Multiple Malfunctions - Help

[Sarugo]

Hello all,

New to the forum. If this is the incorrect location for a technical troubleshooting post, apologies. Thanks in advance for everyone’s replies.

About me and about the build in question: I’ve built a few AR 15s before, but never an AR 308, this was my first one. Relevant parts are as follows… Aero M5 upper, Odin Works 6.5CM 22” barrel with tuneable gas block and XL gas tube, Ballistic Advantage BCG, Vltor A5 buffer tube, H3 buffer(came out of a previous AR15 build), Sprinco Red buffer spring. Didn’t have upper vise so I delicately clamped the upper btwn 2 pieces of wood for the barrel install, needed to use shims for Aero’s barrel nut and they got kinda crumpled but I used ‘em anyways, barrel extension was a sloppy fit so I bedded it with stainless shims and green loctite. Torqued to 70 ft/lbs.

Took it to the range for the first time yesterday… spoiler alert… it went poorly. I preset the tuneable gas block to almost fully closed. Fired one round of 140g Hornady Atypical soft point and to my surprise the round extracted and ejected(bot did not lock open),upon inspecting the brass the primer had sort if prolapsed(pic below). I continued to fire more of this same round while gradually opening the gas block… got more prolapsed and even pierced primers, but the bolt never locked open on empty, even with the gas block fully open(the bolt locks open just fine manually).
In the 20 rounds I experienced a few failure to extracts and a few very weak ejections. I also had the bolt jam closed twice on a live round and once on an empty chamber. I switched to 147g Hornady match and with that round the primers looked just fine after firing, but I got multiple failure to extract and the bolt still wouldn’t lock open. Fired about 30 rounds total

Back home I disassembled to rifle to see what I could see, some notable things are as follows…. Firing pin retaining pin was bent and looks like it took a beating, buffer has some marks on the face from hitting the buffer retaining pin, lots of pierced primer bits fell out of my bolt upon disassembly, BA apparently used 2 o-rings on the extractor spring(could be a manufacturing error or intentional) which made the extractor absurdly stiff, firing pin has some carbon that I can NOT get off with solvent and scrubbing(never seem this before), one bolt lug has a small nick, extractor seems pretty rounded off.

I have not had the bolt/barrel extension headspaced and I know I should do that.

Any thoughts or diagnostic tips that y’all could offer would help greatly for my next trip to the range. From my basic understanding of AR malfunctions I am confused by the combo if malfs that I’m seeing here. Again, any “if this then that” type diagnostic tests that I could run in the field would be of great help.

My bet is the guilty party is either Colonel Mustard with the double o-ring in the library, or Sam with the shotty amateur build in the garage.

 

Edited March 14, 2022 by Sarugo

[98Z5V]

What lower are you using?  I didn't see it mentioned above.  Something is wrong, if you bent the retainer pin  - that means the back of the BCG isn't pushing the buffer face off the retainer when you close the upper to the lower.  Let's solve that first.

Next, describe that XL gas system on the Odin 22" barrel - how long is the gas tube?  I can figure out the gas system length if you give me that info.

Oh, and always run an adjustable gas block wide open when you start.  That's the only way you're ever gonna find out if your gas port is large enough.

[Sarugo]

Thanks 98Z5B,

Lower is an 80% from righttobear.com.

Also of note, it’s the firing pin retaining pin that is bent. The buffer retaining pin looks fine… but it is leaving marks on the buffer face(shown in pic above) so I guess something is wrong. Any quick/easy fixes for this or is a new lower needed?

I believe the gas system is a rifle length +2, but I’m not positive. Odin Works sells the barrel, gas block and tube as a set. See photo below of inside of the receiver.

Thanks for the gas block advice, makes sense.

Sam

[edgecrusher]

Check the internal depth of you buffer tube. Also a picture of it showing the retaining pin minus the buffer and spring. Your gas tube is in the proper location in the cam cut out. Could you measure the gas port for us? Does your firing pin have a spring that goes on it? That bent pin in the picture isn’t a big concern for me

[DNP]

Is that pin another case of the hole being offset slightly out of position?  Who made the offset pin that would take care of that issue?  Seems like we’ve seen the chewed up buffers before with the gap between the carrier and buffer caused by the retaining pin hole location. 

[Armed Eye Doc]

1 hour ago, DNP said:

Who made the offset pin that would take care of that issue?

I don't know if this is the one that has been linked before.  But I found it through a search.  I believe @jtallen83has linked to one before.

https://gallowayprecision.com/offset-buffer-retainer-for-AR-15-rifles

[98Z5V]

^^^   That's the one, and it allows the buffer to be placed farther forward, so the BCG definitely pushed it off the pin, and it'll never chew up the buffer face again.  

5 hours ago, Sarugo said:

I believe the gas system is a rifle length +2, but I’m not positive.

Sounds about right.  I'll look up gas port sizes based on that.

EDIT - That ejector face looks pretty squared off.  That never helps feeding, specifically when the rounds are coming from the right side of the magazine.

Edited March 14, 2022 by 98Z5V

[Sarugo]

Hey all,

Appreciate the replies.

@edgecrusher the buffer tube is 7.75” internal depth. As you can see in the pic below the installation puts it a bit behind the lower receiver lip so functionally it’s actually closer to 7.875”. 
Some pics without the buffer/spring installed are linked below.
My calipers battery died, but as best I can tell gas port is roughly .094” diameter.
No spring on my firing pin.

 

@98Z5V do you have a photo of a correctly rounded ejector?

After removing the gas block I don’t think I’m leaking much gas. Also I had the block set up directly against the shoulder and after double checking the measurements(pardon the painters tape) that appears to be the correct location, no gap necessary here.

I’ve got a new extractor in the mail, I’ll get that offset buffer retaining pin and and lastly I’ll round off my ejector for the next range trip.

I plan in spending a full day at the range troubleshooting. Are there any useful tests I can do to help diagnose while I’m at the range?

[98Z5V]

37 minutes ago, Sarugo said:

do you have a photo of a correctly rounded ejector?

[98Z5V]

Squared off ejectors will fuk up every round feeding from the right side of the magazine - which is every other round...  When ejectors are jacked up, you notice it "intermittently" - until you start paying attention to it  - happening every other round, and those rounds are always coming from the right side of the mag...

Edited March 15, 2022 by 98Z5V

[Sarugo]

Thanks for the photos, I’ll round off my extractor corners a bit on the belt grinder.

 

Also, after measuring with better tools my gas port hole is actually somewhere between .078”-.08”, not .094”

[98Z5V]

15 hours ago, Sarugo said:

 

 

This receiver extension looks like it needs to go in another turn, but it's bottomed on the retaining pin.  You'd have to notch the bottom forward edge of the extension to clear the retaining pin.  

[mtrmn]

On 3/15/2022 at 1:54 PM, 98Z5V said:

This receiver extension looks like it needs to go in another turn, but it's bottomed on the retaining pin.  You'd have to notch the bottom forward edge of the extension to clear the retaining pin.  

Possibly true, but if the problem is the buffer contacting the retainer during operation the 2 available cures are in this thread: 

 

[mtrmn]

OK. I don't see a way to edit my post above, but after taking time to READ THE ENTIRE THREAD I realize most of the problem with the buffer/retainer contact has already been taken care of. My apologies for not doing my homework. However, a quick fix would be to cut the buffer face if you have access to the equipment or know someone who does.

[98Z5V]

9 hours ago, mtrmn said:

OK. I don't see a way to edit my post above, but after taking time to READ THE ENTIRE THREAD I realize most of the problem with the buffer/retainer contact has already been taken care of. My apologies for not doing my homework. However, a quick fix would be to cut the buffer face if you have access to the equipment or know someone who does.

That will work, but the entire face of the buffer needs an outer radius machined off.  Buffers rotate, so just one spot won't do it.   Depending on local machining costs for you, the better alternative might be that offset retainer pin.  Then, you can use any buffer you need to, without machining it.

[98Z5V]

20 hours ago, mtrmn said:

Possibly true, but if the problem is the buffer contacting the retainer during operation the 2 available cures are in this thread: 

Having a receiver extension that's not seated where it should be means that the back (internal) of the receiver is beyond the maximum internal depth.  That's when the ears on the BCG body start slamming the ears on the lower receiver, damaging your lower receiver.   Trying to avoid that right now, by fixing it now, so there's no damage to the lower, in the future. 

[Sarugo]

Thanks again everyone. Currently my rifle is mostly disassembled and I’m waiting on some new gas block screws(stripped ‘em) and a JP extractor. Once I receive those parts I plan to do the following…

- Install new extractor
- Remove one of the two O-rings from the extractor spring
- Notch the buffer tube and install it one more turn
- Remove the buffer retainer(if this works I will buy an offset one)
- Round off my ejector
- Open my gas block fully
- Switch from H3 buffer to an H2 buffer
- Clean my bore and chamber gently with a wire brush

I’ll then take it to the range for a day and report back.

Last two questions… when I drop a live round in the chamber and gently seat it with a finger it doesn’t fall out freely, I need to shake the rifle a bit(nothing crazy) and the round falls out of the chamber. Does this sound like a correctly sized chamber?

Also, with my bolt disassembled it closes easily on a live round. Does this mean My headspace is likely okay?

[98Z5V]

3 hours ago, Sarugo said:

Switch from H3 buffer to an H2 buffer

That's directly backwards.  Why are you doing this?

[Sarugo]

6 hours ago, 98Z5V said:

That's directly backwards.  Why are you doing this?

My thought was that since my bolt wouldn't lock back with the gas port fully opened that I may be slightly undergassed on account of a small gas port.

[Matt.Cross]

On 3/22/2022 at 7:54 AM, Sarugo said:

My thought was that since my bolt wouldn't lock back with the gas port fully opened that I may be slightly undergassed on account of a small gas port.

Running a lighter buffer won't really help that, it'll just create another issue to solve once your gas port issue is resolved. If your gas port is undersized, it's pretty easy to remedy.

[shooterrex]

If you are under gassed drill that puppy out. Don't compromise your recoil system to fix a problem with the gas system.

[Albroswift]

We did that 6.5 with an 18" BA barrel, wouldn't even budge with Armalite parts, got all the way down to an H buffer and a ar15 carbine spring before we got it to run. Like the barrel was designed for small frame recoil. Drilled it and put the right stuff in anyway. Just wasn't right. 

[98Z5V]

On 3/21/2022 at 3:32 PM, 98Z5V said:

Having a receiver extension that's not seated where it should be means that the back (internal) of the receiver is beyond the maximum internal depth.  That's when the ears on the BCG body start slamming the ears on the lower receiver, damaging your lower receiver.   Trying to avoid that right now, by fixing it now, so there's no damage to the lower, in the future. 

 

On 3/14/2022 at 8:45 PM, Sarugo said:

the buffer tube is 7.75” internal depth. As you can see in the pic below the installation puts it a bit behind the lower receiver lip so functionally it’s actually closer to 7.875”. 

^^^   This right here is exactly what I'm talking about.  It that receiver extension is truly 7 3/4" internal depth, it's out of spec.  It should be 7 5/8" internal depth.

What's an 1/8"?  0.125".  What's the thickness of a quarter? 0.069".  If that extension is truly 7 3/4" deep, then stick 2 quarters down the back of it before you put in the spring and buffer.  That's as close to "right" as you can make it, that way. 

[98Z5V]

Minimum on your gas port diameter, for the barrel config that you have, is gonna be 0.080".  Minimum.  Have you measured your gas port diameter yet?  If you have, and you've posted it, I missed it - had a pretty busy weekend last weekend, so my apologies in advance. 

This is the barrel that you have, and they - for some reason - do not state the gas block journal size in this page:

https://www.odinworks.com/6-5mm-Creedmoor-Barrel-p/b-6.5cm-22-2r-tg.htm

It is Rifle Gas +2", directly stated.  If I look on that page for their "upgrades" - they include a lo-pro gasblock, and that's listed at 0.750 diameter.  Please verify that your gas block journal size is 0.750". 

Edited March 23, 2022 by 98Z5V