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KnewB


JRoss

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5 hours ago, survivalshop said:

  Send in back for a full refund if possible & start over . If not, there are plenty of ideas in this thread to help you make the rifle work reliably . We are here to help fellow 308AR owners & builders .

I want to thank everyone for the help here and will continue to work on the rifle until it is right. No plans to send it back to factory for sure.

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Fired 2 rounds today with mag installed and 1 round in mag, bolt did not stay open after fired.Took the buffer apart and found a 12.75" length non compressed spring with 39 coils that fits into a 9.5" length tube. The buffer measures 5.188" long. My powder scale is too small to measure the weight of the buffer so will check that later but it has weights inside and they rattle around if I shake it. I did order an adjustable gas block from SLR.

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Ok still waiting to get a weight of the buffer but in the mean time with the buffer assembly apart I removed the spring and installed just the buffer in the tube and screwed it into the lower. Reinstalled the upper to the lower with a mag installed. Pulled the charging handle back and the bolt locked back in open position. Looking into the threaded hole on the butt end of the tube I see the plastic of the end of the buffer and it looks very close to end of the tube, so I grab a toothpick and push on the plastic.......... the buffer does not move! So what this means is that its time to shorten the length of the buffer. I am going to knock the roll pin out, pull the plastic out and cut a half inch or so off the end and then reinstall the plastic and drill it for the roll pin.  The dumb asses at the blackthorne factory don't know jack about anything. The buffer spring did not coil bind with the factory length buffer compressed fully to the end of the tube but I will still check for coil bind after the buffer has been shortened........... And what was the reason the gas block blew apart?....... blackthorne is full of guano!

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No advice here.  Just wanted to say I really admire your persistance.  Been following this adventure from the start.  This is epic.  And, after all, this place is about building rifles, and you are doing exactly what we do here. Three cheers!  Ole'!  Hang in there!

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    The Buffer looks correct length, but not of the Spring , all the Rifle length Receiver Extensions to my knowledge are the same length. Carbines have a couple different lengths , so that should be correct .

 

 

http://www.heavybuffers.com/reference.html look at Slash's data

Edited by survivalshop
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13 hours ago, survivalshop said:

    The Buffer looks correct length, but not of the Spring , all the Rifle length Receiver Extensions to my knowledge are the same length. Carbines have a couple different lengths , so that should be correct .

 

 

http://www.heavybuffers.com/reference.html look at Slash's data

Yes buffer tubes are the same for rifles but the springs and buffers are different from what I have researched. Slash's data says for a DPMS 308 use an AR10 Buffer and AR10 spring. I did get my buffer weighed and it came in at 4.8 ounces. Next will be to get the adjustable gas block installed and go from there. At least now I know what I have as a starting reference with the buffer system.

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9 hours ago, JRoss said:

Yes buffer tubes are the same for rifles but the springs and buffers are different from what I have researched. Slash's data says for a DPMS 308 use an AR10 Buffer and AR10 spring. I did get my buffer weighed and it came in at 4.8 ounces. Next will be to get the adjustable gas block installed and go from there. At least now I know what I have as a starting reference with the buffer system.

Look at the spring length & coil count . I'll pull one of my Rifle stock springs & make a count& measurement from one of my DPMS Type rifles , they both have DPMS Springs & Buffers in them .

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The coil count on the spring I have now is 39 and the length is 12 and 3/4 inches and the wire diameter measures .076" the buffer weighs 4.8 ounces. The AR10 spring on Slash's chart is 34 coils and the length is 13 and 3/4" and the wire diameter measures .074" the buffer is 5.4 ounces. Looking at the numbers the spring rate might be close but there are special tools to measure spring rates that are very accurate and would tell the real tale of the difference in the 2.

14 hours ago, survivalshop said:

Look at the spring length & coil count . I'll pull one of my Rifle stock springs & make a count& measurement from one of my DPMS Type rifles , they both have DPMS Springs & Buffers in them .

 

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17 hours ago, JRoss said:

The coil count on the spring I have now is 39 and the length is 12 and 3/4 inches and the wire diameter measures .076" the buffer weighs 4.8 ounces. The AR10 spring on Slash's chart is 34 coils and the length is 13 and 3/4" and the wire diameter measures .074" the buffer is 5.4 ounces. Looking at the numbers the spring rate might be close but there are special tools to measure spring rates that are very accurate and would tell the real tale of the difference in the 2.

 

  I checked both my Rifle stocked 308AR's today , Your Spring looks correct , but my new build 18" , something isn't right .

- my new build 18"has 43 coils & its 12 1/4" long ( I'm having an issue with this rifle & wondering if this may have something to do with it )

- my 20" much older build has 39 coils & its 12 1/2" long ( Which is close to what most I have seen , 12 1/2  on a very well used rifle is not bad )

Both have DPMS  308 Rifle Buffers in them , so with the 18" having that many coils , it may cause issues . Spring was purchased from Brownells along with the Buffer, This looks like they sent me a AR 15 Rifle Spring !   
 We have so many Threads on the issues with Carbine Buffer Systems , I never paid any attention to the 308AR Rifle length Systems. Damn !

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1 hour ago, survivalshop said:

  I checked both my Rifle stocked 308AR's today , Your Spring looks correct , but my new build 18" , something isn't right .

- my new build 18"has 43 coils & its 12 1/4" long ( I'm having an issue with this rifle & wondering if this may have something to do with it )

- my 20" much older build has 39 coils & its 12 1/2" long ( Which is close to what most I have seen , 12 1/2  on a very well used rifle is not bad )

Both have DPMS  308 Rifle Buffers in them , so with the 18" having that many coils , it may cause issues . Spring was purchased from Brownells along with the Buffer, This looks like they sent me a AR 15 Rifle Spring !   
 We have so many Threads on the issues with Carbine Buffer Systems , I never paid any attention to the 308AR Rifle length Systems. Damn !

Maybe you can swap your older build parts into the new 18'' and see if that works better. I was at a gun shop today and they had some AR15 buffer kits on display and like you said they don't look right for an AR308. Buffer is shorter and spring looks different. 

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   I have a Tubb's , Flat Wire Spring to put in there . 

  Your Buffer should come close to the end of the Receiver Extension . Its a fine line the way this ASR's are engineered , Springs & Buffers & the Receiver Extension have to be all of the same System , be it a DPMS LR 308 type or the AR 10 . Its a balance of spring pressure /length & Buffer weight to Cycle correctly . The Buffer may contact the end of the Receiver Extension when fired , but if it does , its should be light tap & may be more with higher powered loads .

   The fact that you can lock the Bolt back shows its not set up too short & the BCG has the ability to cycle that far fiscally, when fired & it will  not Lock Back , its could be a couple of things , Short stroking can be too weak of Gas Signal , rough Chamber to incorrect components or even tolerance stacking.

  the one in the 18"

DSCN2630.thumb.JPG.0a1b15aeb814468204ae9

DSCN2631.thumb.JPG.73a813626df69ca7e1062

The one in the 20"

DSCN2637.thumb.JPG.0f7ceabf3928f72d34e49

DSCN2638.thumb.JPG.4790b1128a62bcbb4e40d

 

 

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The one in the 20" is pretty much what mine looks like.  I have been taking close measurements on buffer to end of buffer tube and it might be good to go without shortening the buffer. I received the adjustable gas block today so next is changing the old out for new.

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Jross     order you a tubbs spring...same spring for a car or rifle butt..so you cant go wrong...it just aint that hard to get one going  it aint rocket science   ...wonder if the permatex migrated ..did you clean it off of the barrel ?  you could also get you a adj carbine stock set up...sheesh thats gotta work for ya I would think    Wash

Edited by washguy
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Jross ....you do have the screw with the hole in it mounted in the top position of the stock? In the rifle stock the top screw has a hole in it to release gas.. not having that in the right place causes malfunctions so sez this article  ive only got a few ar's with the rifle stock...they all have a drain hole screw..just checked...although I dunno whether it could cause a problem like the article sez?  if that was the case there would be too many posts about why my ar doesnt work... never payed attention

http://thegunwiki.com/Gunwiki/ProcArFixedButtstockInstallRemove    

maybe your gas tube is clogged? check your gas key for position and junk too...although thats a stretch

Wash

Edited by washguy
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12 hours ago, JRoss said:

Still not holding bolt open with gas block fully open one round in mag and firing. Maybe the spring has too much pressure or too long.  More research on springs and length and pressures. I will just order 1 of each spring made hahahaha

  Does it lock back with just an empty mag. when pulling the Charging handle back all the way ?

  Do you have a 308AR Bolt Stop installed, they have a larger pad then the AR 15.

LH1630.thumb.JPG.59bb3764730fee6fa6425c5

 

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26 minutes ago, survivalshop said:

  Does it lock back with just an empty mag. when pulling the Charging handle back all the way ?

  Do you have a 308AR Bolt Stop installed, they have a larger pad then the AR 15.

LH1630.thumb.JPG.59bb3764730fee6fa6425c5

 

I was thinking this too but I couldn't remember if it had been asked in the last 8 pages lol. 

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Yes it does lock back when puling the charging handle and an empty mag installed. The bolt stop I will have to check on but it is what they sent me along with the upper. I checked the gas tube and it is not clogged and the stock screw has a hole and it clear also.

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6 minutes ago, JRoss said:

Yes it does lock back when puling the charging handle and an empty mag installed. The bolt stop I will have to check on but it is what they sent me along with the upper. I checked the gas tube and it is not clogged and the stock screw has a hole and it clear also.

 It would be with the Lower Receiver Parts group .

 How is it functioning other wise , ejecting & extracting OK ?

Edited by survivalshop
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