AR15 won't fire (no, it's not the springs)

[Zoolander]

Used different ammo, swapped lowers for one I know works and had no luck so I also swapped BCGs for one I know works and still nothing. Hoping for input as to what I may have missed, this is past my troubleshooting knowledge at this point.

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[Colefoz]

Is your firing pin and cotter pin in the correct position? If you have the flat surface of the firing pin behind the cotter pin, it will not travel forward when struck. May seem dumb but I saw a buddy do that.

 

[nwcollectors]

Wont fire, as in, wont strike?

 

[v0lcom13sn0w]

what do you mean? the hammer doesnt fall?


sounds like the BCG isnt going into battery. ive had a too long gas tube before. also had a burr on the barrel extension not allowing the bolt to engage the barrel extensions correctly.

 

[Ops]

how about some detail

 

[nwcollectors]

Gas tube is what i was thinking

 

[308]

Gas tube bent up or slightly off to one side and wont mate with the gas key?

 

[Unicykle]

you used 2 differnt lowers and 2 differnt bolt carrier groups? He should be able to tell if its going into battery buy looking but Did you try using the forward assist? Is this a new gun or a used one?

 

[v0lcom13sn0w]

lets think about this...swapped lowers. ruled out everything it could be on a lower, swapped BCG...so its not the firing pin. that leaves only the gas tube or barrel extension.

 

[v0lcom13sn0w]

or ridiculously bad headspacing or wrong caliber ammo but that's pretty unlikely.

 

[Zoolander]

My thought was something with the barrel. Upper was purchased as a complete 20" upper from PSA.

As for what it does, you pull the trigger and the only noise is "click".

 

[eldbillbo]

What about the ammo? look at the primers are they flush set deep? Correct barrel? they didn't accidentally send you something other than a 5.56 did they? Don't just trust their markings.

 

[eldbillbo]

What happens when you pull the charging handle back does it extract and eject the shell? Is there any unusual resistance where the key is scraping the gas tube?

 

[Zoolander]

Tried different brass ammo, even tried Tula for the hell of it. When you pull the charging handle back it will either eject the shell or jam, both have happened. Yanking on the charging handle a few times will eventually clear the round.

 

[Unicykle]

As stated i think the previous posters were correct in stating the gas
Tube in the upper and the bolt carrier key are conflicting in some way keeping it out of battery. Check the gas tube in the upper to make sure its centered and round with nothing funky happening if it looks good with your upper and lower appart, inserting the bolt carrier into the upper and tilt the barrel down slightly the bolt carrier should slide till the lugs touch and just slight pressure should fully seat the bolt carrier moving the bolt carrier about 3/8 of an inch locking the lugs into full battery. Im betting it wont pass one of these tests.

 

[Capn Jack]

"Yanking on the charging handle a few times will eventually clear the round."

Unless I've missed it, you haven't checked for proper head spacing.

 

[CLee0507]

Pics of the inside would help. Chamber area and gas tube/bolt

 

[eldbillbo]

Try this with it unloaded point the barrel to the floor drop the bolt carrier group into the receiver see what it does the bolt should partially close then press it to lock the lugs you should be able to feel the lugs lock and it should take very little effort to do it. In fact, in some cases, a bolt will lock up just by dropping it in. If its hanging up its probably a misaligned gas tube which is very common. But you should feel it lock.

this and visual inspection should be able to determine if its a misaligned gas tube and I have even seen an out of spec gas key once that caused this problem as well.

 

[MrMillspecer]

Does a cartridge drop into the chamber ? Could be out of spec.

 

[P7M13]

Um, pre-assembled from PSA? Sounds like it was "built on a Friday" and completely bypassed operational check.