7.62x39 Bushmaster upper not consistently firing

[Remadl700]

My bad on the upper make!!! I was told it was an Oly.

We put this brand new upper on my BM lower and it won't consistently fire the rounds. We used two types of ammo and changed the firing pins out. Also placed the 223 upper back on and had no problems with 223 ammo or firing pin. The pins look to be cratering the primer fairly well.

.??????? :huh:

Update:
12-27 : went to Hornady ammo and a JP enterprises spring kit.
Result : same issue FTF on 4 different types of ammo

The purpose to buying this is to have platform that can reliably fire 7.62x39 ammo without having a different weapon......

Update 2: put in the Heavy Hammer spring and milled a couple thousands from the shoulder of the firing pin. Not one FTF! In 60 rounds plus 2 more mags on the Slide Fire stock .......in the Rock And Roll setting

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[nubus]

Are you using the heavier hammer spring and the 7.62x39 firing pin? If you are using steel cased ammo (wolf, etc.) good luck.
I have had poor luck with steel ammo in AR-15s regardless of manufacture, hard primers and stuck cases repeatedly.
Just my personal experience, but the hammer spring can make all the difference.

 

[eldbillbo]

its feeding right? just light primer strikes? or?

 

[Eric911]

Contact Oly Arms and give them the details.
Andy - [email protected]
Warranty/Repair
(800) 228-3471

Often an extra-power hammer spring is required, like the ones from Wolff (<broken link removed>). Also, double check the installation of the existing hammer spring and ensure it is configured like the one depicted below. Note the long legs of the hammer spring wind from underneath and rest on the top of the trigger pin.

 

[Remadl700]

Thank you!

My bad it is a Bushmaster. I was told it was an Oly and did pay it any more attention.....Piss poor excuse but it's all I have got right now.