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Posted: 4/15/2006 1:18:33 PM EDT
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I recently purchased (from DPMS)a lower parts kit and what I thought was a complete assembled upper. My friend gave me a stripped lower and I assembled it in about an hour. The upper is not assembled. Can I assemble the upper without worry of improper head space setting or does DPMS have the head space set when they ship the parts out? If I can assemble the upper without having to worry about head space I could save myself $65-$75 to pay a gunsmith to do it. Thanks in advance for any advice. On a side note me and a buddy ordered parts from DPMS on Jan. 13 and the parts did not arrive until Apr. 11. When we ordered we asked if the kit telescope stock and they told us yes. When the parts arrived I got a regular stock. After calling them several times and being promised that they would be shipped on three different occasions it took approx. 13 weeks to receive the parts. While waiting for a reply to this question I found this on-line @ http://groups.msn.com/TheMarylandAR15ShootersSite/maintenacefaq.msnw Q: How do I Headspace an AR-15? A: Courtesy of LTC Santose 99% of any "concern" about headspacing is based on a lack of knowledge about what headspace is and does. Unless you take a grinder to the bolt, or fire several thousand rounds of ammunition on AUTO, you can't induce dangerous headspace. The Army, which fires a zillion rounds a year has one (1) gage. Gage, headspace, field. That's it. If you buy commercial barrels and bolts from Bushmaster or Colt's you don't need to worry -- or even THINK -- about headspace. Unless you've fired several thousand rounds of ammunition you don't need to worry -- or even THINK -- about headspace other than an ANNUAL check with the field gage. Reserve units only do it every two years. If the bolt closes on the field gage you fit a new bolt. If it closes you fit a new barrel and use the OLD bolt. If that fails use a new bolt and new barrel. No GO or NO-GO checking, just FIELD. There's no concern about a NEW bolt in an old barrel. Heck it's going to be larger -- no wear -- than the old bolt and there will be less headspace. Do NOT use commercial gages. Is this accurate and a trustworthy source? |
| If you have the proper tools and mechanical aptitude to assemble the upper receiver then it shouldn’t be a problem. With a new barrel and new bolt "I" personally don’t feel the need to check headspacing, some may differ with me on that though. If the upper receiver does not have the barrel installed then I can’t see how the upper receiver was ever headspaced. You may want to contact DPMS personally on that one. |
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Headspace isn't affected by putting the barrel on the upper. It's measured between the bolt face and chamber, so you won't make the headspace over or under by simply assembling it. Personally I've never fired an upper that I built without checking headspace. I agree that it would be a very rare (but not impossible) occurence to have improper headspace using facory new parts, but it's a very quick and easy way to get some peace of mind, and prevent any possible malfunctions or worse. ETA: Calling DPMS is good advice. I would assemble the upper yourself, then have the headspace checked by the gunsmith...they shouldn't charge that much for a simple headspace check. Or, perhaps DPMS can recommend/sell you the proper gauges and you can check it yourself. There's a TON of .223/5.56 go/no go gauges on the market, I think that's where a lot of people get confused as well. |
True, but if the upper and barrel were never mated but are separate pieces sitting in a box, then I doubt that they were ever headspaced. Would not make sense to assemble them, check headspacing, then disassemble. |
I would hope that if all the parts in the kit came from DPMS, they would check headspace before shipping it out just for safety reasons. You can check headspace without putting the barrel on the receiver, if I was selling complete kits like that, I know I would. 
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Cheaper to buy the gages than pay a gunsmith to check it. www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=119964 |
FRom that page:
Edited to correct myself: Isn't there a difference in SAAMI spec and 5.56mm? With the majority of AR's being 5.56mm and SAAMI reserved for match rifles? From the Oly web site:
www.olyarms.com/?rootView=page&page=oabarrels |
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The Santose headspace comment is correct, and Lt. Col Santose is a knowledgeable, reliable person. His "Santose Improved Battlefield Zero" sight in method is legend. As far as the barrel and bolt being separate pieces, true. But the bolts are checke to be within tolerance, and so are the barrels. If both are in spec, then together they are, too. Even with "stacked tolerances" you won't induce a dangerous headspace situation. Headspace is not going to be a problem with new good quality parts. |
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