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Posted: 2/26/2009 7:48:07 PM EDT
| I am just curious about headspacing. I have been looking into it and trying to understand it better, but if you put on a barrel and throwin a bcg and the headspace is a no go, or doesnt line up. How do you and what do you adjust? I've never built an upper but I just got a deal on all the tools to do so, so I'm starting to think about building one just for a project. If anyone has a link or site to visit that might explain this to me better, please hook me up. Thanks |
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I just built 3 uppers for the first time ever. New barrels, new bolts. I just put it all together and shot them at the range. No headspace checking, no nothing.
You can't adjust headspacing, other than to switch out bolts and barrels until it all works out - OR you could have a gunsmith ream out the barrel extension....but, that's just something i've read. My advice? Put it together, load a round and make sure the BCG closes on the round. If so, fire away. If it blows up - then try a different bolt! |
| I'm sure thats what I'd do anyway, I figured if everything was in spec and your torque everything right putting it together you shouldnt have a problem, I just didnt know if there was something you were supposed to tweak if the headspace did work out or what. Thanks |
| The headspace is set when the barrel extension is put on. Once the barrel extension is on the barrel is perminantly mated to that extension because the gas port is drilled based on the extensions orientation. Some barrel makers that make drop in barrels have you send them your bolt to headspace the new barrel correctly. Others send their new barrels with a bolt they were headspaced on as a standard practice. Still others headspace to book values and assume your bolt is in spec. If you go with one of the latter headspace gauges are around $20. Checking it with a gauge may ease your mind. As others have said if you do not have a fit their is little you can do other than trying another bolt. This is especially true with chrome lined barrels as the chamber is chrome lined as well and reaming it deeper would screw the lining. |
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I thought I read it somewhere on this sight.
The military only checks headspace when fitting a used barrel with a used bolt, if both are new or even just one is new, they don't consider it necessary to check the headspace. They check headspace once a year with a "field" gauge, on rifles that fire thousands of round a year, and almost never find one with dangerous headspacing, NOR does the military have any problem with weapons blowing up or anything else you can attribute to headspace. The manufacturers that include a "matched" bolt with their barrel, are supplying ultra-match barrels where everything is built to the closest most exact tolerance in a search for the greatest precision and accuracy. You don't need that tight of tolerance even if you are building a standard rifle, only if your building some SUPER accurate for matchs rifle. The way the AR is designed and built, the headspace will easily be in tolerance just correctly assembling the parts. It can't hurt to check headspace, but if the parts are new, its extremely unlikely it will be out of tolerance, let alone being way past tolerance in the UNSAFE range. Of course, with the mad rush on, people have noticed poor Quality Control in some of the parts making it into the field, you never know, so checking headspace might be a good idea. Like stated, the only thing that can be done if headspace is out of range is swap out the parts, unless its too small, then a gun smith can ream the chamber a little deeper. You can't reem a Chrome Lined bore, you're stuck with the chamber at its dimensions or destroy it trying to change them. |
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