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Old 10-11-2012, 08:12 PM   #1
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Default DPMS LR308 Upgrade Problems

First time home gunsmithing project and first time poster. Bear with me and please have patience...

I bought an LR308 about 2 years ago, and have been making modifications here and there since then. Most recently I removed the stock muzzle brake, gas block, carry handle, and free float tube in order to upgrade them. I replaced with a Miller Precision Arms 'Hammerhead' muzzle brake, a PRI picatinny gas block, flip up iron sights, and a Midwest Industries two-piece quad rail forend. Because the original free float forend was one solid piece of aluminum, it had no barrel nut or delta ring assembly. Therefore I had to obtain and mount those in order to install the new two-piece forend. The barrel nut and delta ring assembly were both 308 parts (not AR-15), so I am pretty sure I did not make a mistake and order the wrong parts.

From the pictures, you will notice that it is obviously not cycling. You'll notice that at the gas block I have open ports on my barrel just barely showing, so everything needs to be moved back. That makes the problem at the area of the barrel nut and delta ring assembly. This needs to be moved back farther, not only to cover the ports, but also to get the gas tube properly inserted into the bolt carrier assembly.

I'm not sure what I did wrong guys. I have an idea that I could probably tighten the barrel nut on about a revolution and a half tighter, then allowing me to slide everything back just enough for the rifle to cycle properly. The problem there is that when I put the barrel nut on I had already tightened it pretty well (or at least in my opinion).

I'm concerned about tightening my barrel nut too tight. But is that even the problem here? Please tell me what you think folks...
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Old 10-11-2012, 08:22 PM   #2
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Can you toss the end cap that is just behind the gas block?

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Old 10-11-2012, 08:31 PM   #3
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Quote:
Originally Posted by dog2000tj View Post
Can you toss the end cap that is just behind the gas block?
Unfortunately, no I can't This is one of the two things helping to hold this two-piece forend together...
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Old 10-11-2012, 08:41 PM   #4
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any reason why you went from the 1 piece free float to a 2 piece?

I don't think torquing down the castle nut anymore will help, more likely to cause problems/damage

does the new 2pc rail fit with the original gas block?

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Old 10-11-2012, 09:53 PM   #5
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Is the delta ring in the right position relative to the compression spring, snap ring and barrel nut? If something is wedged in between and keeping the barrel nut from tightening against the face of the receiver then that could be your problem. It does need to be tight. 30 to 80 ft/lbs is what it should be torqued to.

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Old 10-12-2012, 12:40 AM   #6
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Quote:
Originally Posted by SSGN_Doc View Post
Is the delta ring in the right position relative to the compression spring, snap ring and barrel nut? If something is wedged in between and keeping the barrel nut from tightening against the face of the receiver then that could be your problem. It does need to be tight. 30 to 80 ft/lbs is what it should be torqued to.
Close.

Take it to 30. Back off a turn, then take it to the next opening, not exceeding 80#.
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Old 10-12-2012, 12:56 AM   #7
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Have you checked the compatibility of your upgrade parts with the LR-308? There are differences not only between the Armalite and DPMS patterns but between manufacturers.

http://308ar.com/compatibility.htm

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Old 10-12-2012, 02:29 AM   #8
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Quote:
Originally Posted by dog2000tj View Post
any reason why you went from the 1 piece free float to a 2 piece?

I don't think torquing down the castle nut anymore will help, more likely to cause problems/damage

does the new 2pc rail fit with the original gas block?
I went with the 2 piece because it allows me to remove the forend without removing the muzzle brake or the gas block.

The original gas block ends up sitting in exactly the same spot as the current one, which is why I believe the problem to be at the face of the receiver. I could keep putting gas blocks on there but it won't do any good because the whole thing needs to be slid back a little bit. Good idea, but already nixed that one.
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Old 10-12-2012, 02:30 AM   #9
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Quote:
Originally Posted by SSGN_Doc View Post
Is the delta ring in the right position relative to the compression spring, snap ring and barrel nut? If something is wedged in between and keeping the barrel nut from tightening against the face of the receiver then that could be your problem. It does need to be tight. 30 to 80 ft/lbs is what it should be torqued to.
The delta ring, compression spring, and snap ring are all A-OK, but I'm thinking I'm going to take it apart and try tightening again. I didn't use a torque wrench the first time, so do you think that's why?
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Old 10-12-2012, 02:31 AM   #10
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Quote:
Originally Posted by willfully armed View Post
Close.

Take it to 30. Back off a turn, then take it to the next opening, not exceeding 80#.
Duly noted!
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