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View Full Version : Loose barrel in upper?


tgriffin
12-26-2007, 9:41 AM
All,

Please let me say thank you in advance, I appreciate the wealth of knowledge everyone here has to offer.

This is a bushmaster carbon-15 upper with approx. 1000 rounds through it. The only changes that have been made to it was replacing the bird-cage flash suppressor with another compensator, which I did myself at home.

I was having terrible accuracy, having to move the recticle or BUIS all the way to one side or another (intermitantly) to get accurate shots down range.

Then one day, I was cleaning around the comp with the grip and stock held firmly between my knees. As I applied pressure to the front sight, the whole barrel assembly moved within the receiver! In other words, I was and am able to wiggle the properly secured front sight/gas block (and ergo the entire barrel) while the upper receiver and lower receiver assembly remain stationary. I think I found out what was causing my accuracy issues. I have an armorer's wrench, and could not tighten the multi-toothed "lock ring" that was exposed upon removal of the handguards.

So all that being said, what does my issue appear to stem from?

Ryan HBC
12-26-2007, 10:39 AM
You will have to remove your gas tube before you can tighten the barrel nut, but it sounds like your barrel's indexing pin is damaged, or the upper itself where it meets the pin is damaged.

You better wait until someone familiar with those carbon uppers chimes in.

Sydwaiz
12-27-2007, 5:50 AM
Or it's just loose! I had the same problem on my Eagle Arms a few years back after a couple thousand rounds. I think during assembly, they put them on hand tight and if it indexes properly, they leave it. I just did some barrel work on a friends DPMS bull barrel upper and the barrel nut was barely tight. I don't think it would have even been the minimum 35lbs, it came off so easy. Also aluminum does stretch a little so it may have been tight to begin with and just loosened up with time.

OutlawDon
12-27-2007, 8:19 AM
Or it's just loose! I had the same problem on my Eagle Arms a few years back after a couple thousand rounds. I think during assembly, they put them on hand tight and if it indexes properly, they leave it. I just did some barrel work on a friends DPMS bull barrel upper and the barrel nut was barely tight. I don't think it would have even been the minimum 35lbs, it came off so easy. Also aluminum does stretch a little so it may have been tight to begin with and just loosened up with time.


Same problem right now on my recently purchase DPMS 20" bull barrel upper. The free float tube was loose, and with the bipod on the bench it would twist left and right slightly. Only thing holding it on was the gas tube. Very annoying. I took the gas tube off to tighten it, and the bipod stud was off center at least 10 degrees. How the heck am I supposed to use the bipod now?! Someone at DPMS didn't torque it to spec! I am getting a JP V-tac tube so I can tighten the barrel nut, and still have the stud be centered. I noticed my barrel was ever so slightly loose with the tube so loose. That explains why my groups were all over the place and around 1.5" with good ammo! Grrrrrr!

tgriffin
12-27-2007, 2:00 PM
I am hopeing that AR15barrels will chime in here with some advice. If I cant figure out whats going on with it I might just send it down to him.

ar15barrels
12-27-2007, 9:27 PM
I don't know where C.C.C. is, but you need to come see me. ;)
As others have already mentioned, the factories do slip-up from time to time and let one get out without a tightened barrel nut.
Hell, I left a LaRue locking ring loose on an upper that I was sending to compare against other makers of custom 6.8 uppers. :eek:

ar15barrels
12-27-2007, 9:31 PM
Same problem right now on my recently purchase DPMS 20" bull barrel upper. The free float tube was loose, and with the bipod on the bench it would twist left and right slightly. Only thing holding it on was the gas tube. Very annoying. I took the gas tube off to tighten it, and the bipod stud was off center at least 10 degrees. How the heck am I supposed to use the bipod now?

A $10 pack of my barrel nut indexing shims would have fixed that upper. ;)

tgriffin
12-30-2007, 9:42 AM
I don't know where C.C.C. is, but you need to come see me. ;)
As others have already mentioned, the factories do slip-up from time to time and let one get out without a tightened barrel nut.
Hell, I left a LaRue locking ring loose on an upper that I was sending to compare against other makers of custom 6.8 uppers. :eek:

About 375 miles away ;). I'd still like to send it to you. Please PM with details.