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Hi as most of you know who are in the gun community a bunch of AR 70/90 kits came into the country and theirs still no barrels or receivers in production. Since I cant find anything I decided that I'm just going to make my own barrel and I've found the measurements from a guy on reddit who lives in Italy. https://imgur.com/gallery/WUtxuAP https://imgur.com/gallery/1ydhDUS As I was getting the measurements a curiosity ran through my head, how do you mathematically figure out the proper diameter of the gas port hole for the gas block in the barrel? Much help will be appreciated!
So my mind wandered off the other day and I started thinking about bolt carriers, recoil springs and caliber conversions. I feel kind of ignorant for not getting this completely straight, but I'm wondering if I'm missing something. Let's say you'd have an AR-style rifle chambered in .308, and you'd convert it to .223 with a swap of the bolt head and the upper receiver. Let's ignore the magazine issue for this discussion. I'd imagine that the optimal bolt carrier velocity is the same regardless of cartridge (within some reasonable limit). Thus it should be perfectly possible to compensate for the new cartridge only by changing the gas port location or size, and leaving the same bolt carrier mass, the same bolt head mass, the same recoil spring and buffer in there. For some reason I've always had it in my head that a larger cartridge requires a heavier bolt carrier, but I just realized that that's not right. A larger cartridge requires more space on the bolt face, more space in the receiver, and a sturdier lockup. This tends to lead to a heavier bolt carrier group, but there is no need for a heavier bolt carrier per se. Is my understanding correct? Of course there is less volume to work with when running a gas system on a .223 versus having a larger cartridge, but it should be perfectly possible to fiddle with the gas port size and location to compensate. I could also imagine the larger surface area of the larger cartridges to increase friction during primary extraction, but the difference between different calibers should be negligible compared to the difference between dirty ammo and slightly oily ammo. The Saiga rifles use the same bolt carrier and virtually the same bolt for all of the difference cartridges. The Knights Armament SR-25 uses the same springs and buffer as the M16a2 (although they have a heavier carrier and had some issues) The DPMS genII small frame .308 rifles use the same buffers and springs as the 5.56 rifles. Bonus: Check out this thread from arfcom on bolt carrier velocity https://www.ar15.com/forums/general/for_AR_fans_and_engineering_nerds__I_calculated_the_bolt_carrier_velocity_profile_for_an_AR_10/5-1150725/
I found a bunch of my chemical engineering texts that I had PDFs for. I put them on my Google drive, so if anybody is interested, here's a few links. Let me know of if these links actually work. I've been reading through my Reactor Chemistry text when I have downtime at work. Glad I finally am getting around to reading it. Introduction to Engineering Ethics Elements of Chemical Reaction Engineering, fourth edition Fundamentals of Heat and Mass Transfer Numerical Methods for Engineers Thomas Calculus Early Transcendentals Quantum Chemistry
I've posted this on SomethingAwful before, but here's a repost for those of you who haven't given Lowtax tenbux. Warning: it's very long. The Swedish original is called JA 37: pilot och system and is a transcript of a witness seminar held at the Stockholm Museum of Technology in 2007, with a lot of old geezers who had worked on the development of both the Viggen and other Saab aircraft. A very brief glossary: - FMV is the Defense Materiel Administration, which was (and is) the government authority responsible for buying and developing all kinds of equipment for the Swedish armed forces. At the time when the Viggen was being developed, FMV still had a lot of engineers in house, which was considered important since it was thought at that time that in order to buy or develop a good system you had to know how it worked. - SRA is Svenska Radioaktiebolaget (Swedish Radio Company). Acquired by Ericsson in 1983. - LM Ericsson is just Ericsson. The name comes from the full formal name of the company, "Telefonaktiebolaget L M Ericsson", which in turn is named after its founder Lars Magnus Ericsson. - JA 37 is the fighter version of the Viggen. - AJ 37 is the strike version, which predates the fighter version by about ten years (entered service around 1970; the JA 37 around 1980). - 35, or aircraft 35 is the Draken. - 37, or aircraft 37 is the Viggen airframe in general. - 39, or aircraft 39, or JAS 39 is the Gripen. My comments are in parentheses. Please ask away if there's anything that seems unclear.