time and took a few different types of ammo with me:
5.56 Nato Federal m193 ball
.223 Winchester White Box
.223 PMC
.223 Wolf steel case ammo.
After trying all of these ammo's out, the only type that would cycle 100% all the time is the 5.56 Nato m193 ball. The other's were hit and miss:
5.56 Nato = 100%
Winchester White box = 50%
PMC = 40%
Wolf would not cycle at all. Short stroke every time.
By Short stroke I mean it would eject the spent casing, but not pick up a new round. Sometimes it wouldn't even eject at all.
WTF? I'm not totally dissatisfied with the rifle, because it will cycle the 5.56 rounds 100% of the time, so that's what I stocked up on. It would be nice to be able to shoot the cheaper ammo from time to time.
So, I disassembled the gun and got out the measuring tape , and here is what I found.
Barrel is 17 1/8" to the end of the flash suppressor
16" to the beginning of the flash suppresor.
The buffer spring has green paint on it, and measures 11 1/4" long.
The Buffer has no Markings on it of any kind.
Pictures of the rifle assembled and dissasembled can be found here:
http://s1121.photobucket.com/albums/...enny775/AR-15/
After a little searching, I am thinking that the Buffer spring and buffer may be incorrect.
It should also be noted that the guy I got the rifle from said it was built by a local law enforcement officer who is also the Armorer and Sniper for the local swat team, and that he knows what he is doing.
Any ideas?