Some issues with my last Ar build

[btnh6668]

UPDATE on post #61

I am not an AR noob but i am also far from an expert. So there are two main issues i am having with my last build. I took her out the first time two weeks ago in the rain to just try her out and had a out 7 failures to feed out of 50 rounds. So i take her out again today to get it sighted in. Out of 87 rounds (i load all my 30rd with 29) i had 5 times where it failed to pick up the next round and had another 7 or 8 failures to feed correctly. Im shooting Malaysian 556 which ive already shot 2600 through my other ar's flawlessly. It happened in 2 out of my 3 mags. The last mag ran flawless. The mags look fine, everything internally looks fine. Its a brownells bcg which i have never used before. I always use bcm but they were out of stock for a while and settled with the brownells. Any ideas?

 

[Artie]

For troubleshooting, throw one of your other uppers on the lower and see if it happens. If it still does, maybe buffer or buffer spring. If not,, throw the upper on one of your other lowers. Also, try another bcg and see if that changes things if concerned with it being a Brownells. Good luck

 

[caligula]

I second trying another BCG. I take it you have used these mags before with no issue?

 

[btnh6668]

I second trying another BCG. I take it you have used these mags before with no issue?

That is correct. Mags worked fine in other ar's. I am going through the rifle now and noticed a divot on the buffer from the retainer which i have never seen in my other lowers.

 

[SKumar]

Trying changing the buffer weight or the buffer spring. That makes a miraculous difference with troubleshooting ARs.

 

[btnh6668]

Trying changing the buffer weight or the buffer spring. That makes a miraculous difference with troubleshooting ARs.

Think i am leaning in that direction. Any preference for a 20" upper?

 

[SKumar]

Think i am leaning in that direction. Any preference for a 20" upper?

I’m not an AR expert, but it looks like the bolt is closing before it’s behind a round. It could be that the BCG is coming in too fast (common with mil spec buffer), or the magazine is not pushing rounds up hard enough.

 

[teamRR]

Possibilities:

1 - bcg not coming back far enough: common reason insufficient gas, too much buffer or spring, something hanging it up. In this realm a strong possibility for gas block not aligned.

2 - mag not sitting right or feeding right, less likely than the above

3 - over gassed and bcg is bouncing hard off the fully compressed buffer and spring, less likely than all, but would be too light buffer/spring or too much gas. I really doubt it as usually this symptom is very intermittent and is mixed with ejected cases bouncing back in off the deflector, hard to accomplish something that is over gassed with such frequency of problems - usually over gassed is a 2% sort of problem.

What is the direction of the ejecting cases? If they are coming out kinda weak and behind you its undergassed.

 

[Marty McFly]

I vote lighter buffer. Dent in buffer looks like it is fighting the weight of your buffer.

 

[btnh6668]

Possibilities:

1 - bcg not coming back far enough: common reason insufficient gas, too much buffer or spring, something hanging it up. In this realm a strong possibility for gas block not aligned.

2 - mag not sitting right or feeding right, less likely than the above

3 - over gassed and bcg is bouncing hard off the fully compressed buffer and spring, less likely than all, but would be too light buffer/spring or too much gas. I really doubt it as usually this symptom is very intermittent and is mixed with ejected cases bouncing back in off the deflector, hard to accomplish something that is over gassed with such frequency of problems - usually over gassed is a 2% sort of problem.

What is the direction of the ejecting cases? If they are coming out kinda weak and behind you its undergassed.

4 o'clock

 

[drgrant]

What is the upper made out of where did it come from? Who made it? What kind of gas system? etc.

The brownells carriers are usually pretty good, so I doubt its that by itself.

 

[teamRR]

Between 3 and 4 o'clock

Hmmm - we may all be wrong here. 3 or 4 o'clock is perfect, however that "funny feed issue" where it grabs the middle of the cartridge has been classic lack of gas in my experience.

If it were mine I would start by checking gas block alignment, all you really gotta do is plug the barrel off with a rubber plug in the chamber area, wrap a little electrical tape around the flash hider, and blow through it with your mouth. Compare a good working upper to the bad working one, if the gas block is set far wrong you will notice the difference in resistance.

 

[PATRON]

Just for the hell of it try some different ammo.

 

[btnh6668]

What is the upper made out of where did it come from? Who made it? What kind of gas system? etc.

The brownells carriers are usually pretty good, so I doubt its that by itself.

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Right ejection model. With a VG6 muzzle brake i have used in my other 20" and 16"

 

[Uzi2]

First of all, you are running your rifle way too dry, especially for a new build, the rifle it should be WET with lube....dripping wet.

Second, The dimple on your buffer means nothing

How about some specs?

Barrel length?

Gas tube? Carbine or rifle length?

What type of stock, A1 or A2? If its an A1 or A2, you need a rifle buffer and rifle spring.

Find "School of The American Rifle" on youtube and watch his videos.


View: https://youtu.be/DTpWfjVFfEU

 

[Marty McFly]

What is the upper made out of where did it come from? Who made it? What kind of gas system? etc.

The brownells carriers are usually pretty good, so I doubt its that by itself.

Highpoint upper

 

[71montess]

Rifle or Carbine buffer and spring to match.

 

[Marty McFly]

Rifle or Carbine buffer and spring to match.

I vote carbine under the circumstances

 

[btnh6668]

First of all, you are running your rifle way too dry, especially for a new build, the rifle it should be WET with lube....dripping wet.

Second, The dimple on your buffer means nothing

How about some specs?

Barrel length?

Gas tube? Carbine or rifle length?

What type of stock, A1 or A2? If its an A1 or A2, you need a rifle buffer and rifle spring.

Uzi the pics are deceiving. Not dry by a long shot, i started to wipe off parts to look for any abnormalities. She was lubed well. I keep my girls wet. The stock is a UTG A2 set. I used it on my other 20" with great results. The kit includes a rifle length spring and buffer. I posted a link above with all the specs of the upper.

 

[Uzi2]

Uzi the pics are deceiving. Not dry by a long shot, i started to wipe off parts to look for any abnormalities. She was lubed well. I keep my girls wet. The stock is a UTG A2 set. I used it on my other 20" with great results. The kit includes a rifle length spring and buffer. I posted a link above with all the specs of the upper.

Ok on the lube and the UTG A2 kits, I've used several without issue.

 

[greencobra]

Dent in buffer looks like it is fighting the weight of your buffer.

that buffer rotated in there, that divot is from the retaining pin. i'd say the buffer and spring are working faster than is needed, misfeeding the rounds coming out of the mag. just my speculation.

 

[Marty McFly]

that buffer rotated in there, that divot is from the retaining pin. i'd say the buffer and spring are working faster than is needed, misfeeding the rounds coming out of the mag. just my speculation.

Yeah but the dent shows a heavy buffer hitting the pin. In my opinion of course

 

[greencobra]

Yeah but the dent shows a heavy buffer hitting the pin.

or just a light buffer and spring pounding the crap out of the gun. a heavy buffer would slow the action down, allowing for proper feeding of the rounds from the mag. but hey, that's what gunsmiths are for, to figure this stuff out.

 

[Marty McFly]

or just a light buffer and spring pounding the crap out of the gun. a heavy buffer would slow the action down, allowing for proper feeding of the rounds from the mag. but hey, that's what gunsmiths are for, to figure this stuff out.

True. Its either to heavy or too light. Lol

 

[snax]

Do your ramps line up with the ones in your barrel extension?
Do your failures come from feeding from both sides of the mag?
The bolt doesn't have any marks it looks, but check your extenstion.
That pin could be off 1/64 and cause issue.
You can gently dremel them to match, but if the barrel is off, I'd send it back.

 

[mac1911]

its the f***ing mags its always the f***ing mags!

Failure to Feed	1 - Magazine catch spring weak or broken	Replace magazine catch spring
2 - Magazine catch defective	Replace magazine catch
3 - Magazine catch out of adjustment	Adjust magazine catch to capture magazine
4 - Magazine catch notch defective	Replace magazine
5 - Magazine lips burred or broken	Replace magazine
6 - Magazine follower defective, or binds during operation.	Replace magazine
7 - Magazine spring weak or broken	Replace magazine
8 - Magazine tube dented	Replace magazine
9 - Short recoil	See short recoil below

 

[btnh6668]

Dgrant and Green you guys are too much. Mac all my mags are numbered so i know for a fact those mags work in my other ar's. According to UTG the buffer that is included is 5oz. Should i try heavier or lighter?

 

[mac1911]

Dgrant and Green you guys are too much. Mac all my mags are numbered so i know for a fact those mags work in my other ar's. According to UTG the buffer that is included is 5oz. Should i try heavier or lighter?

Your words "2 out of 3 mags, last mag ran flawlessly"
Unless your checking your mags with gauges you dont know if those other mags are good.

Allso no idea if your mag catch is seating the mags correctly. i would run another round of testing with that 1 mag that ran flawlessly....

That little ding in your buffer? Looks more like the finish got damaged. UTG ?
I tend not to mess with buffers/springs as long as they are in spec.
I have run my carbine upper on my A2 lower and my A2 upper on my M4 lower. Maybe not ideal but functions

 

[mac1911]

That is correct. Mags worked fine in other ar's. I am going through the rifle now and noticed a divot on the buffer from the retainer which i have never seen in my other lowers.

One little spot does not really compute as a problem for me. Heck that could have been there from the factory. i would suspect more damage if somehow the buffer was beating itself to death.
I would inspect the rear of the BCG for anything that might be making marks. Long shot is BC might be a little short ?
Whats the chances of the buffer face not being square/flat and that dent is a high/low spot?
Again I would expect to see more signs of multiple impacts if buffer face to Bolt Carrier buff detent interface issues.?

 

[fshalor]

I’m not an AR expert, but it looks like the bolt is closing before it’s behind a round. It could be that the BCG is coming in too fast (common with mil spec buffer), or the magazine is not pushing rounds up hard enough.

Sounds like
Under gassed.
Over sprung.

20" barrel means you should be in rifle bits out back. I'm betting you have carbine or mid buffer And spring.