OK fellow AR15'ers, I'm in some trouble.
Here's my issue. It's sotra long, but a mind twister nonoftheless.

I own a 20" HBAR Bushy.

Owned the weapon for over 5 months now.
Not had any issue's, until I sent it back to bushy to get the barrel re-indexed.

I've received it back about 3 weeks ago back from bushy, took it apart cleaned it. Took it shooting last week for first time since its return from bushy. Went through one 30 round clip without a hiccup.
After that first clip, problems!
It would either not chamber a round (bolt going right over top of round while in clip), or the bolt slam into a round that was half-way into the chamber.
I also noticed that the bolt catch wasn't catching on the last round.

So I took it home and cleaned it again and shot it today for the first time since last week.
Same thing!!
First clip worked perfectly fine, bolt still didn't catch. Bolt would either pass right over round or bolt would slam into a half chambered round.
I've used 3 mags since I've owned it, 2 USGI's and 1 Thermold. I've used nothing but SA M193 since I've owned it as well. So as far as it seem's the mags and clips are covered, they both didn't have any issue's for 5 months.

I will say that I installed a bushmaster spring kit, but I only installed the 2 trigger springs. I don't see how trigger springs could cause this. I also installed a accu-wedge after I got it back from bushy, but that was the first thing I took out after it started having these issue's, so that can't be it.

What do you guys think? I have no idea's, other then bushy did something to cause this.

your problem is your using clips. try some mags

I did, then I tried some clips and it didn't work either.

When I look into the chamber, the bolt is slammed into the side of the round. It looks like the angle is all wrong, the actual bullet is caught up in the chamber, near the top lugs.

WoW...!!

absolutely no mention of ammo being used, how many different brands types ammo were you using, mixed batch ? all one brand ? most feeding problems come from ammo that just will NOT function in some rifles, even after a few mags of the stuff.....

I know you say that you ruled out your mags, but this SERIOUSLY sounds like a mag problem.

Best guess-  Weak springs causing round to not rise fast enough.
Second guess- Bad followers causing hangups and "tipping" within the mag.

...But it REALLY sounds like weak springs.

 Check out some other mags.

Short stroking possible, but sounds unlikely if the bolt was overriding the case halfway chambered.

Goodwill,
         -Dirtfarmer

Two possible simple fixes:

Might be a weak mag spring.  I have an old 20-rd. Adventure Line that always misfeeds the last round.

Might be a loose gas key.  When I was new to ARs, I would remove the gas key when cleaning.  It got too oiled up and would become loose when firing, so that by the 40th round or so, I'd have bolt-overs and misfeeds.

Quoted: WoW...!! absolutely no mention of ammo being used, how many different brands types ammo were you using, mixed batch ? all one brand ? most feeding problems come from ammo that just will NOT function in some rifles, even after a few mags of the stuff.....

I could've sworn I said I've used nothing but SA M193, since day one in my post. Thanks for your response nonoftheless.

Quoted: I know you say that you ruled out your mags, but this SERIOUSLY sounds like a mag problem. Best guess-  Weak springs causing round to not rise fast enough. Second guess- Bad followers causing hangups and "tipping" within the mag. ...But it REALLY sounds like weak springs.  Check out some other mags. Short stroking possible, but sounds unlikely if the bolt was overriding the case halfway chambered. Goodwill,          -Dirtfarmer

Yea, my thoughts as well.
It seems to short stroke half the time (bolt goes right over rounds without enter a round into chamber), then next cycle will be a jammed round (bolt hitting the side of a over-angled round jamming into top of chamber)

Weird stuff I tell you.
I have 5 used USGI mags that I haven't broken in yet, I'll try those, but I seriously don't see how my 3 mags that function flawlessly for 3000 rounds of SA M193 before it went to bushy, could've went "BAD" while the upper was gone for 2 weeks at bushy to get barrel re-indexed.

Next week I'll try some USGI's that I have.
Without being an armourer, to me it seems to be a gas leak somewhere by the way its acting.
I made sure the gas rings were staggered 120 degrees.
How does one rule out a gas issue?

I know the 2 main components are the gas tube and the carrier key.

While I'm on this topic could someone clear something up for me please.

How does the gas enter the gas tube?
It runs across the top of barrel, the only thing I can think of is that there's a small hole somewhere in the middle of the barrel on the top, but when I look down the barrel (breech end of course) I don't see a hole anywhere.

The hole is very small and hard to see, but it is there.

I have to get my Bushmaster re-indexed (way over to the right) but have been reluctant to send it back to Bushmaster.  All these Bushmaster problems, combined with a barrel and indexing problem I have with my new Bushmaster, is really disappointing me, considering the rifle cost me over $800.00

I think it's an intelligent deduction that when they re-indexed your barrel, they messed up the gas tube connection to the barrel and as you suspect you're not getting the full gas blast for the rifle to function.  Makes sense as this is the front sight and what they muck with when correcting the index problem.

I called bushmaster and talked to a fellow named Jim. Cool guy and answered all of my question and even explained to me from beginning to end the entire cycle of the AR.

After telling him my issue, he agree'd 100% there is a gas leak somewhere.

I asked him, "what about the first 30 rounds working great".
He thinks when I clean it , the oil finds its way into the carrier key bolts, it is enough to
keep a "seal", until I shoot it couple times and the oil is all dried up by then, and at that point, there's no longer a seal.

So I say, "so you think this issue happening right after I get it back from you guys (bushmaster) and this issue is a coincident?"

He says, "yes".

He says to look at the screws that hold the carrier key to the bolt carrier. He thinks one of them is either cracked or needs to be tighten.

I have a hard time believing that the two are not connected, but nonetheless, he was nothing but nice, offered nothing but help, so I'll try what he thinks it is and I'll go from there.
I'll update this post tonight to tell you if Jim was right or not, for those that actually care about my issue.

I never thought about looking for the gas tube before.  I just did after reading murderSHO45's post, and I can't see it.  I looked down the barrel both ways.  That thing must be the size of a pinprick.  Does anyone know how big it is?