Some issues with my last Ar build

[btnh6668]

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

Definitely didn't check mags with any gauges, i only know they worked with the same ammo on my other ar's. Typically what i do is i run my mags in batches after i buy new ones. All my USGI mags get new springs and anti tilt followers i number them and run them for functionality. I will definitely run the mag that didn't give me problems first and compare that to the other two. Won't hurt for me to bring different ammo as well.
As far as the ding goes mac it was not there the first time i took it out, because i inspected it when i had my issues the first time. That happened after this last trip. The indent matches perfect with the retainer.

 

[btnh6668]

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.

No sir 5oz rifle buffer and spring. Included in the UTG set.

 

[mac1911]

Definitely didn't check mags with any gauges, i only know they worked with the same ammo on my other ar's. Typically what i do is i run my mags in batches after i buy new ones. All my USGI mags get new springs and anti tilt followers i number them and run them for functionality. I will definitely run the mag that didn't give me problems first and compare that to the other two. Won't hurt for me to bring different ammo as well.
As far as the ding goes mac it was not there the first time i took it out, because i inspected it when i had my issues the first time. That happened after this last trip. The indent matches perfect with the retainer.
[/QUOTE\]

New springs dont make a mag good and function in one rifle does not always mean function in another.
For testing stick with that one known functioning mag and GI mags that you know function in other rifles.
The mag catch could be worn or defective, the mag catch notch on the mags could be a bit wonky.

The buffer dent? Since its only one dent I feel like face of the buffer has a High/low spot there and met a high/low spot on the bolt carrier ?

Hmmm gets me thinking whats harder the buffer or the detent/retainer.

Oh slowly with a good flash light make sure you Bolt Carrier is making slight contact with your buffer. Make sure your buffer tube is well seated and tight. As you close the upper down onto the lower watch for contact and the BC to push the buffer weight back.
Your BC should push the buffer back just enough to get it off the retainer.
Im not a fan of UTG except cheap scopes on cheap air rifles and 22s. Might want to try another lower.
Good thing is the BCG is a Brownells part , they will replace it 100% no BS.
Heck call them probably send you another over night

 

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

Stag = NO/GO

I can't tell you how many rifle courses I've seen your 1st pic in the OP with a Stag upper and their shitty feed ramps on some peoples rifles.

 

[btnh6668]

Stag = NO/GO

I can't tell you how many rifle courses I've seen your 1st pic in the OP with a Stag upper and their shitty feed ramps on some peoples rifles.

Interesting. I was not even thinking that direction. Ill have to pay closer attention to that area.

 

[mac1911]

Stag = NO/GO

I can't tell you how many rifle courses I've seen your 1st pic in the OP with a Stag upper and their shitty feed ramps on some peoples rifles.

so whats happening is the bullet tip or edge of neck snagging cause the bolt to jump over the cartridge?
Have my share of stag products. I beat the sknot out of my first one. All steel cheap ammo.

Either way time to diag , not change parts.
By the looks of OPs picture it seams that the cartridge just barely was caught by the bolt dislodging it some?
Mag not seated , waek/binding spring/follower. Bent feed lips?
Its all good, keep looking

Might as well toss my thoughts on lube in.
A in spec AR will run bone dry. Ideal no. For long periods of time , not so much. A properly lubed AR will run fine and for me thats far from what people call "wet"

 

[teamRR]

I think Stag is good to go, on the better end as far as mil spec ARs.

Can't see how this is a feed ramp problem given the 1st pic where basically the bolt caught a cartridge in the middle. The problem began before the round touched a feed ramp.

 

[mac1911]

I think Stag is good to go, on the better end as far as mil spec ARs.

Can't see how this is a feed ramp problem given the 1st pic where basically the bolt caught a cartridge in the middle. The problem began before the round touched a feed ramp.

Every manufacture has their problems, some more than others some more serious.
If it was made to spec there should be no issues. Its a matter of IF every part is checked before shipping.

 

[teamRR]

Every manufacture has their problems, some more than others some more serious.
If it was made to spec there should be no issues. Its a matter of IF every part is checked before shipping.

Yes definitely agree. Just maybe its not saying much but if someone said, Ruger, S&W, PSA, or Stag, all basic carbines, I would take the Stag from my experience and could provide some reasoning.

If you threw Colt in there I would take the Colt but I couldn't really specify what makes it better other other than the name makes it worth more.

 

[John380]

Check that the hammer spring is in correctly. Symptom was the same as I had on a build where I put it in backwards. Easy mistake to make, hard to catch visually.

 

[Fixxah]

First problem is naming the firearm. Not sure after that.

 

[akma]

AR's can be finicky with a conglomeration of different manufactured parts, stacking of tolerances along with all the other fine points brought forth. Anyone of them by themselves or in combination. That leaves a ton of potential possibilities.

How does the BCG slide by itself and what kind of force does it take to close by hand? Remove the firing pin and feed rounds. See if it's dragging or gritty. Possibly everything is a little tight and needs some wearing in.

I've dealt with this and it's not fun till it's running the way it should. Just because something worked in another gun doesn't guarantee it will work in that one.

Yes YouTube is your friend.

All the best.

 

[mac1911]

Check that the hammer spring is in correctly. Symptom was the same as I had on a build where I put it in backwards. Easy mistake to make, hard to catch visually.

Interesting hammer sprin in backwards caused random miss feeds?

 

[fshalor]

No sir 5oz rifle buffer and spring. Included in the UTG set.

I'm only asking. Because this happened to me. Did you actually measure it?

My second AR was a 20" green mountain barrel rifle build. I ordered a rifle buffer and spring.

I received a mid length spring and rifle buffer.

As long as the spring and buffer are balanced, things seem to work. Match them up wrong, or not get the gas lock dead on when you pin it and weird things can happen.

 

[John380]

Interesting hammer sprin in backwards caused random miss feeds?

Yes, and it causes the trigger pin to walk as well. And some failure to fire from light strikes.

 

[btnh6668]

Ill have a range report on monday. Thanks for all the suggestions.

 

[mac1911]

Yes, and it causes the trigger pin to walk as well. And some failure to fire from light strikes.

The light strikes I can see but miss feeds, that seems odd? Although a part not installed correctly can have cascading effects.

 

[John380]

The light strikes I can see but miss feeds, that seems odd? Although a part not installed correctly can have cascading effects.

Thanks for following up Mac. I went to the range yesterday (hammer spring oriented correctly) and everything functioned well, except:
Dropping the bolt catch, the first round from a full magazine didn’t strip off and feed. Changed mags and had no other issue.

I tried it just now by only manually cycling the charging handle ( not firing) through the first 10 rounds and not every round is stripping/feeding.

So my failure to feed wasn’t related to the hammer spring installed backwards. Next step is to see if it’s localized to one or more magazines. Maybe I’ll even clean it.

 

[teamRR]

Thanks for following up Mac. I went to the range yesterday (hammer spring oriented correctly) and everything functioned well, except:
Dropping the bolt catch, the first round from a full magazine didn’t strip off and feed. Changed mags and had no other issue.

I tried it just now by only manually cycling the charging handle ( not firing) through the first 10 rounds and not every round is stripping/feeding.

So my failure to feed wasn’t related to the hammer spring installed backwards. Next step is to see if it’s localized to one or more magazines. Maybe I’ll even clean it.

Just an FYI, manual feed tests are a little tricky - useful but if you don't let the bolt freewheel and slam shut sometimes you witness out of battery, a failure to eject, or even a botched feed that never happens in normal operation.

It is tempting to kinda slowly release the charging handle and kinda unnatural to rip it again and again.

 

[mac1911]

Thanks for following up Mac. I went to the range yesterday (hammer spring oriented correctly) and everything functioned well, except:
Dropping the bolt catch, the first round from a full magazine didn’t strip off and feed. Changed mags and had no other issue.

I tried it just now by only manually cycling the charging handle ( not firing) through the first 10 rounds and not every round is stripping/feeding.

So my failure to feed wasn’t related to the hammer spring installed backwards. Next step is to see if it’s localized to one or more magazines. Maybe I’ll even clean it.

All though my statement about “its always the mags” was sort of a joke . If you look at the symptom/diag chart the mags have alot of failure symptoms.
Like doing alignments no sense if tou dont make sure the tires have correct pressure and nothing is worn.

 

[Uzi2]

If your gun won't strip a round and chamber it fully into battery by pressing the bolt release, it sounds like your buffer spring is weak.
It should be able to do this with a full 30rd magazine......every time.

• Standard Carbine Spring – Measures 10.5” with 37 to 39 coils
• Standard Rifle Spring – Measures 12.75” with 41 to 42 coils

From:
TECHNICAL MANUAL
ARMY NO. 9-1005-319-23&P
AIR FORCE TO 11W3-5-5-42

RIFLE: 11 3/4 Inches (29 85 cm)
minimum to 13 1./2 inches (34 29 cm)
maximum

CARBINE: 10 1/16 inches (25.56 cm)
minimum to 11 1/4 inches (28.58 cm)
maximum.

 

[mac1911]

If your gun won't strip a round and chamber it fully into battery by pressing the bolt release, it sounds like your buffer spring is weak.
It should be able to do this with a full 30rd magazine......every time.

• Standard Carbine Spring – Measures 10.5” with 37 to 39 coils
• Standard Rifle Spring – Measures 12.75” with 41 to 42 coils

From:
TECHNICAL MANUAL
ARMY NO. 9-1005-319-23&P
AIR FORCE TO 11W3-5-5-42

RIFLE: 11 3/4 Inches (29 85 cm)
minimum to 13 1./2 inches (34 29 cm)
maximum

CARBINE: 10 1/16 inches (25.56 cm)
minimum to 11 1/4 inches (28.58 cm)
maximum.

the problem I see is the bolt is jumping over the cartridge after an initial engagement of the bolt to the case head ?
What I see is the case not releasing from mag , or a release angle is to steep causing it to hit the top of the barrel?
OP did not show if the rounds jamming are getting damaged

View: https://youtu.be/phwDMrau_7Y

 

[akma]

@mac1911 great video. Would that then be a mag or mag alignment problem?

 

[50wt]

2400fps match ammo and even 2800fps reloads didnt cycle in this rifle length setup. Long story short, at some point long ago, the weights in the buffer were pulled and replaced with a much heavier, carbide endmill , which was clearly too heavy.

 

[mac1911]

@mac1911 great video. Would that then be a mag or mag alignment problem?

Yes

could be both , I like that vid as it shows pretty well what that case is doing when cycling.
OPs picture just makes me thing the bolt was/is struggling to strip the case out of the mag from the start?
O well im sure OP will figure it out

 

[mac1911]

2400fps match ammo and even 2800fps reloads didnt cycle in this rifle length setup. Long story short, at some point long ago, the weights in the buffer were pulled and replaced with a much heavier, carbide endmill , which was clearly too heavy.

Guy was running hot 80/90 grain loads!
thats F’n awesome

Your velocities are a bit low for average 5.56 but that does not mean much really.
My Stock mil spec A2 will run on some “low” velocities with cast bullets.
I also run some pretty hot 77s once in a while.
Its all fun until shit dont work!

 

[fshalor]

If your gun won't strip a round and chamber it fully into battery by pressing the bolt release, it sounds like your buffer spring is weak.
It should be able to do this with a full 30rd magazine......every time.

• Standard Carbine Spring – Measures 10.5” with 37 to 39 coils
• Standard Rifle Spring – Measures 12.75” with 41 to 42 coils

From:
TECHNICAL MANUAL
ARMY NO. 9-1005-319-23&P
AIR FORCE TO 11W3-5-5-42

RIFLE: 11 3/4 Inches (29 85 cm)
minimum to 13 1./2 inches (34 29 cm)
maximum

CARBINE: 10 1/16 inches (25.56 cm)
minimum to 11 1/4 inches (28.58 cm)
maximum.

Can't like this enough.

This data was my issue. I bought a spring. Package said it was the right spring. I installed it and it didn't strip feed right.

Comparing to this data, the spring in the sealed blister pac was NOT right for the application.

 

[50wt]

Guy was running hot 80/90 grain loads!
thats F’n awesome

Your velocities are a bit low for average 5.56 but that does not mean much really.
My Stock mil spec A2 will run on some “low” velocities with cast bullets.
I also run some pretty hot 77s once in a while.
Its all fun until shit dont work!

the slow stuff was 77 gr match and the reloads were berrys 55 with 23.5gr of h335. The hodge podge carbine runs flawlessly with the reloads.

I like that video too
.

 

[mac1911]

the slow stuff was 77 gr match and the reloads were berrys 55 with 23.5gr of h335. The hodge podge carbine runs flawlessly with the reloads.

I like that video too
.

Dude punch those 77s a little harder.!
What manufacture has 77s at 2400fps?
Seems slow for a commercial manufacture ?

 

[50wt]

I think it's PMC match stuff that I picked up from *edit typo" DW619" in NH a couple weeks back.