ar10 bcg compatiblity

[Ketamine0815]

Afternoon Gents. I'm new to the forum here, and new to the .308/7.62 as well. I have built several ar15's with no problems. So I spec'd everything out on this dpms pattern ar10. Upper/lower is Falkor Defense and I have a KAK double ejector that works pretty good. Was looking online and found a sweet deal on a Lantac ebcg. Figured it would be a nice backup and I have one for my 5.56 that works awesome. Well wouldn't you know it won't fit? when I pull the charging handle back it seizes up and gets stuck, have to use forward assist to back out to get it loose. I don't get it.  Any help would be appreciated. I am new to 7.62, and tried to get everything to jive. Am I wrong to think it should fit? Thanks in advance

[survivalshop]

  

5 hours ago, Ketamine0815 said:

it seizes up and gets stuck, have to use forward assist to back out to get it loose.

  That statement needs some clarification . Are you forcing the BCG back into battery to get it to loosen it up ?

 

Edited October 5, 2017 by survivalshop

[Ketamine0815]

sorry if my writing is confusing. the bcg moves with no problems in and out if the upper receiver when i have the upper receiver disassembled from the lower receiver. when i assemble the upper and lower back together and  pull the charging handle back, the bcg gets stuck. the bcg only makes it about half way of what it should before it would normally lock to the rear. when it gets locked in this position i have to use my forward assist the get the bcg to move forward

 

[MrPaul]

You may have a buffer tube issue. Are you useing a commercial or mil spec buffer tube. I think the inner diameter is smaller on one of them.  No expert on the subject here but that's the one thing I can think of that would cause a bolt carrier to get stuck half way back. Another is the little nub on top of the charging handle tip where it meets your gas key.  Is that rubbing on the inside top of your upper receiver when you pull it back?

Edited October 5, 2017 by MrPaul

[jtallen83]

Check the forward assist pawl. I tried to use one that was supposedly made for 308 AR's that had a longer pawl, it jammed up the carrier but did it much sooner than half way back. Could be your FA and that carrier don't play well. 

Pretty sure the inside diameter on buffer tubes is the same for commercial and military, the outside is where they differ.

[survivalshop]

  Remove the Hammer & see if it still gets stuck & you did say the one with the duel Extractors worked OK , right ? 

 

 

All Receiver Extensions ( Buffer Tubes ) have the same inside diameter , its the outside diameter. thats different from the Milspec & Commercial . The Length of the different Receiver extension can have a subject all on its own .

[edgecrusher]

What buffer and spring are you using? 

 

And by the way, AR10 nomenclature refers strictly to Armalite rifles. You sir are building (and for the first time it needs to be specific because there are compatibility issues with mixing and matching) a 308Ar in DPMS pattern.

 

 

and you’ll find tolerance stacking with that pattern parts by mixing manufacturers.

[98Z5V]

On 10/5/2017 at 9:42 AM, MrPaul said:

You may have a buffer tube issue. Are you useing a commercial or mil spec buffer tube. I think the inner diameter is smaller on one of them. 

This is not correct info.  The outer diameter is different (1.14" on Milspec and 1.17" on commercial), as well as how the threads are made.  Threads are cut into a commercial carbine receiver extension.  Threads are rolled on a milspec carbine receiver extension.

Here's a over-exaggeration of the threading - but it drives the point home.

 

Just wanted to clear that air right away... 

[MrPaul]

On 10/7/2017 at 10:11 PM, 98Z5V said:

This is not correct info.  The outer diameter is different (1.14" on Milspec and 1.17" on commercial), as well as how the threads are made.  Threads are cut into a commercial carbine receiver extension.  Threads are rolled on a milspec carbine receiver extension.

Here's a over-exaggeration of the threading - but it drives the point home.

 

Just wanted to clear that air right away... 

I stand corrected.