New AR 10 6.5 Creedmoor Build

[Cenius85]

I need help with a 6.5 creedmoor build.
22" Odinworks 6.5 Creedmoor +2 barrel with an Odinworks AGB.
Luth AR Rifle length Buffer and spring.
Recoil Technologies BCG
First off it took me a while to figure out the the AGB had 2 screws in the same hole but I got figured out. I can get the rifle eject rounds but it wont lock back after the last round. I messed with the gas to the point that I think I was over gasping it because the primers were almost perforated, but the bolt wont lock back. Sometimes it would lock back on the carrier but not the ejector, I didn't get pictures of it to show. I can manually cycle it just fine. I've heard that sometimes the Luth Ar rifle springs are too long but I was hoping for some better insight. Thanks for any help!

 

[Mike_in_FL]

I would try to re-adjust the gas and probably a different magazine. Whose receivers and what mag are you using?

 

[Cenius85]

I'm using a pmag magazine, and I have adjusted the gas. I started from fully closed and then slowly opened it up. I dont have a brand for the receiver, the upper receiver is

DPMS Style LR-308 Forged Upper Receiver Low Profile Gen 1 LR308 AR10 AR-10. The lower is an 80% lower

 

[Mike_in_FL]

If it is truly needs more gas I would measure the gas port to see if it's at least .086. Or contact Odin and see what they say. Otherwise for a quick and dirty test I'd pull some weight out of the buffer and shoot it again.

 

[Cenius85]

Ok, I'll see if I can figure out how to remove weight from the buffer. You dont think it's an issue with the spring, i only ask because i have read about the Luth AR rifle springs being too long.

 

[Mike_in_FL]

You knock out the roll pin that holds in the polymer end to remove weights or change to tungsten, whatever. I have no idea about the Luth AR spring. Go to heavybuffers.com and look at Slash' photos of the lengths of springs and see if you think yours is in spec. Otherwise I would buy a Tubb AR10 spring.

 

[Mike_in_FL]

Ok, I'll see if I can figure out how to remove weight from the buffer. You dont think it's an issue with the spring, i only ask because i have read about the Luth AR rifle springs being too long.

Although if it were too long I would suspect coil bind type of situation and it not locking back manually

 

[Cenius85]

Ok, that makes sense, I can manually pull it back fine. I'll try and mess with the buffer. Thanks for all the help.

 

[drew_eckhardt]

How long is your buffer?

A .308 rifle buffer should be 5.2" long versus 5.9" for a standard AR-15 part.

.308 buffer +spring rightmost,standard AR-15 second from right

 

[Rancid Coolaid]

Rule #1 with large-frame AR break-in: when you think you have way too much lube, you almost have enough lube.
That, and I just like to say lube.


Lube.

 

[Cenius85]

The buffer is 5 5/16" long. How many weights should I take out to test it?

 

[msgriff]

You may have bigger, more serious issues if you're showing over pressure signs, such as cratered or pierced primers. DI gas systems, whether over or under gassed, has no bearing on chamber pressure. I would accurately (+/- 0.001") measure your bolts firing pin aperture, firing pin tip diameter and firing pin protrusion. Headspace should be checked if you haven't done so already. Ammo should be looked at, especially if it's handloads. Premature unlocking of the bolt can be an issue, but a 22" barrel with +2 gas usually rules that out. Make sure the gas block is properly aligned over the port. The gas tube should end at the center of the cam pin cut-out. A standard .308 riffle length buffer should weigh around 5.4 oz. Removing weights alone will adversely affect the reciprocating mass design of a buffer. Contact Heavy Buffers if you want the best expert advice concerning buffers. Same for springs, or ask DTubb. Check the condition of the chamber, rough or oily chambers can significantly increase required cycling force. Check the distance between the bolt face and the bolt catch at full pull back of the charging handle. There is an easy, accurate way to do that if you wanted details. I shoot for 0.150" to 0.200" clearance. Overgassed and undergassed conditions can be easily confused.

 

[Cenius85]

I only had primers that looked closed to pierced once the gas was all the way open. When I was increasing the gas the primer strikes were normal. I know that the AGB is on center, I removed the AGB once and the gas soot was in an even circle around the gas port.

 

[bfoosh006]

Just to be clear, you can manually lock back , via the charging handle, the BCG ?

To be honest, 5 5/16" is 5.3125".... and that might be a little long for your buffer tube. I am pretty sure .308 Rifle length buffers should be right around 5.2". And I could be wrong...

It might manually lock back, but when cycling upon firing, the buffer might be bouncing off the bottom of the buffer tube, and not allowing enough time for the bolt catch to keep up.

 

[Mike_in_FL]

The buffer is 5 5/16" long. How many weights should I take out to test it?

I would only take out one just to test function. I know someone commented about the appearance of your primers. I'm not familiar with that brand of BCG you have. It is rather well known that if it is a normal .308 BCG it most likely has the larger diameter firing pin rather than the .062 that comes in the JP high pressure bolt (and all the Armalite AR10 BCGs) and are preferred for 6.5 rifles due to cratering.

Look at this, https://www.midwayusa.com/product/1019429229 and read the 1st review. Yes, you should have checked headspace with gauges to truly be safe but I think it's rather rare these days to have a problem.

 

[Cenius85]

Duplicate message...

 

[Cenius85]

I purchased go no go gauges before using it, I'm a bit of a worrier and didn't want a catastrophic malfunction. It locks and fires fine. Like I said I only saw more dented primers once I fully opened the gas. And even then the primers didn't actually get pierced. I'll look at the bolt you linked. Another question i have is what is the best way to measure the diameter of the gas port?

 

[msgriff]

I purchased go no go gauges before using it, I'm a bit of a worrier and didn't want a catastrophic malfunction. It locks and fires fine. Like I said I only saw more dented primers once I fully opened the gas. And even then the primers didn't actually get pierced. I'll look at the bolt you linked. Another question i have is what is the best way to measure the diameter of the gas port?

Pin gauges are the standard for measuring, but a numbered drill bit set will work. Use the shank, then measure the shank with a micrometer or caliper, as the shank can be a different diameter than the number equivalent.

 

[DavidAR10]

I haven't seen one mention of the make/model of buffer tube.

All of my stocks are Magpul, and only my UBR stocks come with a buffer tube.
Clint at Heavy Buffers gets all of my buffer/spring money for 308/6.5mm rifles. {ARMALITE/AP}
Oh, and for my 458, 375 & 358 SOCOMs.

I just email him with all the facts.

 

[Cenius85]

The make of the buffer tube, spring and weight are from Luth AR, Luth-AR AR .308 A2 Rifle Buffer Tube Assembly Aluminum Black BAP-308 (RS)

 

[DavidAR10]

The make of the buffer tube, spring and weight are from Luth AR, Luth-AR AR .308 A2 Rifle Buffer Tube Assembly Aluminum Black BAP-308 (RS)

Thank you, sir.
Now...
Call Saul Clint @ Heavy Buffers. His counsel is free.

 

[Cenius85]

Just wanted to give you guys an update, I finally got to go out shooting again. I bought a Tubbs flat wire spring and it seems to have fixed the issue. The rifle is cycling great, used different mag brands, shot a full mag too and it ran great. Only thing is it seems like 1 in 10 primer strikes was harder than the rest. I didn't have any pieces primers but you can tell the strike hit harder. So I'll look at getting a high pressure bolt in the future. Thanks for all the help everyone.