Posted: 2/10/2010 5:07:37 AM EDT
| Does anyone local to Rockland County, NY (or Westchester or Orange or anywhere nearby) have a 5.56 NATO USGI Field Gauge I could borrow to check a new build? I have been trying to find a source for a 5.56 NATO USGI Field Gauge but can't seem to find them anywhere. Any help is appeciated! |
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Thanks! The real reason I want to use a USGI Field Gauge is that they can be use wtihout pulling the ejector from the bolt. I'm tempted to just find a smith who can do a quick check for me and leave it at that. If it is a build with all new parts don't worry about head spacing it. The majority of people don't. |
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Thanks! The real reason I want to use a USGI Field Gauge is that they can be use wtihout pulling the ejector from the bolt. I'm tempted to just find a smith who can do a quick check for me and leave it at that. If it is a build with all new parts don't worry about head spacing it. The majority of people don't. This ^ |
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Thanks! The real reason I want to use a USGI Field Gauge is that they can be use wtihout pulling the ejector from the bolt. I'm tempted to just find a smith who can do a quick check for me and leave it at that. If it is a build with all new parts don't worry about head spacing it. The majority of people don't. This ^ I'm going to have to disagree with this. When building a new rifle you should always check headspace. Every time I replace the bolt I also check for headspace. Midway sells the gauges for pretty cheap. I thought they sold a pack of three (go, no go, and field) but I cant seem to find it right now. Some searching around that section will probably find it. To me I would rather spend the $50 than have a rifle explode in my face (well not exactly explode). Here is a great article on headspacing. You can see the problems that can occur when there is improper headspace. |
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I was under the impression that 5.56 and 2.23 headspace gauges were basically the same a 223 gauge could give incorrect readings in a barrel chambered for 556. I use a .223 headspace guage on my 5.56 rifles. Never had a problem. I am not 100% sure but I think the two guages are very similar. If not exactly the same. I was rereading the above and I wanted to clarify what I said before. IF you order a complete upper the factory should have headspaced everything for you. But if you are building your own upper or switching out a bolt you should check your headspace yourself. 99 out of 100 times the headspace will be fine but why take the chance. |
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Sounds good. I'll pick up the gauges soon and an ejector removal tool. Is there a way to get the ejector out without that tool? here is a decent article. ETA: disregard the rest of the article about cutting the spring. No tools needed but they do make the process easier at times. I compare it to a pivot pin detent installation tool. Can you install without it? yes. Is it a pain in the ass? YES. But for the very limited time you will need one I stick to the manual method. |
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Thanks! The real reason I want to use a USGI Field Gauge is that they can be use wtihout pulling the ejector from the bolt. I'm tempted to just find a smith who can do a quick check for me and leave it at that. If it is a build with all new parts don't worry about head spacing it. The majority of people don't. This ^ I'm going to have to disagree with this. When building a new rifle you should always check headspace. Every time I replace the bolt I also check for headspace. Midway sells the gauges for pretty cheap. I thought they sold a pack of three (go, no go, and field) but I cant seem to find it right now. Some searching around that section will probably find it. To me I would rather spend the $50 than have a rifle explode in my face (well not exactly explode). Here is a great article on headspacing. You can see the problems that can occur when there is improper headspace. I have built 20+ uppers and have yet to have one blow up on my face. The caveat is that I ony buy quality parts from quality sources. If you buy cheap parts from unknown sources, then I will have to agree with you. I only check headspace on AR15s when using used upper receivers, caariers, bolts and barrels. Any other platform such as FALs, AKs etc., I always check headspace. In any case, headspace guages are a good thing to have and it is also a good thing to learn how to use them. |
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Thanks! The real reason I want to use a USGI Field Gauge is that they can be use wtihout pulling the ejector from the bolt. I'm tempted to just find a smith who can do a quick check for me and leave it at that. If it is a build with all new parts don't worry about head spacing it. The majority of people don't. This ^ I'm going to have to disagree with this. When building a new rifle you should always check headspace. Every time I replace the bolt I also check for headspace. Midway sells the gauges for pretty cheap. I thought they sold a pack of three (go, no go, and field) but I cant seem to find it right now. Some searching around that section will probably find it. To me I would rather spend the $50 than have a rifle explode in my face (well not exactly explode). Here is a great article on headspacing. You can see the problems that can occur when there is improper headspace. I have built 20+ uppers and have yet to have one blow up on my face. The caveat is that I ony buy quality parts from quality sources. If you buy cheap parts from unknown sources, then I will have to agree with you. I only check headspace on AR15s when using used upper receivers, caariers, bolts and barrels. Any other platform such as FALs, AKs etc., I always check headspace. In any case, headspace guages are a good thing to have and it is also a good thing to learn how to use them. I said in a later post: "99 out of 100 times the headspace will be fine but why take the chance." I agree with you the number is probably even higher than that when using quality parts. I also said "well not exactly explode" because I never personally seen an AR explode. But I have seen ruptured cases on a very old worn out ARs. Yes I do agree the AR tends to be a platform that eliminates headspace problems naturally. And if I bought a brand new completely assembled upper I wouldnt even bother checking. But if I build my own or use old parts for the $20 (and the 1min it takes to check) im not gonna take the chance. |
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"I've put together one (hundred, thousand, insert various number) of builds and never have had a problem"
But by the grace of God? Never know about the next build, though, as previous ones have nothing to do with the next. 
Using proper chamber gauges is the easiest way to check for "stacking of tolerances". When anything is manufactured there are certain tolerances in that process. The more complex the part or more parts in the assembly the more tolerances are involved. Used parts have greater tolerances because of wear. On average the tolerances more or less cancel out, so the end result (in this case chanber length) falls within safe tolerances (in this case a range of about 0.009"). This is the center region of a statistical bell curve. Rarely all the tolerances add up to a worst case scenario ("stacking") where the chamber ends up out of spec. If manufacturing processes are kept to tighter tolerances, this is less likely to happen staistically, but as one machinist said "all those zeroes past the decimal point cost money". Its more cost effective to produce parts to a less tighter but reasonable tolerance, assemble, and check the final product, throwing out the occasional assembly that lands on the fringes of the bell curve, or just recycling the parts back into the mix where they may be fine with other different sets of parts. The other point is even on "quality" "namebrand" parts, mistakes are made. I have personally seen several in my small circle of AR cronies, occuring in some very well known brands. If you are assembling a barrel, barrel extension, and bolt you as manufacturer are responsible for the end product, in this case the chamber length. |