Took my "new" pre-ban Oly out to play yesterday.  I had 7 mags, (6 milsurp and 1 orlite) fully loaded with 30 rounds.  I had two different FTF's.

a) This one was, I think, mag-related.  The first round would feed.  The next (on the left side of the mag) would run straight forward and the nose of the bullet would smash into the front of the mag.  It wouldn't rise up into the chamber at all.  Black follower in the mag (all mine have black followers except one).  Does this sound like a weak spring or a problem with the feed lips?  Only the first couple rounds on the left side of the mag would do this - and when I only loaded 10 rounds, the mag worked fine.

b)  This one I'm not sure about.  The rounds, from the right  side of the mag, would get picked up by the bolt, but only move forward about 1/2 inch before stopping.  However, the forward assist would move the round into the chamber.  This ould only happen on a full mag.  So I'm thinking the recoil spring is weak - not enough oomph to strip the first round out of a full mag.  Again, when I loaded the mags with 10 rounds, I ran 7 mags through without a problem.  

Any thoughts?  I'm kinda bummed out, because I was totally psyched about getting the pre-ban and I couldn't seem to get it humming.  

Thanks,

Eric

The down and dirty(pun intended) solution, clean the rifle.  It has been sitting and the assembly grease has hardened.  Use CLP to clean the grease out of the rifle, including the gas tube, buffer, and receiver extension.

The mags could be dirty too. If they were cleaned in a solvent tank, the grease/solvent has turned into a film that will need to be wiped out of the mag.

You state that the mags have black followers. The green type are a little better regarding feeding, but the mag needs to be cleaned and the spring check before you start thinking about changing the followers. If the mags are still a problem after cleaning, and the springs are still good, I can post a tweak that will solve the top round binding without having to install the green followers.

With the rifle/mags fleshly cleaned, and lubed with a fresh coat of CLP, it should be a happy/humming rifle.

Note: If the rifle was virgin when you got it, then the upper parts are new and rough.  The use of a little extra CLP on the bearing surfaces will keep the degreased parts from binding and allow the parts to polish themselves without jamming during break in.

Hope this helps.

Thanks, Dano.  The mags are clean, they've functioned fine in my other AR.  I did clean and lube the rifle before firing, but didn't get into the buffer tube area.  I'll clean that out.

I did notice that, although the lower is about 11 years old, the upper was much newer and the bolt carrier didn't seem to have much wear.  It might need some breaking in to get it running smooth.  

What's a good way to check to see if the mag springs are good?

eswanson, I could use some further info on the FTF in part B of your post, where the right side first round fails but the FA chambers it.
Does this happen with:
Bolt/Carrier locked back,
Mag inserted,
Bolt release actuated,
Bolt/carrier freely goes forward and round jams.

And does it happen on subsequnt rounds during fire?

And are fired rounds ejecting from the gun?

Royce, I had no failures to eject.  The "b" FTF occurred with a full mag only.  And the sequence was as you laid out - mag inserted with bolt carrier back, bolt release pushed, bolt rides forward.

I was playing with the rifle this evening in the basement, and I think the problem was a combination of underlubrication on the bolt carrier and the fact that the BC has kind of a rough finish.  Seems like the parkerizing is rough.  I think if I had it better lubed it might have worked better.  Like I said, it didn't seem as thought the upper had too many rounds through it (before I put 600 through on Sunday), so maybe it just needs to break in a little.

Tonight, when I would retract the charging handle and ride it forward without a mag inserted, the bolt carrier would hang up about halfway home.  If I let the charging handle go, instead of riding it forward, the bolt would go fully into battery.    

Eswanson,
Your newfound problem is that the hammer is catching the firing pin on the return stroke, or the hammer is binding up on the disconnector.

Check the disconnector just behind the hook. See if there is a bright line where the hammer hook has been tagging the disconnector.  If there is a line, use a file and remove some metal from the tail of the hammer to prevent binding/contact.

As for the hammer catching the firing pin on the return stroke. Check the top, back of the hammer for signs of wear. The hammer may be riding a little higher than normal. If this is the problem, again use a file and remove a little metal from the top/back of the hammer where it is catching the firing pin. You don't need to go buck wild, just roll file to remove a little height of the cocked hammer.

Now for the rough surfaces, we have taken a vote and decided that you must break the rifle in the military way.  
This means that you have to carry the rifle around with you, like a third testicle, never firing the rifle, and having to clean the rifle at least three times a day.  It helps if you hand the rifle to you're wife and have her throw it back to you, telling you that it is still filthy, even after you have slaved cleaning the thing for a hour.
In a few weeks, the rifle will nicely polished (all the cleaning) and be ready to fire.

eswanson, would you take a look and see if the disconnector has a 'wear' spot where the hammer tail might be hitting it?  Before you take a little of the top [of the hammer]make sure you don't have a long hammer tail which is hittingthe base of the diconnector.When that happens, the hammer does not go down low enough to clear teh carrier and so rubs on the carrier, slowing [or even stopping] it.  Your symptons are not quite right for this problem, but check it anyway.
Also, it is common for a carrier to hang up when you guide it forward by hand.  That is not the way the gun was meant to function so the test is not valid.  
It is very rare for a buffer spring to go bad, but you could have one that has been clipped short by some good-intentioned sole who thought he knew something about AR's and attempted to fix another problem with that 'band-aid'.
You could also have the wrong buffer.
When you say your 'new' pre-ban, can you be more specific.  Did it come in its original box with all original paperwork?  Was it from a dealer or private?  Just curious.

Dano and Royce, thanks for your responses.  I've been off the board for a few days.

Dano, you win the prize for describing my hammer and disconnector.  The disconnector showed the bright lines, and the top of the hammer showed wear.  I relieved a little from the hammer "hook" so it wouldn't hit the disconnector, but the top of the hammer was still binding on the firing pin, so I relieved a little off there too.  So I guess the hammer was just riding a little high.

After putting it all back together, I can cycle the bolt without getting any resistance, so it looks good.  

Thanks again for the assistance!

Edited to add - Royce, it's a new pre-ban to me.  The lower shows signs of wear, but the upper is not original to the lower (different finishes) and looks to be considerably newer.  No original box or paperwork.  Bought it off the equipment exchange.

This is one of the reasons that I love this board.  Learn something new every day -- and it isn't always about AR15's (also advice on investing, plumbing, lawn care, cars, dinner guns , etc.).

EDITED for typo.

Any sign of contact with the "collar" of the firing pin? The M-16 firing pin has a bigger "collar" than the AR-15 pin and sometimes drags on the hammer.

Quoted: Any sign of contact with the "collar" of the firing pin? The M-16 firing pin has a bigger "collar" than the AR-15 pin and sometimes drags on the hammer.

Nope.  Strangely enough, the firing pin didn't show any odd signs of wear, just the hammer.