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Posted: 3/6/2010 6:24:51 PM EDT
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i am building an ar15 and i atached the bolt to the upper but when i place a round in the chamber the bolt wont close all the way.
I am able to get the bolt to close if i tap the cartridge down a little my question is if i file a little off the lugs on the back of the bolt or use sandpaper to enlarge the chamber area in the barrel extensio enough to get it the round to seat correctly and the bolt to close |
you are kidding right??????? If not.step away from the parts and call a gunsmith............Had to say that....
1. Check to make sure the gas tube isn't bent. 2. Are you checking with the ejector in the bolt, if yes it will be hard to close by hand. 3.Under no circumstances should you file or sand on the locking lugs or the chamber......if it is a new barrel....99.999999999999% probability nothing is wrong....if it us a used barrel...have the barrel and bolt checked with a headspace guage...it will require removing the extractor and ejector form the bolt. |
Ignore the brilliant minds above who were clearly blessed to be born with full knowledge of gunsmithing. Not all of us are so lucky 
Modifying the locking interface of the chamber and bolt lugs is a Very Bad Thing ®. There were a couple good suggestions above regarding the gas tube and ejector. Another thing to consider is this: are you loading the test round via a magazine, or are you placing it in the chamber by hand and making the extractor snap over the cartridge rim? |
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The gas tube will definitely cause issues if the end is slightly buggered, or if the bolt carrier key is dinged. I dropped a BCG on the ground while in the USMC and had to follow a very pissed off DI to the armory to get it fixed!
Also, is everything sloppy wet with lube? If it's a new build or bolt install everything should be swimming in lube. AR's love lube. Finally, are you letting the bolt fly home from the fully retracted position? Will the forward assist finish chambering the round? You could be running too dry, you could have damaged magazine feed lips slowing down the bolt too much while stripping the round, your chamber could be tight (is it a match barrel?), or the ammo could be out of spec. Are you using reloads? "Riding" the bolt forward is a no no as well. It can make it hard to strip a round off the mag, and it can make it hard for the extractor to ride up and over the cartridge rim as the bolt goes into battery. |
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Is the ejector in the bolt? That shouldn't be an issue unless it's extremely sticky... Or am I missing something? You need to remove the ejector and extractor from the bolt while checking head space. I know this needs to be done when using gauges, but I'm not sure if it's an issue while using a round. |
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Is the ejector in the bolt? That shouldn't be an issue unless it's extremely sticky... Or am I missing something? You need to remove the ejector and extractor from the bolt while checking head space. I know this needs to be done when using gauges, but I'm not sure if it's an issue while using a round. I'll try again. Huh? 458 |
| well i dont have it fully assambled yet i am trying to piece it together as i get the money the gas tube is not installed yet and the problem im having is by inserting the round by hand it doesnt fit into the chamber fully but both parts are new so im not sure i got the barrel from a friend along with a few other parts but they were all new im not out any money on the parts so im trying to fix it for as cheap as possible without paying for a chamber reamer |
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If it will chamber when you let the BCG fly forward chambering the cartridge and eject the cartridge when you pull back on the charging handle you are GTG.
It can be a little sticky and work itself out in a few rounds (20 or less). Otherwise, evaluate your case sizing procedure and adjust as necessary. If that's not it borrow a reamer and take a 1/4 turn at a time with it until the rifle functions. You really should do this using a GO gauge. |
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well i dont have it fully assambled yet i am trying to piece it together as i get the money the gas tube is not installed yet and the problem im having is by inserting the round by hand it doesnt fit into the chamber fully but both parts are new so im not sure i got the barrel from a friend along with a few other parts but they were all new im not out any money on the parts so im trying to fix it for as cheap as possible without paying for a chamber reamer Chad, its sounding like you may not know how ask what you want to ask (no insult, gun terms take a lot of learning). Its douptful that you actually have a headspace issue with a new barrel. From what I read, your rifle is not assembled & you are dealing with just the barreled upper, bolt & bolt carrier. You've placed a cartridge in the chamber and are attempting to close the bolt on said round with finger pressure but are experiancing resistance. Possibly too much. And you are wondering if your chamber is too tight because the cartridge doesn't just drop in and the bolt close right up. Is this correct? If yes, have you: completely cleaned the chamber? inserted clean, dry, NEW factory cartridge (no reloads!!) fully into the chamber with your finger? (you should be able to push it into the chamber with just finger tip pressure until it is all the way in and less than about 1/8" of it poking out of the chamber/bbl face) If you can insert the cartridge into the chamber, make sure the upper & bolt/carrier are well lubed (inside and out), hold the upper pointing striaght down, retract the bolt fully to the rear (without pulling the charg handle back) and drop it letting gravity shut it on the cartridge. It should close all the way (fully lock up) or need just a little thumb pressure/bolt assist to make it finish hopping over the case rim & lock up. Remember, you are having to push the extractor over the cartridge rim, collaps the ejector, and cam the bolt closed with the mass of the bolt carrier. If all the parts are new, you are also having to push the bolt piston back into the carrier & it may also be dragging quite a bit too. All of this = resistance and right now it sounds like you are trying to do this without a recoil spring or buffer to help the bolt close. Normally, if you can close the bolt with thumb pressure on the rear of the carrier (albit firm) and retract the bolt & eject the cartridge, you don't really have a serious headspace issue. Just a new gun that needs to be taken out & shot. However, If you have trouble closing the bolt on a cartridge and then have serious trouble unlocking the bolt & extracting the cartridge, then you may have a headspace issue that needs to be properly checked out with gauges. Proper means stripping the bolt of ejector & extractor or having a notched, rimless gauge that only interacts with the bolt face & chamber. MLG |
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Is the ejector in the bolt? That shouldn't be an issue unless it's extremely sticky... Or am I missing something? You need to remove the ejector and extractor from the bolt while checking head space. I know this needs to be done when using gauges, but I'm not sure if it's an issue while using a round. I'll try again. Huh? 458 This is what I'm referring to: Quoted:
However, If you have trouble closing the bolt on a cartridge and then have serious trouble unlocking the bolt & extracting the cartridge, then you may have a headspace issue that needs to be properly checked out with gauges. Proper means stripping the bolt of ejector & extractor or having a notched, rimless gauge that only interacts with the bolt face & chamber. MLG |
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