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Posted: 11/23/2008 6:00:58 AM EDT
| I'm a FNG and i'm building my First. I bought a upper from a guy at work for $150 and he had it for some yrs and never used it, which he had bought from another person. My question is... how do i check the head space? |
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Why, with a headspace gage of course.
First you need to have an idea of what chamber dimensions your barrel has been given. Brownells offers gages in commercial .223 as well as 5.56 Nato dimensions. Normally headspace gages come in a set of three, a GO gage, a NO GO gage, and a FIELD gage. http://www.brownells.com If you want to be rough and ready, they also offer a basic field gage that will tell you whether the rifle is safe to shoot or not. You hand chamber a headspace gage like a regular cartridge using your thumbs to push forward on the carrier assembly. Some gages require that you remove the ejector and extractor assemblies prior to checking the dimensions but most new made gages allow these parts to remain in place during the check. Ask someone who knows or read the instructions prior to attempting to use the gage if you are uncertain. A GO Gage will allow the bolt to fully close which tells you there is a minimum safe headspace in the rifle chamber. A NO GO Gage should not allow the bolt to fully close, though using a commercial .223 NO GO gage in a 5.56 NATO dimension chamber usually means this gage will allow the bolt to close. Consequently trying to use a 5.56 NATO GO Gage in a commercial .223 chamber usually ends up with the bolt not fully closing. Closing on a NO GO indicates that headspace is at near maximum dimensions and it would be wise to have some corrective surgury done on the rifle in the near future. The Basic Colt Field gage will tell you whether there is sufficient maximum headspace to safely fire the rifle regardless of the chamber dimensions the rifle may have been given and this basic gage is what many, many folks use to check a rifle for safe tolerence. If a rifle bolt closes on any FIELD Gage DO NOT attempt to fire the rifle. Closing up on the maximum dimension FIELD gage indicates the rifles headspace is far in excess to be considered safe. HTH |
| I am curious then if for the most part headspace is not a HUGE concern with an AR, some barrel makers will sell you a bolt that is already headspaced to the barrel. My estimation is that some are charging a lot for doing so and some are charging a few dollars over the cost of a new bolt. |
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Quoted:
I am curious then if for the most part headspace is not a HUGE concern with an AR, some barrel makers will sell you a bolt that is already headspaced to the barrel. My estimation is that some are charging a lot for doing so and some are charging a few dollars over the cost of a new bolt. I think you're correct. Many people aren't well versed in how ARs work and don't know how insensitive they are to headspace issues. That makes 'em easily impressed by the "for an extra $190 we'll also sell you a bolt custom headspaced to THIS barrel!!!!! offers. Not what I'd call good business practices... |
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Quoted:
I'm a FNG and i'm building my First. I bought a upper from a guy at work for $150 and he had it for some yrs and never used it, which he had bought from another person. My question is... how do i check the head space? Does this upper come with a bolt? What does the guy say about it? If it's the same bolt he got with the upper and he's "never used it," there should be no issue whatsoever. But checking the headspace is a good idea on any "unknown quantity" AR upper/bolt combination, simply to ensure that you're getting quality assemblies and not something that someone threw together without regard for quality or fit. |
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