The weapon:
Palmetto Armory (Oly c.1980) CAR-15 w/ 11.5" barrel

The symptoms:
1) Bolt fails to advance round randomly every 10 rounds or so and bullet tip or case edge gets stuck below the lip of the ramp (forward assist has no effect).
2) Plenty of blow-by carbon at the front of the gas tube.
3) Magazine is "tight" (won't click in without hard push).

Any suggestions as to which of these symptoms are related to each other?

My 1974 Colt A2 is so smooth and consistent it makes me giddy.  But this newly acquired Palmetto might need to go away.

Got a pic???  Would like to see the gas tube at the FSP beneath the handguards.

Tried other magazines?  Other bolt/carrier assemblies?

Send the lower to Oly had have them remanufacture it with one of their forged lowers.
It will still have your serial number.

The Palmetto lowers look cool, but they are worn out.

I have not been out to the range yet, but I did the following:

1) Polished the ramps.
2) Put a drop or 2 of Loctite 690 around gas tube where it enters sight post.
3) Noticed the "tight magazine" was only when bolt was forward.
4) Noticed the buffer face was all dinged up around the edges (enough to have it fall out without depressing the retaining pin).  The spring is probably kaput also.

I ordered a new buffer & spring.  

I advanced and ejected a couple full magazines and it seems smoother now, especially when I put the magazine in with bolt back, but who knows until I get to the range next week.

The carbon from firing should seal in the gas tube.I wouldnt use lock tite there.Use a brand new mag.And when you say mag is tight is it just during insertion into the well or loaded to capacity or empty?

Quoted: The carbon from firing should seal in the gas tube.I wouldnt use lock tite there.Use a brand new mag.And when you say mag is tight is it just during insertion into the well or loaded to capacity or empty?

I figured carbon would build up, but wanted to give it something to build on. I used VERY little loctite and made sure none was in the barrel.

I tried several different mags new and used, loaded and not.  It's tight just during insertion and only when bolt is forward.  It's pressing against something that keeps the catch from clicking in.

I think my biggest issue is the buffer/spring.  I failed to mention in my first post that I had a 2 shot "burst" from a bolt bounce....?  ...no finger involved.

I identified the "tight magazine" issue...  A full magazine has about 1/8 inch of give to the bottom plate stop.  On this Palmetto, that aint enough.  The bolt carrier is just too low.  If I take 1 round out, it clicks in... if I take out 2 rounds it feels perfect.

Stupid Question:  Would it do any good to polish the bottom of the bolt carrier?

[sigh]

Send the lower to Oly had have them remanufacture it with one of their forged lowers.
It will still have your serial number.

The Palmetto lowers look cool, but they are worn out.

Been there, done that, you can keep fucking around with the Palmetto for as long as you want....

I spoke face-to-face with the Oly guys today at the gun show in Tacoma....

They no longer mess with old lowers and definately won't re-serialize one anymore.

The option... buy a new one.

Every AR-15\M-16 I've ever used has some trouble locking a full magazine in with a closed bolt.The rifle was designed to be loaded with the bolt open. The range command for loading an M-16 is "with the bolt remaining open, load".

The problem with the round striking too low is due to either the magazine pitching foward in the well, or the follower nose diving. What brand of magazine and what is the condition of the spring and the color of the follower? M-16's are known for this exact problem when used with blanks.

Quoted: I identified the "tight magazine" issue...  A full magazine has about 1/8 inch of give to the bottom plate stop.  On this Palmetto, that aint enough.  The bolt carrier is just too low.  If I take 1 round out, it clicks in... if I take out 2 rounds it feels perfect. Stupid Question:  Would it do any good to polish the bottom of the bolt carrier?

The problem with the round striking too low is due to either the magazine pitching foward in the well, or the follower nose diving. What brand of magazine and what is the condition of the spring and the color of the follower? M-16's are known for this exact problem when used with blanks.

Sgt_Gold,

I was using a Pearson but I tried my new Colts and they had a little more clearance, but eventually produced the same result.  I have all manner of Colt mags (Green, Black, Metal Followers), but have not tried all.   The upper/lower slop was pretty extreme, so I put an "accu wedge" in and that tightened things up (which also drives the mag angle up).  I will have a new buffer spring in 2 days and I'll hit the range to test all these tweeks.

THE REST OF THE STORY.....

I performed all these "fixes"... new spring, new buffer, polished ramps, wedges, new mags, inserting mags w/ bolt open, hoping, praying, meditating, etc.

Then yesterday, I went to the range and... the problem GOT WORSE!?

But, on one of the bolt cycles, the bolt catch stopped the bolt from advancing (with plenty of rounds in mag)...  That was the hint I needed.

I checked the bolt catch.  It was waivin' in the wind like there was no spring.  After taking it out, I could see that at some point, the bolt carrier had smacked the the bolt catch while traveling rearward on a live round and it jammed the detent pin in the hole and permanently crimped it in place (this probably happened more than once).

I reamed the hole out, put it back together (hey, the spring works now!) and everything feels MUCH better.

This noob learns fast, but sometimes to takes a few cycles.

I think I'm lucky I didn't really break something.

Lesson Learned: "The bolt has many obstacles... better make sure they are out of the way at the right times."

That is sooooooooo Feng Shui

Quoted: Lesson Learned: "The bolt has many obstacles... better make sure they are out of the way at the right times."

Thats just what I was about to tell you to check next.  Well, that and to buy a COLT.

Quoted: Thats just what I was about to tell you to check next.  Well, that and to buy a COLT. hr

Got one already. hatyou.

http://www.auctionadvisory.com/ar15/ar15colt2.jpg