Greetings,
Recently, finished putting together a 10in 7.62x39 AR15. Everything seems to be fine until I try to load a round.  It will go into full battery with or without a round. However, when I chamber a round but try to clear it, the BCG gets stuck.  I carefully pry it back and once it gets past a certain point the BCG will begin to move freely again and the round gets ejected.  This is my first ever AR15 pistol build in this caliber so need some advice to get this thing running flawlessly. I have not fired this yet. Your help will be greatly appreciated!

Specs
Generic PSA upper
10in Diamondback barrel
 Barrel Coating: Salt Bath Nitride
 Barrel Contour: Medium
 Barrel Length:10
 Barrel Material:4150 Chrome Moly Steel
 Caliber Gauge:7.62X39mm
 FeedRamps: M4
 Gas Seat Diameter: .750
 Gas System Length: Carbine
 Twist Rate: 1:9.5

Colt 7.62x39 BCG
Generic CH
Aero precision blem lower.
 KAK AR-15 H2 Heavy Buffer
 NBS Mil-Spec AR-15 Carbine Buffer [/li]

Roger

Don't worry about ejecting live rounds until you've fired the thing a few hundred times? It's not a "malfunction" unless it affects things during actual function, which dry-cycling is not.

You might check the line up of the Gas Tube to the Gas Key.   Could be slightly misaligned and "dragging".

As first post stated, take it out and try a few rounds.  Sometimes new guns aren't 'broken', they just need to 'break in'.

Define "Stuck BCG".  Stuck shut?  Stuck midway? ? ? ?

How are you "Prying it back"?  

Will it not release & open by pulling on the Charging Handle?

I am not able to clear it by pulling back. Using a screwdriver, i can push it back via the ejection port.

I'll be heading to the range to break it in.

Any possibility that the headspace is off? I do not have Go/No go gauges.

If you can't pull it back using the charging handle with a STRONG Grip & STRONG Pull then DO NOT SHOOT the RIFLE.

I'd suggest you pull the BCG & Disassemble it to check it out.  

It could be issues with the Cam Pin perhaps binding.  LUBE the BCG VERY WELL.   Check the orientation of the Cam Pin.  Also check where you have the side pin (little cotter pin) to see that you have it in the correct location relative to the firing pin.

Also - what ammo are you using in your "test fits"?   Any opportunity to try a few different brands / types to see if maybe your ammo is oversized?

Hope this helps, but if you are using tools at the ejection port to pry back the bolt carrier, something is definitely NOT kosher.


Edited - put some ammo in it, but do NOT use the Bolt Release to let the bolt fly shut.  

Just Gently Ride the charging handle forward so see if the shell will fully seat & seal.  If so, that is a good sign.  

If it doesn't, how much pressure do you need to apply to the Forward assist?  A light touch (normal) or a VERY HEAVY Push?

On a new rifle (parts not broken in yet) it wouldn't be abnormal for the bolt to hang just bit short of locking and the forward assist to lightly bump it with a brief easy touch.

But if you are having to Gorilla it shut, then I would guess your headspace is too tight or another issue is at play.

Hope this helps!

The most problematic thing in an AR Russian .308 build is the magazine

I have an old barrel that the bolt will not lock closed on some brands of steel case. Have to pry it open also to get the round out when it does it. Never had a problem with any brand brass case. I never checked but guess that the headspace is tight to slightly short on my barrel. My barrel is not worth the cost of a reamer or sending it off. At least it is a stainless barrel that I could have opened up a little if it needed it.

Okay, fellas. I appreciate the responses.  After changing ammo from monarch o tula, it started getting easier to eject the live round.  Here are some pictures, maybe it can help further break down the problem but I think the culprit is the Duramag as it got hung up when I slowly rode the BCG into the battery. If I rack and let it go, no issues though.

Bolt Carrier Group
BCG-1
BCG-2
BCG-3

Comparing BCG Colt vs DSA(nitrite)
Comparing BCG

Riding the BCG slowly into battery causes this
BCG (slow)
BCG (slow2)

This is what it looks like by racking and letting it go
Fast into battery

Monarch bullet
https://www.dropbox.com/s/j9n3qbwt8pre5h9/monarch%20bullet.jpg?dl=0

Tula bullet
https://www.dropbox.com/s/vyjxlv9mv54752k/tula%20bullet.jpg?dl=0

Upper
Upper -1
Upper-2
Upper Feed ramp

Did you clean your chamber and bore?

With bolt out, drop one of each round into the chamber.
Do they fall all the way in ?

Commie chambers are most likely loose as a goose,
(meant for the weapon to be thrown in the mud, run over by a tank, and made to be maintained by a 12 year old african),
so their ammo is probably not held to precise spec.s.
A barrel made here in the states probably tighter than some of the commie ammo.

All new firearms need to be cleaned and lubed prior to shooting them.

Never ride a bolt slowly on an AR-15 style rifle. They are designed to feed by completely releasing the charging handle after pulling it all the way to the rear, or tripping the bolt release. Don't baby it.

You may have insufficient headspace. I don't shoot steel cased ammo as a rule. I am sure if you are borderline with your headspace dimensions that steel case would be less forgiving than brass cased ammo.

I try to buy bolts from the same source I get my barrels. Manufacturing tolerances do exists, we are only talking about a thousandths of an inch, maybe two thousandths, if it will fit some ammo and not the other.

You might want to buy a 7.62x39mm go-gage. That represents the minimum allowable headspace dimension. Remove the extractor and the ejector before using it.

If you shoot the brand of ammo that currently does fit, eventually all of the ammo should fit because the bolt lugs and the barrel extension will wear a little bit giving you a little more room for clearance.

I did cleaned it and lubed prior to cycling but will put some more elbow grease. Got better after running a couple of cleaning pads through it.

I'll be ordering a headspace go gauge to to make sure I do my due diligence.

Took it out to the range two weeks ago and had light primer strikes so after order an enhanced fire pin and taking it out today, happy to report that all is well with it.  No malfunctions at all. Thanks for everyone's input. Happy shooting!