DPMS LR308 Upgrade Problems

Discussion in 'Gunsmithing Forum' started by TheHateCamel, Oct 11, 2012.

  1. TheHateCamel

    TheHateCamel New Member

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    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...
     

    Attached Files:

  2. dog2000tj

    dog2000tj New Member

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    Can you toss the end cap that is just behind the gas block? :confused:
     

  3. TheHateCamel

    TheHateCamel New Member

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    Unfortunately, no I can't :( This is one of the two things helping to hold this two-piece forend together...
     
  4. dog2000tj

    dog2000tj New Member

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    any reason why you went from the 1 piece free float to a 2 piece? :confused:

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

    does the new 2pc rail fit with the original gas block? :confused:
     
  5. SSGN_Doc

    SSGN_Doc Well-Known Member

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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.
     
  6. willfully armed

    willfully armed New Member

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    Close.

    Take it to 30. Back off a turn, then take it to the next opening, not exceeding 80#.
     
  7. Jpyle

    Jpyle New Member

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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
     
  8. TheHateCamel

    TheHateCamel New Member

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    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.
     
  9. TheHateCamel

    TheHateCamel New Member

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    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?
     
  10. TheHateCamel

    TheHateCamel New Member

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    Duly noted!
     
  11. TheHateCamel

    TheHateCamel New Member

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    I'm almost positive all the parts match. I ordered them at the beginning of the year, but I vividly remember making sure they were all DPMS. Especially because I took a stock LR308 and started rebuilding it.
     
  12. SSGN_Doc

    SSGN_Doc Well-Known Member

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    Your wording is much more clear than mine. Thanks for not letting me lead him astray with vaguely worded advice.
     
  13. TheHateCamel

    TheHateCamel New Member

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    For anyone who posted here trying to help, or anyone who may read this thread having similar issues, this problem was solved many months ago. I forgot about my thread, but I figure I should let everyone know what was wrong.

    I ordered the Midwest Industries two-piece aluminum forend from Brownells. Before I ordered I emailed them asking if the forend would fit my DPMS LR-308 AP4. They said that it would. By the end of this thread I was so insanely frustrated that I took it to my local 'smith.

    Turns out the forend is for a standard AR-15, which actually takes a very slightly longer carbine sized forend. This is my first actual problem with Brownells, but considering years of great service, I can't hold it against them. I've decided to keep the forend for a later AR build.

    CASE CLOSED!
     
  14. TheHateCamel

    TheHateCamel New Member

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    Update: Case not closed!

    It looks like I have spoken too soon, folks. Sorry about that.

    Just got my new LR-308 carbine-length forend in. It's exactly the same as the previous one, minus the small rail extension. Same fitting length and all.

    I'm beyond stumped on this and I'm going to take it to my local 'smith. I'll be able to update you all on this again in a few weeks.
     
  15. JonM

    JonM Moderator

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    Call midwest industries tell em what's going on they will sort it out speedy fast. Great bunch of folks to deal with. I live 20 miles from their shop.
     
  16. TheHateCamel

    TheHateCamel New Member

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    Thanks JonM! I'll see what I can't find out.
     
  17. TheHateCamel

    TheHateCamel New Member

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    LR-308 AP4 Upgrade Problem, Officially SOLVED

    My local gunsmith and I put our heads together and after much deliberation were able to determine that two-piece handguards of this type are being advertised as "LR-308 compatible", but are in fact only for certain LR-308 models such as the LR-308 Sportical (PM me if you'd like to know who is 'misleadingly advertising').

    These will NOT fit the LR-308 AP4, which is a "Free-Float ONLY Platform". There are free-float hanguards/forends on the market for the AP4, so I'll just have to end up buying a one tailored for my gun.

    Anyone know a good place to sell gun parts? I've got a few extras now :eek:
     
  18. Triumphman

    Triumphman Active Member

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    That suks, but glad you got the problem sorted.
     
  19. molonlabexx

    molonlabexx New Member

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    You possibly need to index the tube to fit with the nut. I need some more detailed pictures.
     
  20. molonlabexx

    molonlabexx New Member

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    Well nevermind!!! Looks like you got it figured out. Try Ebay or gun broker to sell the parts!