Re: Short Cycling & gas port size *PROBLEM SOLVED*
Posted: Thu Feb 07, 2019 6:44 pm
I purchased an upper from Bear Creek Arsenal and had the same issues with it not cycling. I decided to try the simple stuff first and see if I could resolve it w/o having to drill out the gas port. I removed the bottom plate of the Bushmaster magazine and removed what I guess is a lower spacer. Some folks have cut off some the spring, but I thought I would see what happened just removing the spacer. I then used some needle nosed pliers to very slightly open up the first 1/4” of the lips so the round would slightly tip. I loaded a few rounds and compared the angle to another magazine and I could see that the adjustment let the round tip up ever so slightly. I then took a fine stone grinder on my Dremel and polished the lips.
Out to the field for the test and the gun cycled perfectly.
Out to the field for the test and the gun cycled perfectly.