LR-308 build won't cycle. Please help so I don't have to pay my gunsmith any more money.

[Mrj209]

Hey guys, new to the discussion board, but have been reading posts trying to get a handle on what is going on with my new build.

First 308 size build, my AR-15s run well so I though I could figure this out on my own. No luck yet.

I have a live free upper and lower matched set, 20in ballistic advantage barrel with a rifle length gas system, M5 carbine buffer system and Nickel Boron BCG. 

Waterboarding info:

Aero M5 carbine buffer system. 3.8 oz buffer that is 2.57 in long.

Internal buffer tube length is right at 7in.

Aero M5 carbine Spring is 11.25in long and has 26 coils.

Rifle length gas tube is 15 and 1/8th in long.

Gas port is .086in and the shoulder is .750. Odin works adjustable gas block.

Problem: fires and ejects, but won't lock open or pick up another round. Bolt locks back manually. Tried every setting on the gas block with no success. I ran out very well oiled so there is some of that in the pictures. Please help!

 

 

 

Edited July 23, 2021 by Mrj209

[edgecrusher]

Recoil system bro. Looks like you’ve read some posts, thank you, it’ll help this go much faster. Buffer is too light, needs to be over 5 oz, either 5.3 or 5.6. Spring is also junk. Should be 13.75”. 
 

If it’s available you can get the whole Armalite system and be done. Or…. Shop for a sprinco orange and a kak buffer. Your gas tube is good. Gas port is a little on the small side but glaring issues first

[shooterrex]

This should fix your problem. If the web shows out of stock call them.

https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories/Lower-Receiver-Parts&Category=ac614400-ff09-4cdf-9d35-419a654e7201

[Mrj209]

26 minutes ago, shooterrex said:

This should fix your problem. If the web shows out of stock call them.

https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories/Lower-Receiver-Parts&Category=ac614400-ff09-4cdf-9d35-419a654e7201

They are out of stock, and I called. Said they might be out of stock for a while.

I'm wondering if you guys could explain why a heavier buffer system would fix this.

It's behaving like an undergassed gun. Never able to lock back, but a perfect 3 - 4  o'clock ejection. Why would a heavier buffer and stronger spring help that?

No disrespect, just honestly trying to learn. 

Also, what specifically would you recommend in place of the Armalite system?

[RacerX]

At what length do you switch from carbine-length buffer parts to rifle-length parts?

[DNP]

16 minutes ago, RacerX said:

At what length do you switch from carbine-length buffer parts to rifle-length parts?

When you have a rifle length buffer tube.  You can run either system with any gas system. Just depends on wether you’re running collapsible stock or a rifle stock. Weights are about the same, spring and buffer lengths are different. 
 

@Mrj209 how lubed up are you?  Get that thing dripping wet. Replace that buffer system first. Then get a few boxes through it. 

[Mrj209]

@DNP I ran it way wetter than I normally would have because the cerakote was making it a little gummy when I first got it. Spitting lube the whole last range session. 

Cerakote has worn off and the bolt moves smoothly btw.

So it seems there is a consensus on me needing a heavier buffer.

Planning on ordering this with the spring they sell as well, good choice?

 

[edgecrusher]

28 minutes ago, Mrj209 said:

They are out of stock, and I called. Said they might be out of stock for a while.

I'm wondering if you guys could explain why a heavier buffer system would fix this.

It's behaving like an undergassed gun. Never able to lock back, but a perfect 3 - 4  o'clock ejection. Why would a heavier buffer and stronger spring help that?

No disrespect, just honestly trying to learn. 

Also, what specifically would you recommend in place of the Armalite system?

1. I already listed alternate parts

2. your bolt carrier group isn’t under gassed, it’s under assed. It’s not slowing the reciprocating mass down enough. Ejection don’t mean shit if it won’t function.

[Mrj209]

11 minutes ago, edgecrusher said:

1. I already listed alternate parts

2. your bolt carrier group isn’t under gassed, it’s under assed. It’s not slowing the reciprocating mass down enough. Ejection don’t mean poop if it won’t function.

@edgecrusher Sir, I already said that I mean no disrespect and am honestly trying to learn. 

[Mrj209]

@DNP what buffer/spring combo would you recommend other than the Armalite system?

[edgecrusher]

I don’t feel disrespected, lot thicker skin than that. I posted the why so you could learn. 

[edgecrusher]

The kak buffer and orange spring orange spring will work.

[RacerX]

40 minutes ago, DNP said:

When you have a rifle length buffer tube.  You can run either system with any gas system.

 

But isn't @Mrj209 running all carbine length/weight parts, including the buffer tube?

 

Aero M5 carbine buffer system. 3.8 oz buffer that is 2.57 in long.
Internal buffer tube length is right at 7in.
Aero M5 carbine Spring is 11.25in long and has 26 coils.

 

[DNP]

1 hour ago, RacerX said:

At what length do you switch from carbine-length buffer parts to rifle-length parts?

 

11 minutes ago, RacerX said:

 

But isn't @Mrj209 running all carbine length/weight parts, including the buffer tube?

 

Aero M5 carbine buffer system. 3.8 oz buffer that is 2.57 in long.
Internal buffer tube length is right at 7in.
Aero M5 carbine Spring is 11.25in long and has 26 coils.

 

I quoted both of your posts for reference. Your question was at what length do you switch from carbine to rifle. Rifle buffer goes in rifle tube on rifle stock. Carbine buffers go in carbine tubes…with the only issue being there are different length tubes and different length buffers with the problem amplified by different length springs. 
 

the lighter weight buffers have been created by companies “shaving weight” and cost on their end. It doesn’t work as reliably with all the mixed bag of parts out there. They then had rifles that seemed over gassed, so they drilled the ports smaller in hopes of cutting that back. Stick with the basics and get it functioning reliably, then change parts one at a time if you have the desire to do something more with it. 
 

The armalite kit is mostly recommended because it’s undeniably proven. It works. Many others work too, but this is a known batch of parts that can be ordered together and it will function. The KAK and Sprinco Orange recommended by edge will work well also. There may be many others. There are a lot of great threads debating the buffer set ups. The one thing that always comes back as “problem solved” is that armalite kit. 

Edited July 23, 2021 by DNP
Fat thumbs

[Mrj209]

@DNP unfortunately Armalite is sold out and I can't find that system anywhere else. I will check out some of the other posts to see if there is anything that has a similar success rate. Thanks for your post it was descriptive and helps me move in the right direction. 

[shooterrex]

The KAK buffer in the 5 1/2 oz range w/the springco orange spring will probably work in your buffer tube. The Armalite set up is just a bit longer on length. That's why the buffer is a bit longer.

Doesn't matter which stock set up you run as long as the the springs and buffer weights are correct to offset the BCG mass and amount of gas pushing the BCG rearward.

[Mrj209]

@shooterrex I ordered the kak buffer in this picture along with the kak heavy spring. I'm also going to order the springco orange spring. Thank you for your advice.

[Mrj209]

@RacerX You choose your barrel and that determines your had tube length.

Then you devine what kind of stock you want and that determines whether you're going to use rifle or carbine components. 

You can mix and match carbine and mid length gas systems with rifle buffer systems and vice versa. 

[shooterrex]

40 minutes ago, Mrj209 said:

@shooterrex I ordered the kak buffer in this picture along with the kak heavy spring. I'm also going to order the springco orange spring. Thank you for your advice.

That one should work w/the proper spring.

[98Z5V]

These guys pretty well covered it.  That recoil system in your gun is fucked - it'll never work.  Only thing I would change is bump that gas port diameter up to 0.090". 

When you test this gun, ALWAYS test it with your adjustable gas block WIDE OPEN.  As open as it will go.  You waste less ammo that way.

Since it's all about learning, or the desire to learn, here in this thread, then read this:

 

Edited July 24, 2021 by 98Z5V

[Mrj209]

@98Z5V thank you for that link, that was some good reading. Lots of stuff is starting to make sense now.

I have a new recoil system on the way, hopefully it's up to snuff. 

If I wanted to increase my gas port dia, what tools would I need? Not just a hand drill I assume...

[jtallen83]

10 minutes ago, Mrj209 said:

Not just a hand drill I assume...

A hand drill works fine, just let the bit do the work, put a dowel in the bore just in case.

[Mrj209]

The heavy buffer and springco orange spring didn't help. Still won't lock back.

[DNP]

I didn’t re-read the whole thread. What mags and how many rounds through it?

[98Z5V]

He started a new one - gas port is too small.