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Posted: 4/18/2012 5:05:18 AM EDT
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OK newbie question, so patience with ignorance,
I want to buy a complete upper but I do not want the front sight. These are substantially cheaper than with just gas blocks installed, but I want to add Troy folding sights. I know the front sights can be removed, I will not grind them down. I believe they are pinned, so I can use a punch to get them out. So my question is this: I want to get an upper with front sight that is cheap and I remove the front sight, and I want to put a low profile gas block so a rail can go over it. I have seen gas block that are screwed (i think) to the barrel. I want to know if they can be pinned like the front sight originally was. I am concerned about any rotation. Also I am pretty good with hand tools and common sense, for someone that has never installed a gas block is this over my head. I watched a video at Brownell's and they say just be careful to align it with gas block hole. Guys let me know if I am correct with all I have said. And if screwed on gas block vs pinned is a big deal. Thanks in advance. |
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Alot of people run gas blocks that are screwed in place, and the hold up just fine. A gas block can be pinned and places like adco can do it for you. If you punch the pins out of an FSB, you can't just slap a new gas block on using the existing pin holes so just keep that in mind. You have a couple ways you could go about what you want to achieve. 1. You can buy an upper from someone that already has a rail and low profile gas block on it. 2. You can buy an upper with a standard upper and cut down the FSB and then install a rail. 3. Build your own upper from scratch exactly as you want it. 2 and 3 would both require some tools and pulling the barrel off depending on what parts you are working with.
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| Yes you can easily swap out the gas block for one you want. You should get a clamp type, especially if it will be covered by a rail. You will have to post specific parts you want for further help. I am not sure how much will be saved by buying a complete upper then changing both the gas block and adding a free float hand guard…. Many free float hand guards use proprietary barrel nuts also. So everything will have to come apart just to go back together. It would be easier to just build it the way you want from the beginning. |
| Yeah I have thought about that. Only problem is I don't know that I have enough knowledge. Especially when I hear about the "head spacing". Keep hearing how important it is to be accurate with that. I am not sure I even understand what head spacing is. Do you need special tool for this? Again, I realize may be dumb questions. Having a hard time finding out what head spacing exactly is and how to make sure it is correct. |
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Quoted: headspace is set at the factory. 99.9999999% of the time it is perfect. If you can screw a 1/4-20 nut onto a screw you can assembly a upper if you spend about 1 hr reading and about 60 bucks in tools. This. You can build and upper with a barrel wrench and upper receiver block, roll pin punches help, and some basic hand tools. I know it looks complex at first, but it really isn't too bad. If you absolutely want to buy a complete upper set up how you want I'd look at BCM or PSA. BCM has a ton of options as far as configuration.
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Ok, so I am still looking for a simple definition,that I can understand, about headspacing. I am considering building out an upper on my own. What areas make up the headspace areas that I would need to watch out for?
In other words if I buy an upper receiver, then barrel, gas block, tube, rails and associated washers/nuts etc. and begin to assemble together, am I worried about headspacing? Is the BCG attachment where headspacing applies? If I know what area is not involved, I would be a lot less skeptical about my skillset. |
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Quoted:
Ok, so I am still looking for a simple definition,that I can understand, about headspacing. I am considering building out an upper on my own. What areas make up the headspace areas that I would need to watch out for? In other words if I buy an upper receiver, then barrel, gas block, tube, rails and associated washers/nuts etc. and begin to assemble together, am I worried about headspacing? Is the BCG attachment where headspacing applies? If I know what area is not involved, I would be a lot less skeptical about my skillset. Headspacing involves the chamber, barrel extension and bolt. Buy a field gauge, read the instructions and check your headspace with that. It's a simple check to verify a safe chamber. I use the Colt II Field Gauge which measures 1.4736" If the bolt closes on this gauge the rifle is considered unsafe to shoot. New Rifle Headspace: 1.4646" to 1.4706" SAMMI headspace gauges to use: 1.465" and 1.470" Unsafe Rifle Headspace: 1.4736" Use the Colt M16/AR15 Field Gauge: 1.4736" or, The US military gauge: 1.4730” |
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Headspace in a nutshell:: The distance between the face of the closed bolt and whatever stops the cartridge from going deeper into the chamber is the headspace. As with all machines there is some tolerance allowed. The .223 or 5.56MM uses the cartridge shoulder as the stop point. A .22LR uses the thickness of the rim, a belted magnum cartridge uses the belt.
The AR-15 uses standardized parts and headspace is set by the shape of the chamber in the barrel and the barrel extension, which is factory-installed on the barrel, and the bolt. These parts almost always fit together correctly. Build with decent parts, and you probably will never have a headspace issue. If you need to spend the money on a set of headspace gauges, they're not too expensive. If you don't reload you may never notice excessive headspace. The brass stretches and expands to fill the empty space. Insufficient headspace can cause chambering and extraction difficulties. |
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Quoted:
Hey great explanation, thanks everybody. Guess I'm on way to building. Nice!! you can't mess up if you use the PROPER TOOLS and follow directions. The tools part could save you some headaches from damaging finishes…. I recommend you buy a barrel/ bolt combo that has been pre checked for head space if you want to be sure it is ok. I didn't though. Like others said nearly 100% of the time as long as parts are in spec the head space will be good. If you have too much head space the bullet casing can stretch too much and fail. |
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Quoted:
Hey great explanation, thanks everybody. Guess I'm on way to building. Many vendors will check the headspace for you if you buy both the barrel and bolt carrier group from them. Rainier Arms checks headspace before they ship. Just one less thing to worry about. Personally I'd compare the prices of the following: Building your own upper with exactly the parts you want. Use the drop-down menu to select which parts you want on the upper with a parts kit Use the drop-down menu to select which parts you want with a fully assembled upper If you do end up removing a fixed front sight then here's a cool low profile gas block that was made for replacing a fixed front sight. this one even has starter holes drilled if you wish to pin it. There are a lot of similar low pro gas blocks made for this purpose. Here is another design |
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