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Posted: 4/6/2025 8:22:21 PM EDT
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Or is it base over bolt? I have a Palmetto A4 20” that I put together before Covid and it’s been laying around ever since. Decided to take it out today. Shot 90 rounds and had 3 bolt over base malfunctions. Brass shavings all over the mouth of the chamber:  I’m confident it’s not the magazines. Ammo was that Federal XM193 “American Eagle” that Wal-Mart use to sell before 2019. Just a plain unsupressed riflle. Nothing exciting. Any ideas? |
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Originally Posted By K5FAL: Or is it base over bolt? I have a Palmetto A4 20” that I put together before Covid and it’s been laying around ever since. Decided to take it out today. Shot 90 rounds and had 3 bolt over base malfunctions. Brass shavings all over the mouth of the chamber: https://imagizer.imageshack.com/img924/346/gHed1N.png I’m confident it’s not the magazines. Ammo was that Federal XM193 “American Eagle” that Wal-Mart use to sell before 2019. Just a plain unsupressed riflle. Nothing exciting. Any ideas? What magazines? |
I sell firearms produced by the finest child labor in the world, be it Filipino, Muslim, Mormon, Arizonan, or Texan.
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Start with good know usgi mags, and pull them down to give they a good CLP cleaning from the start. As for mag catch, remove it, shove just the body of the mag into the well until is bottoms out of the bottom of the carrier, then look into the non ejection side of the bolt catch slot, to see where the mag slot for the catch is against bottom of slot. Hence if way up, this means mag will be way down, and could be the reason that bolt is over shooting the rim of the case if mag is recovering correctly. If that looks fine, with the mag feed lips only 1/16" off the bottom of the carrier when locked into the well via the mag catch, then when you reinstall the mag catch, make sure that the threaded part of the catch end, if flush with the face of the release button. Now if all the above it good, and its a problem with the bolt not coming back far enough to get behind the rim of the case, then need to start looking for gas leaks, or even just the fouling so bad in the chamber, that it cause spent case clean ejections from the chamber in the end problems. Note gas leaks could be carrier key to top of carrier, gas block to barrel, or gas tube to gas block. And note, if everything is correct in the receiver extension and its parts, then when you pull the charging handle all the way back, the face of the bolt should stop 1/8"~1/4" in front of the back of the ejection port window edge, and the last inch of pull on the charging handle, should be the same tension as the middle of the pull. As for Gold mine of brass in the upper, its coming from burs on the extractor, both on the end of claws, as well as edges of rim relief channels. Hence extractor is rotating on case rim with bolt as it goes to unlock, and these burs are what is causing all the case rim scrappings. So extractor out of bolt, use small jewlers fine to remove any end of claw burs and leave the center section of the claw sharp,  same with ends of rim relief channel on extractor,  Check bottom of rim relief edge wall against bolt face to make sure it not proud of bolt face when installed, and check the bolt face to make sure no burs on either the slot edge for extractor, or burs on the ejector channel as well. If burs on the ejector, then it will need to be removed to clean up it burs.  And a little super black cold bluing on the de-bured parts,and now one will know you touch it.  As for barrel extension, before you clean the barrel, just take a look to see if inside ends of feed ramps are rough, and just need to be knocked down with a round file, to remove burs there could be causing scrapping of the case and bullet on loading.  And the last one, do not use Hoppes gun solvent to clean the barrel. It leaves behind a nasty resudue that when combine with CLP (what you should be using to lightly lube the upper receiver bearing parts) that will cause problems with spent case extraction, and even worse as the rig heats up. So on barrel, something like Sweets to clean the copper out of the bore fast, push patches chamber to muzzle until they come out dry, then switch to CLP with chamber brush to clean out chamber, and again pushing dry patches chamber to muzzle until they come out dry (Qtips for barrel extension void area). Even with the chamber and bore dry from dry patches, will still be enough thin layer of CLP on the metal for short term storage of the rifle. |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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Originally Posted By K5FAL: Thanks Dano523. I do appreciate it. You gave me a lot to go through but at least I have a path, now. Btw, magazines were Brownells, Okay, and D&H, all with MagPul followers. They've worked in other ARs? |
I sell firearms produced by the finest child labor in the world, be it Filipino, Muslim, Mormon, Arizonan, or Texan.
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Originally Posted By K5FAL: Btw, magazines were Brownells, Okay, and D&H, all with MagPul followers. If mags are clean, and recovering correctly, then can weed them out, and not need to figure out if problem is mags not retained high enough in mag well, or if other problem with bolt not making it past the back of round in the mag, for a clean strip of the round. Also, do not use mag as either hold point (can use front of mag well itself), or as bi-pod off the bent. This can end up with canting the bottom of the mag forward in the well, dipping down the back of the mag down enough that bolt can over run the rim of the top round even with the round flush against the bottom of the feed lip. As for new followers, was new springs path of the math if rebuilding the mags, or were the follower just upgrades to the mags to go to anti tilt followers instead? The other one that does come to mind, is when done loading the mag/before it goes into the mag well, make sure to rasp the back of the mag off your hand, or something a little more solid, so the entire round stack has all the case rims tight against the back wall of the mag. When firing the rifle, the recoil of the rig is going to keep all the rounds with the rims tight against the back wall, but you want to them start there to being with. |
Posted By PlaymoreMinds:
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
'Twas not the <cough> sweet and innocent <cough> PlaymoreMinds...
<---skips away in frilly skirts to Candyland, leaving gutters and snorkels FAR behind.
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