Feeding issues

[Burks194]

Hello all new to this forum.

My problem is this.  I milled an 80% lower and it works as so, but when married to a raw/blonde upper receiver with an A2 buffer tube/spring kit using a nickel boron BCG on a 18" barrel with non-adjustable gas block.....it fires 2 rounds flawless but the third fails to fully chamber, every time with a plethora of rounds.  Everything is properly lubed.  I have built several rifles in the 5.56 and 204 variety but this is my first 80% lower build in the 308 variety.  I thought it was the lower but everything was milled to mil-spec and checked twice.  I'm at a loss and refuse to proceed any further till this issue is resolved.  Please help.  I am very inclinded with my hand and tools.  Just need a good starting point.  Thanks

[jtallen83]

5 minutes ago, Burks194 said:

I thought it was the lower but everything was milled to mil-spec and checked twice.

308 AR milled to mil-spec? No such standard for the big fram AR's. The Guru's here will need more info and pictures. Brand of parts, gas system, does it lock back after firing a single round, what does the jam look like, lots of questions to clarify here. 

[Burks194]

 By mil spec I mean the parmeters of a factory lower per various searches.  With one round it will lock back and two it will lock back but the third hangs up.  The jam/hang up is what I would call a half chamber.  Gas system is rifle length.   Parts are midway cheapies.  Barrel and extention are Anderson.  BCG was from Primary Arms and dont remember the brand.  To late to fire the weapn to get a picture.  I'm just baffled why two rounds fire flawless and eject but the third fails to chamber/half chamber.  Tried various brands of rounds with the same results so thats why I'm  perplexed. 

[Armed Eye Doc]

Have you used different magazines and different brands of mags?  Will it hand cycle through three rounds? 

The gurus will want measurements of the buffer system... internal depth of tube, weight and length of buffer, relaxed length and number of coils of the spring.

[98Z5V]

2 hours ago, Armed Eye Doc said:

Have you used different magazines and different brands of mags?

This.

Measure the buffer - it's a rifle buffer, so it needs to be 5.200" long for a .308AR (not RRA).  I don't think it's buffer, though.  I'm leaning towards a mag-related issue here. It's the mag spring, or the feedlip angle, or the rounds are too long for the mag and jamming up at the front of it.  Something like this.

[survivalshop]

   What ammo are you using ?

   What is a Raw/Blonde Upper Receiver ?

   Has the Rifle had the Head Space checked ?

  Some NIB Bolts are coated incorrectly & may cause issues when the rifle heats up & also I have seen them cause tight Head Space issues .

  Most feeding issues are Magazine related , but you say the Cartridge is not feeding all the way , what do you mean by that ? Is it in the Chamber , half way in , not fed into the Chamber ? A Photo of the FTF  would help a lot .