AR-15 build will not cycle. Need help/advice

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mookiie

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Hey guys,
I built an AR-15 with a rifle length gas system and a luthar adjustable stock with a rifle buffer. This has a 20 inch SS fluted barrel chambered in .223 wylde. I cannot get this rifle to cycle and I am asking for your help please!

To catch you up:
I have never been able to get this gun to chamber a second round, almost positive it is short stroking. I checked to ensure the gas block was installed correctly. I then replaced it with a adjustable gas block.
Today at the range I adjusted the port from all the way up to all the way down to the point it was no longer ejecting spent cases....
I am out of ideas at this point?
My next theory is to try using a carbine/lighter buffer than the full size rifle one currently installed? Anyone have any other ideas.
 
I did not drill the barrel hole. I assume it would be standard size for rifle length gas system?
 
Do you know the hole size it should be? 1:8 twist and rifle length gas system - if that info helps.
I will tear it down and check it out tomorrow to ensure it is clear and the diameter. Update you when I get it tore down.
 
Before tearing anything down, do a lock back check.

Verify that the mag to be used will lock back check will engage the bolt hold open.

Place a single round in the magazine, then load the rifle.

Fire the rifle and check to see if the BCG locks back.

Use full power 5.56 ammo.

If it doesn't lock back you have short stroking. start looking for leaks, blockages and mis-alignments. If it does lock back, your problem lays elsewhere.
 
Insure the gas key is secure to the carrier, and staked in place. Check your gas rings too- are they tight in the carrier? Are you trying different magazines?
 
If it won't feed a second round, will it lock back on an empty mag?

If you feed in ONE round, drop the mag, and hold your support thumb on the tail of the bolt catch, will it lock back?

Does it fail to feed with all magazines? All types of ammo? Mag drag on the BCG is the most common cause for short stroking. Low power ammo right behind it.

Does the bolt lock back if you insert an empty mag and pull the charging handle fully to the rear? How far does the bolt nose clear the bolt catch when holding the charging handle fully to the rear?

Assuming your Luth-AR is a rifle extension, do you have the vented stock screw in place retaining the stock?

Are the gas rings good in the rifle? Will the rings support the BCG without collapsing if stood on the bolt?

Are there any carbon witness marks revealing gas leaks around the gas block, gas tube, or gas key? Is the gas key tight?

Gas alignment is pretty simple for me - open your AGB fully, stick a fired case in the chamber and blow into the muzzle, you can feel when the block is properly aligned over the gas port. If your journal shoulder is cut for a clamshell handguard, but your AGB not meant for the front retainer ring, you'll need to space the AGB off of the shoulder accordingly. Blowing through the gas system and sliding the gas block around on the barrel will let you find the sweet spot with ease. You'll feel leaks here typically too.
 
First things first. Remove the upper and then remove the BCG. Check the gas key to make sure it is properly mounted, staked, and secured. If that checks out OK, drop a dummy round into the chamber, and hold it there with your finger. Blow on the muzzle. Is air moving? There will be resistance because you should be blowing through a small hole, but there should be air moving. If not, your clogged up, pull gas block and figure out of its a clogged block, a clogged tube, or misaligned gas system. After a few shots there should be enough of a carbon ring on the barrel to show you how the block is lining up.

Secondarily... do you have another upper and/or another lower? You could swap lowers and verify that the problem stays with the upper. If the problem goes away on the other lower then you have a lower issue. I have heard of springs being too strong, and I have heard of buffer weights being off. I would be very skeptical of fiddling with those without trying other stuff first because if you increase the BCG speed you can easily start damaging things. On an adjustable gas system you could compensate by reducing gas flow though.
 
Since it sounds like you've fired it a good number of times can you see anywhere that gas is escaping from such as the base of the gas key or from the gas block?

Have you tried a different ammo?

If everything in the gas system and ammo is sound your two options are to drill the gas port bigger, or reduce the buffer and spring. You can take the buffer apart and replace weights with short pieces of rubber hose, and you can cut length off the spring. You cannot use a carbine buffer in a rifle tube. The "correct" way would be to fix the gas system, but there is more than one way to skin a cat.
 
mookiie said:
I built an AR-15 with a rifle length gas system and a luthar adjustable stock with a rifle buffer
Click to expand...

I ask just for clarity, are you using LuthAR’s adjustable rifle stock on a rifle length extension or a carbine stock and extension? If the latter, you’ll want a standard carbine buffer and spring or better yet an A5. Pictures would help.
 
Whose the barrel maker? Would be curious to see what gas port size they put on their barrels. A preemptive email to them while you are performing the steps that @MistWolf stated would be prudent to find out the details.

Since it seems you've fired it quite a few times check the gas key for carbon/soot flashing which will be an indicator of a loose gas key.
 
I had what sounds like the same problem a year ago or so. I pulled my barrel specs and THR members noted that the gas port hole was undersized. I used a small drill bit and carefully and ever so slightly enlarged the hole. After doing so, my AR has cycled perfectly and hasn’t had a hiccup. You can play with buffers, spring lengths, etc, but if you have a good gas block, a good BCG and it’s not cycling back far enough to reliably cycle and lock open on the last round, then I’d look at opening the gas port.
 
All thanks for the advice.

I have not been able to test lock back after firing more the block and blow technique yet.

But here is the barrel used:
https://www.midwayusa.com/product/7...-_-productslike-_-productslike-_-producttitle



This AR-STONER™ AR-15 Barrel is perfect for use in competition where both accuracy and reliable functioning are very important factors to a successful match. The barrel uses the popular and versatile 223 Wylde chamber, which has a longer throat than the SAAMI spec for 223 Remington to allow for the safe usage of 5.56x45mm NATO ammunition and enhanced reliability. However, accuracy potential is also greater than a 5.56 NATO chamber due to slightly tighter tolerances, making the 223 Wylde an ideal compromise that retains the benefits of both of the other two chamber options.

This Medium Contour Barrel is manufactured from 416R Stainless Steel and uses 5R Rifling with a 1 in 8" Twist. It is fluted along its length for greater stiffness, faster cooling and reduced weight. Additional features include a Mid Length Gas Port, M4 Feed Ramps and 1/2"-28 threaded muzzle. Barrel extension and locator pin are both included and installed at the factory.



I just saw this review on the item:

"Had to drill out the port to .078
After reading other reviews for this product (thanks reviewers) I knew I might have to drill out the gas port. I tried it in its stock form and it was short stroking. Drilled the port out with a 5/64 bit and it's been flawless since. It's putting together sub moa groups at 50 yards with the bushnell trs-25 3moa red dot. Used the ar stoner low pro gas block and the APF NiB bolt carrier group. Zero gas leakage at the block. Barrel is dimpled for easy, accurate and secure block placement. You want to pay three times as much for a cool brand name that you can brag about in a forum? Cool. Just don't give your wife grief anymore when she spends a small fortune on a bag that has the letters MK all over it."

Using a full size spring/buffer. Will post pictures. Have not checked the gas port hole size but that seems to be my next best option.
 

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mookiie said:
Hey guys,
I built an AR-15 with a rifle length gas system and a luthar adjustable stock with a rifle buffer. This has a 20 inch SS fluted barrel chambered in .223 wylde. I cannot get this rifle to cycle and I am asking for your help please!

To catch you up:
I have never been able to get this gun to chamber a second round, almost positive it is short stroking. I checked to ensure the gas block was installed correctly. I then replaced it with a adjustable gas block.
Today at the range I adjusted the port from all the way up to all the way down to the point it was no longer ejecting spent cases....
I am out of ideas at this point?
My next theory is to try using a carbine/lighter buffer than the full size rifle one currently installed? Anyone have any other ideas.
Click to expand...

You said a rifle buffer. A rifle buffer will not work in a collapsible stock. It's too long which would explain why your rifle is not cycling

kwg
 
That is the LuthAR adjustable (not collapsible) rifle stock on a rifle extension so the buffer/spring combo should be fine.

Take care with drilling, buy a good bit, and go slow (preferably with a drill press and oil).
 
You can usually get by with using a lighter buffer on a mildly under gassed rifle. Remove a weight from your buffer. Its a lot easier to try rather than drilling holes in your barrel.
 
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