LR308 Home Built Problemo

[txchl]

I asked this question in an old post and was asked to write it in a new post, BUT if someone will answer a few questions, I'd appreciate it.  I have a home built LR-308.  It worked great till I installed an adjustable gas block (or I thought it was working.)  it has a 20" barrel with rifle length gas tube and an adjustable stock.  While cleaning I noticed my buffer retainer is bent, see attached.  I have a tube extension measuring 7.75" with a 308 spring and a 3.25" long buffer.  Rifle shot fine with a solid gas block, well I didn't notice anything bent.  NO, the end of my BC is not being marred.  Yes, when I close the upper to lower the BC end does move the buffer face back some.  As a side note, with the new gas block my BCG does not lock with empty mag AND 14 times out of 16 single shots the spent case would not eject......

1. how long should my buffer tube be?

2. how long should my buffer be and how much should it weigh?

3. how many rings should my buffer spring have on it and how long should it be?

Thx for any help, my old gas block is standing by.

Edited October 7, 2015 by txchl

[98Z5V]

I think I responded to this in another thread - hit your other thread.

Copy your OTHER post into this thread, man.  Just quote yourself, on that one, and paste it here...  That'll help alot...

 

Edited October 7, 2015 by 98Z5V

[98Z5V]

1. how long should my buffer tube be?

2. how long should my buffer be and how much should it weigh?

3. how many rings should my buffer spring have on it and how long should it be?

Thx for any help, my old gas block is standing by.

 

 Those are the details that you need to give us, on your current configuration...  Tell me how long your buffer tube is, internal length. Tell me how long your buffer is, and how much it weighs.  Tell me how long your buffer spring is, and how many coils it has. 

 

Help me, help you...

Edited October 7, 2015 by 98Z5V

[blue109]

Just to be clear...this is a DPMS brand lower?

[txchl]

1. how long should my buffer tube be?  7.75" inside depth

2. how long should my buffer be and how much should it weigh?  3.25" long, 5 oz

3. how many rings should my buffer spring have on it and how long should it be?   11.45" long with 29 rings

4. The lower is a DPMS Gen 1 Pattern Compatibility, the upper is a Arms Unlimited DPMS High Rise.

5  The buffer face has some marring around the edge where the retainer was chewing on it.

Edited October 7, 2015 by txchl

[survivalshop]

  I would like to see a photo of the Receiver Extension ( Buffer tube ) & the Lower receiver where they meet the Retainer pin .

- 7.75" is a little long for a DPMS Receiver extension , 7" is normal & DPMS type rifles take a std AR 15 Carbine Extension (Tube ) which is normally 7" 

-29 coils is what I have for a 308 Carbine spring & normally around 11 1/4- 11 1/2 , so your not far off there 

- a DPMS Carbine buffer is only 2.5" long & aprox. 3,325 oz. , you have a AR 15 one , it looks like.

Some use Armalite AR 10 Buffer system in their DPMS rifles & you could have some of its components in there , but the spring . Others here that use that system ( it uses the AR 15 Buffers ) can say more about it . I don't use that system on my DPMS rifles , myself .

 I would also like to see a photo of the BCG in breach locked position & how far it prudes from the Upper Receiver , with the Upper Shot Gunned , so we can see it from the side & back , please 

Edited October 7, 2015 by survivalshop

[washguy]

TXCHL   you stated it was working or so you thought till you put on the adj gas block...sooo lets go back to square one

shotgun open the rifle muzzle pointed down and drop the handle with the bcg in....the bcg should just bout go into battery...what your checking is to see if theres any interference with the gas tube and gas key...you could have it off a lil ...get the gas tube aligned with the key first off...and adjust the gas block making sure it is aligned with the port on the barrel and not leaking either. on the problem of it beating the pin up and it not locking back...you said as a side note you dont lock back and you have a single shot...thats not a side note thats major unacceptable stuff right there....why did you put the longer buffer tube in and the ar15 buffer? If it was me i would go back to square one on that too....ar15 buffer tube,ar308 buffer,and ar308 buffer spring...its a cheap experiment that could help solve your probs... need to see if the bcg is taking the buffer off the pin too when closing the upper to lower    Wash

[txchl]

Wash

first, Thx for replying.  Yes the non ejecting is major.  My original question was:  (should have added for a LR-308)

1. how long should my buffer tube be?

2. how long should my buffer be and how much should it weigh?

3. how many rings should my buffer spring have on it and how long should it be?

I think when I put my rifle together I used the wrong parts to begin with.  I will check and take pix of the bolt and breech.  I am 90% sure the BC is contacting and pushing the buffer back when closing the two receivers.   THANK You for help.

jd

[washguy]

TXCHL   did you drop in the bcg and charge handle to see if it goes into battery and then do the blow test....plug up the chamber wrap your mouth around the muzzle...yes I know it tastes good...give it a blow and with your finger inside near the gas tube...you feeling the air? Of course you can use compressed air,but its more fun to get personal with your muzzle

So, if your gb is centered over the gas port and your gas tube is aligned and your bcg almost falls into battery...and you got air coming out the gas tube inside the upper....get an ar15 car tube...whichever one fits your stock...mil or commercial...and not one off ebay...and dont get any enhanced type buffer tube either...get a dpms ar308 spring... dpms ar308 buffer.. and as new buffer retainer pin and spring...why be concerned about lengths? if you get the correct parts its all taken into account for you ..if you get the correct pieces...how did you arrive at the incorrect parts that are in there now?  just checked some of my 308's all of them have the bcg coming out farther from the upper than your pics...although pics can be deceiving...but the pin being bent is what Shibi sez prolly

and open up the adj gas block to start off with      Wash

Edited October 7, 2015 by washguy

[shibiwan]

Looks like an issue with the BC assembly. When fully assembled, the BC should push the buffer back by a tiny bit so it doesn't rest on the buffer retaining pin. Could also be upper receiver related too (probably a result tolerance stacking between the lower and the upper) that is causing the BC to be too far forward during firing. Bottom line; with the bolt carrier group fully forward, it should still contact the buffer. Those circumferential marks on the face-edge of the buffer indicate it's slamming into the buffer retaining pin when it's cycling and with proper BC/buffer contact those marks should never be seen.

Edited October 7, 2015 by shibiwan

[txchl]

Wash

It passed the blow test and gas tube appears to be aligned perfectly (blind in one eye, can't see out of the other...).  I am going to purchase another tube, buffer and use the same spring (I got extras).  I will do all this in the coming weeks and will update all.  Thx ALL for help

Shibiwan

After I install all the parts listed above, I will continue to watch the retaining snertzle and BCG rear end for wear.  Are you saying the BC is too long or my receivers are not compatible?

No matter, the beat goes on.

Keep your powder dry, hussein continues to want our weapons.

jd

 

[shibiwan]

Shibiwan

After I install all the parts listed above, I will continue to watch the retaining snertzle and BCG rear end for wear.  Are you saying the BC is too long or my receivers are not compatible?

 

It looks like the BC is too short, or it could be that it's seated too deep in the receivers. The latter could be because of tolerance stacking between the upper and lower. Was the upper/lower a matched set? 

From the "ring" of marks on your buffer, it looks like it's being stopped by the retainer and not being stopped by the BCG when the BCG is fully forward.

Edited October 8, 2015 by shibiwan

[washguy]

Shibi's on it  bc is too deep into the upper...all of my bcg's  are longer just a smidge...yours is not...I dont see how your bc can contact the buffer when closing?     Wash

[shibiwan]

3rd possibility is the hole for the retaining pin is off by a hair too close to the rear so the buffer face doesn't "stick out" enough.

[98Z5V]

1. how long should my buffer tube be?  7.75" inside depth

2. how long should my buffer be and how much should it weigh?  3.25" long, 5 oz

3. how many rings should my buffer spring have on it and how long should it be?   11.45" long with 29 rings

4. The lower is a DPMS Gen 1 Pattern Compatibility, the upper is a Arms Unlimited DPMS High Rise.

5  The buffer face has some marring around the edge where the retainer was chewing on it.

 Those are Armalite AR-10 numbers, and they're slightly off the real numbers - where did you get those numbers from?  And, is your recoil system complete, 100% Armalite AR-10 Carbine recoil system parts?

7.75" internal depth of the receiver extension is off.

#5 shows that you are NOT pushing the buffer off the retainer when the upper is closed on the lower.  Classic symptom, and exactly what happens, when this does not occur.

[survivalshop]

 The Receiver Extension doesn't look right also , that ramp or anti tilt extension on it, is in a strange position . The anti tilt ramp should have a cut out for the Retaining pin & its position should be lined up in such a way that the Collapsible Stocks guide & latching area would be in line . That one looks odd.

  We have seen Receiver sets not made or designed to work with all others , its why we use the Term " Tolerance Stacking " . If your BCG is not pushing the Buffer back a little , your Buffer will , as said , beat up the Retaining pin & the Buffer face . 
  We have been through this before , get your Buffer system with the correct parts , be it a DPMS or a complete AR 10 systems & if you still have a problem with the Retaining pin , you can go to a Tubb's  Bolt Carrier weight system to add some length to the BCG to push back the Buffer, off the Retaining pin . 

  I would start as said , with the correct Buffer system & see how she works , I think you will find the action will work much better .

I asked this question in an old post and was asked to write it in a new post, BUT if someone will answer a few questions, I'd appreciate it.  I have a home built LR-308.  It worked great till I installed an adjustable gas block (or I thought it was working.)  it has a 20" barrel with rifle length gas tube and an adjustable stock.  While cleaning I noticed my buffer retainer is bent, see attached.  I have a tube extension measuring 7.75" with a 308 spring and a 3.25" long buffer.  Rifle shot fine with a solid gas block, well I didn't notice anything bent.  NO, the end of my BC is not being marred.  Yes, when I close the upper to lower the BC end does move the buffer face back some.  As a side note, with the new gas block my BCG does not lock with empty mag AND 14 times out of 16 single shots the spent case would not eject......

1. how long should my buffer tube be?

2. how long should my buffer be and how much should it weigh?

3. how many rings should my buffer spring have on it and how long should it be?

Thx for any help, my old gas block is standing by.

You say the rifle shot fine with a std gas Block , then you installed an Adj. gas block & you started to have function problems ? Have you adj. it correctly ?

 The bending of the Retaining pin may have took a while to beat it up .

 

Edited October 8, 2015 by survivalshop

[breastroker]

POF makes a 7 position 308 buffer tube that allows using standard AR 15 type buffers. They call it anti-tilt but I like the fact the end of the carrier rests on the buffer tube and not in front of the retainer/tube.

 

One thing I thought I noticed is there isn't the gap usually needed by barrels and the gas block, should be about 2 business cards thick. You could have the barrel hole partially covered.

[washguy]

Breast  he has already checked for proper alignment by using air down the barrel and out the gas tube while the chamber is plugged...the pof buffer tube is not what he needs now while sorting out his problem    Wash

[blue109]

Save complicated unnecessary "upgrades" for after you get the gun running.

Many lopro gas blocks are designed to sit right up against the shoulder. Not many people use a handguard cap with them.

[shibiwan]

New buffer, spings, etc  won't solve the problem if the BCG is too far forward to push the buffer off the retaining pin. You're just going to be throwing good money after bad and ruining a new buffer in the process. Double check the BCG length and see. I think I may have an idea that I could make on the CNC that could potentially solve this type of issue...

[Wolfgang1952]

I had the same problem with my LR308A2 carbine I built.   To solve my problem we chucked the buffer up in a lath and cut a shallow step around the face of the buffer.   The step allowed the buffer to travel just forward enough to touch the BCG.    Your BCG wants to push the buffer back into the buffer tub when you close the upper and lower.   The only time the buffer rest againts the retainer pin is when you open the upper.   We found that the buffer retainer detent wasn’t in the right place.    It was holding the buffer to fore back, not letting it rest against the BCG.

 

Wolf

Edited October 9, 2015 by Wolfgang1952

[survivalshop]

New buffer, spings, etc  won't solve the problem if the BCG is too far forward to push the buffer off the retaining pin. You're just going to be throwing good money after bad and ruining a new buffer in the process. Double check the BCG length and see. I think I may have an idea that I could make on the CNC that could potentially solve this type of issue...

He already said the buffer is being moved by the BCG & if you look at what he has for his Buffer system , there are some wrong miss matched components .?

 Yes, when I close the upper to lower the BC end does move the buffer face back some. 

[txchl]

Men

When I put this weapon together originally, I had to use a buffer tube that was 7.75 inches long for the bolt to clear bolt release catch.  That's why my tube is longer, but the water is not cold.  I'm with shibiwan, my bc is not pushing back the buffer when it is fully seated, even though it touches it when I close the two receivers.  So I need a light weight insert that goes into my bc that sticks out the back 1/8" or so that will clear the buffer off the retaining pin.  OR I need to take this paper weight and chuck it.  Crap.  Shibiwan see attached pix of the bcg for lengths extended and collapsed.

[washguy]

You still need the proper buffer tube ,buffer and fresh spring......Wash

[txchl]

Wash

IF someone could tell me exactly which buffer tube, buffer and fresh spring to purchased it would be done soonest.  That was my original question.  I think I have proper tube and spring.  I think my buffer is incorrect and my bc is incompatible with my upper/lower.  BUT I haven't been paid enough to think since 5/2007 when I was injured in Tikrit......

I know a local gun smith here in Abilene, I will take weapon to him and ask some questions.  Thx to all and I will update when proper function is achieved.  Have a good weekend.