LR308 not ejecting/feeding – advice needed

[pazmaker]

I have a DPMS LR308 that is not reliably ejecting/feeding next round. It probably works about 75% of the time. I need some advice on what to tweak to make it 100% reliable.
Here's what I have:
DPMS LR308 using factory Remington 150grain 2820 fps muzzle velocity ammo.
ODIN works adjustable gas block
Magpul 1LX50 adjustable 6-position stock with a 7" long buffer tube
2.5" long buffer weighing 3.7 oz (unknown make)
11" long spring (heavybuffers.com) 28 coils & 0.072" wire (the spring it replaced was 11.5" long 29 coils & same wire).

Is this the right spring? It takes a great deal of effort to lock the bolt back.

What should I change to ensure 100% reliability?

[Armed Eye Doc]

If you got the 308 carbine buffer spring from heavybuffer.com, it is likely OK.  You should have gotten a CAR 10 heavy buffer at the same time, 5.5 oz.  But, it could be one or both causing the issue.

[pazmaker]

I should have added that the gas block is backed out most of the way – at least 16 of the 20 click adjustment range.

Is this spring correct for a 7" long buffer tube? – 11" long spring with 28 coils & 0.072" wire.

[pazmaker]

Does some sell lighter buffer springs? Should I clip a few coils off the buffer spring?

I thought I'd get more responses here.

[Magwa]

How wet are you running your BCG? it should be dripping wet if it runs 75% of the time it sounds like a dry upper ,BCG problem...

[pazmaker]

Not dripping wet, but not dry. A light coat of of Hoppes #9 lube oil. I don't feel any dragging or rubbing. It's smooth, but the spring feels too strong.

Can someone confirm if an 11" long spring with 28 coils & 0.072" wire is correct for a 7" long buffer tube?

[DNP]

How many rounds through it so far?

[pazmaker]

Probably around 500 from me and not many from the guy I bought it from.

[DNP]

That’s enough to be broken in. Figured I’d check. It took a couple hundred before my rifle settled down and got reliable for me. They like to be pretty wet for a while, and we’ve seen a lot of issues between gas and recoil systems. I am far from an expert, but wanted to ask the simple question. We’ve seen guys trying to fix a rifle with a whole 20 rounds down the pipe.  

[pazmaker]

I think the issue is related to the buffer tube length and spring. The rifle originally had a longer fixed length ACE Skeleton Stock. Since I shoot with my son who is shorter than me, I swapped out the fixed stock for a Magpul MOE stock on a mil-spec diameter carbine buffer tube. I currently have an 11" long spring with 28 coils & 0.072" wire in a 7" long buffer tube?

[Armed Eye Doc]

@98Z5V can you verify the specs on springs?

[pazmaker]

AED, May I gently ask, what you mean by verify?

I measured the spring myself – the length with a ruler, the coil count with my finger and the wire diameter with a micrometer. I have three post-grad degrees, a fellowship and a life-long career in the physical sciences. The spring specs are dead-on.

I greatly appreciate any advice on this issue.

[Armed Eye Doc]

I mean the appropriate specs needed for proper function.  I'm not questioning your measurements.  You have asked if your spring is correct.  He will know.

I have read the info in the forum, but cannot find it.

[pazmaker]

I called DPMS today and discussed. After giving them the details I laid out in the first post, they seem to agree that the spring is the likely problem. I  purchased a DPMS spring from MidwayUSA. I'll let you know if this helps. In the meantime, if anyone has another opinion, please post.

[98Z5V]

3 hours ago, Armed Eye Doc said:

@98Z5V can you verify the specs on springs?

That spring is not correct.

On 9/30/2019 at 1:13 PM, pazmaker said:

11" long spring (heavybuffers.com) 28 coils & 0.072" wire (the spring it replaced was 11.5" long 29 coils & same wire).

Is this the right spring?

 

Slash might list that spring on his website, and says in his Reference Table that it's for his 3.0oz buffer.  There's no specs on it listed in his reference Table because it's a custom spring, per it's listing.  Since you state that you got it from heavybuffers.com, the best thing to do is call him.  There's not a man alive that knows more about AR recoil systems than him.

Here's what he lists.  For .308ARs running a 7.000" receiver extension, he recommends the Wolff XP AR15 springs, which are good, for heavier buffers. If you were running the Armalite AR-10 Carbine Extension at a 7 5/8" internal depth, his automatic answer is the Armalite spring, the EA1095.  Click the pic to make it bigger...

 

If you look at that Reference Table really close, you're gonna find something out - your buffer isn't heavy enough to run other springs.  Look at the buffer weights listed at the top of the table.  I'm thinking that spring you have is specifically made for a 3.0oz, 2.500" buffer...

Edited October 3, 2019 by 98Z5V