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Posted: 5/7/2009 10:36:33 AM EDT
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Whats the difference between a 7075T6 Forgings upper made by a USGI contractor (BCM) and say like a noveske upper or an MUR? thanks for the info.
I've also hearde of 4150 and 4140 forgings, and I believe 4150 makes you mil-spec and the infor on the 7075T6 upper says its mil-spec. As you can tell im a little lost haha. |
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4140 & 4150 refer to the barrel steel, not the upper material. 4150 is what is used for military rifles. IIRC the MUR is litteraly cut out of a block of aluminum with a CNC machine, while forged uppers get most of their shape via the forging process (lots of pressure and a set of dies). Uppers & Lowers that are cut from a billet have less dimensional variance than forged, but the forged are supposed to be a bit stronger. Billet cut receivers generally cost more due to all the extra machine time required. |
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Buying parts from quality manufactures you should never have a problem with fitting. From what I've seen most of the billet stuff is held to tighter tolorances so part from the same manufacturer fit like a glove together. ETA: If you'd like I could move this to the Uppers/Lowers/Barrels forum as I think you'll get more responses on the billet stuff there. |
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Quoted: I gotcha, have you experienced or heard of any issues with fitting in forged vs. the billet receivers? I expecting not but im assuming billet are a little easier to get up to dimension that a forged one. just a quick fyi - they are all building from the same set of plans for the important dimensions, so forged vs billet - the fit should be = . this is where the quality of the machining would come in and wouldn't have difference between a billet or forged piece. dimensions are dimension regardless of what material. the ffl manf will buy the raw forging and then the final cutting is done on a cnc machine anyway, so basically all are at the very least finish cnc machined. you are not going to see any raw area in a critical dimension area. this could be done on a manual setup, but for volume, you need the speed of industrial cnc. |
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