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Posted: 5/5/2015 8:35:39 PM EDT
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I have been reading and reading and watching videos on building an AR15. This head space thing is crazy. Some say it does not matter, some say it is very important and still some say it doesn't matter because you cannot change it even if it is not within spec. This is probably an age old question on these boards but what gives? I mean as a first time builder who are you supposed to believe or what are you supposed to believe.
If you buy a barrel with the barrel extension wouldn't the head space already be set? Or does the bolt change the head space? Can the head space be corrected or not? Sorry if this all sounds stupid or if this is repeat stuff on this forum bt you read so many contradictions it is just ridiculous. Any help or advice would be greatly appreciated. |
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Basically, if the parts are milspec, the headspace will be fine. Lot's of guys get a headspace guage just to check it. That makes them feel better. The reality is that if the headspace is off, there isn't anything you can really do about it. There's nothing you can adjust. The best way to not have to concern yourself with it is to get the barrel and the bolt carrier group from the same place. Then, they are factory headspaced. So, you buy an Aero Precision barrel, and an Aero Precision BCG - or the two from any other company that makes them. The rifles I have put together with milspec parts have never had a problem with headspace.
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| If the headspace is to little the bolt won't go completely into battery and possibly over pressure if it does go. If the headspace is to much then you could be firing an unsafe weapon with dangerous consequences. It's worth the $50 for the two gauges for piece of mind. The only adjustment is to try a new bolt or barrel. Any reputable company will happily exchange them for you if they are not in spec, even if they aren't from the same company. |
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Quoted:
If the headspace is to little the bolt won't go completely into battery and possibly over pressure if it does go. If the headspace is to much then you could be firing an unsafe weapon with dangerous consequences. It's worth the $50 for the two gauges for piece of mind. The only adjustment is to try a new bolt or barrel. Any reputable company will happily exchange them for you if they are not in spec, even if they aren't from the same company. I firmly agree with this.... I would not shoot an AR that I have built without checking the head space. The people that say you should be ok are correct Inan essence. As long as the head space is ok then your ok. If the head space is not good, you could end up with a KB. Not worth the risk IMO. YMMV... |
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Quoted:
Basically, if the parts are milspec, the headspace will be fine. Lot's of guys get a headspace guage just to check it. That makes them feel better. The reality is that if the headspace is off, there isn't anything you can really do about it. There's nothing you can adjust. The best way to not have to concern yourself with it is to get the barrel and the bolt carrier group from the same place. Then, they are factory headspaced. So, you buy an Aero Precision barrel, and an Aero Precision BCG - or the two from any other company that makes them. The rifles I have put together with milspec parts have never had a problem with headspace. Not necessarily correct. There is no guarantee that headspace is ever checked just because a company sells both barrels and bolts. I would certainly bet in most cases that they do not. |
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Quoted:
Basically, if the parts are milspec, the headspace will be fine. Lot's of guys get a headspace guage just to check it. That makes them feel better. The reality is that if the headspace is off, there isn't anything you can really do about it. There's nothing you can adjust. The best way to not have to concern yourself with it is to get the barrel and the bolt carrier group from the same place. Then, they are factory headspaced. So, you buy an Aero Precision barrel, and an Aero Precision BCG - or the two from any other company that makes them. The rifles I have put together with milspec parts have never had a problem with headspace. Bad advise. Sticking your head in the sand and pretending like it is not a even possibility is not the way to go. If you build enough of them you will run across barrel/bolt combinations that will not headspace correctly. It has happened to me twice. bolt would not close on go gauge. If it does not headspace correctly, try another barrel/bolt combination rather than trying to mess with the barrel extension. |
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Bad advise.
Sticking your head in the sand and pretending like it is not a even possibility is not the way to go. If you build enough of them you will run across barrel/bolt combinations that will not headspace correctly. It has happened to me twice. bolt would not close on go gauge. If it does not headspace correctly, try another barrel/bolt combination rather than trying to mess with the barrel extension. So that is pretty much it, if the headspace is not correct you have to try another barrel or another bolt? Do most of these manufactures selling AR items online take them back with no hassle? Seems to me this could be a big hassle if you had incorrect headspace to deal with??? |
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The information that a 223 REM / 5.56 MM chamber with insufficient headspace will not close on a cartridge is not right. Commerical manufacturers that produce brass at the minimum specification from the bolt-face to the 0.330 datum line would have brass at this area measuring 1.4596". This is 0.005" thousandths of an inch shorter than the military specification from the bolt-face to the 0.330" datum for a new barrel that has been high pressure tested (HPT) or 1.4646".
Which a barrel that hasn't been checked for headspace that chambers cartridges that measures at this minimum specification can still have headspace that is out of specification. Which as long as ammunition is fired that meets this minimum specification you'll never know you even have a barrel that is out-of-specification for headspace. The problem is cases in this area can measure from 1.4596" to 1.4666", and still be within specification. This is when you can run into problems. As for headspace, the second and third drawing below shows how headspace is measured for 223 REM / 5.56 MM chambers. If you subtract the bolt dimension in the red box (0.156") from the barrel dimension in the red box (1.6206"); you'll have a headspace measuring 1.4646", which is the military specification for minimum headspace for a new barrel that has been high pressure tested (HPT). As for which headspace gauge measurements to acquire to check headspace, these are the gauges I'd use; Go Gauge 1.4636" (bolt closes) No-Go Gauge 1.4666" (bolt doesn't close) Field Gauge 1.4736" (bolt doesn't close) (this gauge can be purchased later on for checking headspace yearly) 
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Quoted:
So that is pretty much it, if the headspace is not correct you have to try another barrel or another bolt? Do most of these manufactures selling AR items online take them back with no hassle? Seems to me this could be a big hassle if you had incorrect headspace to deal with??? Quoted:
Bad advise.
Sticking your head in the sand and pretending like it is not a even possibility is not the way to go. If you build enough of them you will run across barrel/bolt combinations that will not headspace correctly. It has happened to me twice. bolt would not close on go gauge. If it does not headspace correctly, try another barrel/bolt combination rather than trying to mess with the barrel extension. So that is pretty much it, if the headspace is not correct you have to try another barrel or another bolt? Do most of these manufactures selling AR items online take them back with no hassle? Seems to me this could be a big hassle if you had incorrect headspace to deal with??? Yup, the good ones will. That's why I deal with Brownells whenever possible. They will take back anything, for any reason. However those dealing with bottom feeder parts from Joe's gun parts (fictitious) on Amazon to save 5 bucks should be prepared for the consequences should something go pear shaped. |
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