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FIRST thing OP needs to do is find out how this barrel is chambered. 5.56 and .223 are not the same thing. Without writing a page on info you can get from Google, the 5.56 chamber leade is "longer" which means you can safely shoot .223 in it but not vice versa. Meaning if he has a .223 chambered barrel he can be subject to unsafe pressures when firing 5.56. Someone should have discussed this as soon as he mentioned that he is interchanging rounds.

I noted the exact parts that I ordered in the OP along with the exact ammo I was shooting. It is a 5.56 barrel. I know this is about crossing t's and dotting i's, but I would not have put a 5.56 round through a barrel that wasnt stamped "5.56".

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That being said, if this is a headspace issue then you have a potentially dangerous situation. Remember that you are holding a metal tube up to your face and initiating explosions at thousands of pounds of pressure. Not something to be treated lightly.

Oh yea, definitely. That's why I came here for help and will not fire another round until I can get this problem figured out. I certainly want to be cautious.

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I would check assembly of the hammer spring to see if it is oriented correctly first. Incorrect placement of the spring legs will result in half power hammer fall and failure to ignite mil primers. Common mistake by home assemblers.

I bought the lower completely assembled from PSA so I would hope that they would have the competence to not have this wrong prior to shipping it to a customer.

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Check the chambering, verify correct assembly of your fire control components and then send the rifle to PSA or a gunsmith if headspace is suspected. Not to be insulting but this isn't something a first timer should be fooling with.

No offense taken. I am a nube when it comes to AR's, but Im trying to learn. I called PSA yesterday but it was after hours for their Compliance Dept.

According to many of the responses it seems my problem could be one of these...
-headspace issue which is potentially dangerous and should be taken care of by PSA and/or a gunsmith because of my incompetence (seems like this potential problem should be taken care of/figured out before moving on to anything else. I will call PSA today to discuss)
-misorientated hammer spring
-possibly a new H2 buffer swap (based off of what Clames said)

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Before you chasing your tail with a headspace gauge that will tell you little to nothing, go find another action spring (the misnamed buffer spring) and a H2 buffer to swap in and try 5.56 again. According to PSA you have a standard weight buffer which isn't exactly the best choice for a carbine

Spikes ST-T2 Heavy Buffer If determined to be the problem, I assume this would be the part to upgrade?

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Posted by Clames

Member since Oct 2010

16728 posts

Posted on 1/13/15 at 10:02 am to dnm3305

I usually suggest a H2 buffer in carbines and I run that exact one from Spikes in mine. If you have access to a digital scale (kitchen one is fine) I would weigh your buffer. Then check the action spring for proper OAL, should be 10-1/16" to 11-1/4". Springs are one of the parts in AR's that have the most variability in terms of dimension and material. Any change can impact the K-value and cause problems with a given rifle. Stainless and chrome-silicon action springs are preferred but some companies use plain high-carbon steel springs which are cheaper but have more variation. Could be a pinched or misaligned gas tube/gas block but that is not a common issue with factory rifles built with jigs and especially those with standard front sight bases. I would find a friend with a similar rifle with a H1 or H2 buffer and ask to borrow his parts to test. You are going to have to post a lot of pictures of the rifle's parts, the ammo, and spent cases (sides and base).

This post was edited on 1/13/15 at 10:06 am

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