AR help / suggestions

[mountainman]

What he said!

[Fl0und3rz]

I'd suspect a sticky or obstructed extractor causing the round to start to chamber at too high an angle to the chamber. As the round is coming off the magazine something appears to be preventing the back end of the case from coming up to the centerline of the bolt as it chambers. I had a similar issue with a marlin 1895, and the rounds had similar scratching.  A sticky extractor would explain the marks on case rim as the extractor is being forced over the rim. 

[mrolen]

I would start by full strip and clean of the bolt. some lube is to heavy in cold weather I have experienced this with frog lube. Try a different mag and possibly a new BCG, that is where i start with an ar with problems.

[Heredoggydoggy]

I would start by full strip and clean of the bolt. some lube is to heavy in cold weather I have experienced this with frog lube. Try a different mag and possibly a new BCG, that is where i start with an ar with problems.

   I'd suspect a lube problem.  We've had some very cold temperatures lately, and some lubes don't handle cold very well! 

[snowpack]

The difficulty for closing the bolt all the way, even using assist does sound like lube issues.  It makes it difficult to rotate and lock the bolt (and unlock it too).  That last 1/4 inch on closing is horrible if sticky.  The scratches on the ammo, factory ammo, looked like a bad feed angle, so I was thinking magazine alignment.

[jrebel]

Thanks for all the information.  I have a few upgrades on order now and I will be doing another thorough cleaning and better lubing with a new lube.  I can't imagine it has anything to do with the magazines as the mags have worked flawlessly prior to these episodes.  If the upgrades / cleaning / lube does not work I will try a different bolt / bolt carrier. 

For the diagnostic purposes I will try one thing and shoot, then try another and so on....I will update with the progress.  I hope I can figure this out.  I will say this...as much as I have enjoyed building and shooting my AR, I have never has a problem with my AK.  This AR thing can be frustrating.   

[6.8mmARHunter]

I know precisely what your problem is...

You have to swear off the 49ers. Everything will be good after that.

Totally kidding...

I've got nothing else.

[jrebel]

When a bullet looked like that. It's either the mag isn't seating correctly or for some reason the bullet is riding the front of a metal mag when it's feeding either that or it's a feed ramp issue as in m4 cuts on the receiver but not on the barrel?? Hmmmmmmmm. Look into the feed ramp area and see if it is a smooth transition from the M4 cuts in the receiver to the cuts in the barrel.

OK...Well after a lot of tinkering and a few upgrades, I think I know what the problem is.  My bullets and cases are being scared by the lugs on my m4 feed ramps.  Next step will be to polish (find someone that knows how to polish) feed ramps and clean up the ramps where they meet the lugs.  My set up is a rifle upper with m4 ramp barrel extension.  My magpul magazines seat the bullets high enough that the bullet is not coming into contact with the receiver at all.  The copper and brass scaring is coming from the harsh angles at the ramp / lug area of the barrel extension. 

If I am right....this should fix all my problems.  I will post after I have had the ramps polished.

jrebel

[Biggerhammer]

When you posted the gouged up cartridge pics, I knew it has to be a feeding issue with the receiver cuts or the barrel extension cuts.

[jrebel]

Update....Problem solved!!!! 

Last week I spent a couple hours watching youtube videos and learning how to polish ramps and work on AR's.  Today I took the dremel and got to work (figured the worst I was going to do is mess up a barrel extension and maybe an upper) .  Spent a couple hours polishing the feed ramps.  Now they look really shine and are awfully pretty.  I readdressed the bolt and bolt carrier; recleaning and oiling the living piss out of it.  Everything was smooth as butter.  Next step was to feed ammo and see what happens.  I place a loaded mag in the well (pointing my muzzle toward the floor) and feed a round................JAM  !!  Try again.........JAM !!  Now I am pissed.  Inspect the brass and notice the makings on the bullet and brass are significantly better / lighter.  The brass on the head stamp is still marked up pretty well.  So needless to say I am now really pissed off. 

I decide to just buy a new bolt carrier group.  Drive to one of my new favorite stores (Stans Merry Mart) and purchase a nickle boron bolt carrier group.  Come home and replace the original bolt carier group.  Guess what......Cycled a complete mag with no issues.  Bullets still have very minor markings but all in all everything looks good.  Head stamp has no marks.  Problem solved....for some reason my bolt / extractor has gone bad.  Now to replace the extractor on the old bolt and see what happens.  If that does not solve the problem I will buy a new bolt.   If that does not fix the problem I will sell the complete pile of mess to the highest bidder!!  

jrebel

[Fl0und3rz]

Good to hear.  Please update with the extractor/bolt troubleshooting results, too.

[jay.sharkbait]

Update....Problem solved!!!! 

Last week I spent a couple hours watching youtube videos and learning how to polish ramps and work on AR's.  Today I took the dremel and got to work (figured the worst I was going to do is mess up a barrel extension and maybe an upper) .  Spent a couple hours polishing the feed ramps.  Now they look really shine and are awfully pretty.  I readdressed the bolt and bolt carrier; recleaning and oiling the living piss out of it.  Everything was smooth as butter.  Next step was to feed ammo and see what happens.  I place a loaded mag in the well (pointing my muzzle toward the floor) and feed a round................JAM  !!  Try again.........JAM !!  Now I am pissed.  Inspect the brass and notice the makings on the bullet and brass are significantly better / lighter.  The brass on the head stamp is still marked up pretty well.  So needless to say I am now really pissed off. 

I decide to just buy a new bolt carrier group.  Drive to one of my new favorite stores (Stans Merry Mart) and purchase a nickle boron bolt carrier group.  Come home and replace the original bolt carier group.  Guess what......Cycled a complete mag with no issues.  Bullets still have very minor markings but all in all everything looks good.  Head stamp has no marks.  Problem solved....for some reason my bolt / extractor has gone bad.  Now to replace the extractor on the old bolt and see what happens.  If that does not solve the problem I will buy a new bolt.   If that does not fix the problem I will sell the complete pile of mess to the highest bidder!!  

jrebel

When you cycled the rounds this last time were they rounds that had been previously "tested" in the rifle?

[jrebel]

Update....Problem solved!!!! 

Last week I spent a couple hours watching youtube videos and learning how to polish ramps and work on AR's.  Today I took the dremel and got to work (figured the worst I was going to do is mess up a barrel extension and maybe an upper) .  Spent a couple hours polishing the feed ramps.  Now they look really shine and are awfully pretty.  I readdressed the bolt and bolt carrier; recleaning and oiling the living piss out of it.  Everything was smooth as butter.  Next step was to feed ammo and see what happens.  I place a loaded mag in the well (pointing my muzzle toward the floor) and feed a round................JAM  !!  Try again.........JAM !!  Now I am pissed.  Inspect the brass and notice the makings on the bullet and brass are significantly better / lighter.  The brass on the head stamp is still marked up pretty well.  So needless to say I am now really pissed off. 

I decide to just buy a new bolt carrier group.  Drive to one of my new favorite stores (Stans Merry Mart) and purchase a nickle boron bolt carrier group.  Come home and replace the original bolt carier group.  Guess what......Cycled a complete mag with no issues.  Bullets still have very minor markings but all in all everything looks good.  Head stamp has no marks.  Problem solved....for some reason my bolt / extractor has gone bad.  Now to replace the extractor on the old bolt and see what happens.  If that does not solve the problem I will buy a new bolt.   If that does not fix the problem I will sell the complete pile of mess to the highest bidder!!  

jrebel

When you cycled the rounds this last time were they rounds that had been previously "tested" in the rifle?

Same manufacturer and same ammo, but batch..... (if that makes sense).   The other stuff that was jamming up has some horrible damage to the brass on the head stamp.  I am not to sure it will feed in anything at this point...it may need to be trashed. 

Anyone else ever have a bolt / extractor just go bad???  Worked great for the first 3-400 rounds.