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Sturgeon's House


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About Miroslav

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  1. You send your nerdiest engineer to go do some theoretical calculations while you stay in the workshop and mount the barrel in a press drill and put a small hole in the barrel. If you can't get the rifle to function properly, then you put the barrel back into the press drill and use a larger drill bit. Repeat until the rifle works properly. You'll be done before the nerdy engineer. I too look forward to a theoretical answer, but in practice, fluid dynamics are very complex and I'm sure that most gas operated firearms developed during the 20th century had a lot of empirical iterative developm
  2. And also, I thought I was quite the wannabe who keeps diving deeping into knowledge about military equipment that I'll never work with, but the Japanese can hardly own a knife without asking permission for it first. They are so irrelevant to gun culture, and gun culture should be so irrelevant to them. Yet here we are. There is Japanese fan fiction about Obobob.
  3. What the fuck? I thought I was pretty obscure who keeps checking this thread for content, and the obscure guns in it, but there is actually some guy out there who is making anime schoolgirl artwork with these weird prototypes. What the fuck? This world is so strange. By the way, I mostly lurk in this thread, but I'm really grateful to you guys who keep filling it with content. Especially the русский stuff.
  4. 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 fo
  5. If you look at the difference in manufacturing costs, I think Sturgeon does have a good point. The tubing or operating rods or whatever needed for the gas system are rarely very expensive parts. I'd guess that the difference in costs associated to the bolt head and barrel extension is larger than the entire cost of small parts for the gas system. I could be wrong. Also, there's the development hurdle of designing a new rifle. If you're trying to invent a roller delayed blowback, as far as I understand, you'd have to experiment with different angles on pieces that are made from hardened stee
  6. Well the FAMAS isn't a bad design. Given that they were going to make their own production line from the ground up, I wouldn't say that it's an irrationally expensive design either. On the modern US commercial firearms market there has been some efforts to make semi-locked or locked bolts for pistol caliber carbines and submachineguns. This lowers felt recoil, ameliorates performance with suppressors and with some larger pistol calibers. SIG has a gas operated, rotating bolt design, but I wouldn't say that it's completely clear that the SIG design is leaps and bounds better than the CMMG radia
  7. There are a bunch of semi automatic hunting rifles that have solved this problem. The reason for placing the gas system below the barrel is that it fits nicely into the handguard. This makes the rifle keep a traditional and slim profile. In general, they are much lighter than for example the M1 Garand, but they have a lot of small parts and are kind of messy to disassemble. This is afforded by the designers because they have access to modern manufacturing methods, and their customers rarely have to take the rifle apart in a hurry, or in the dark, or in the rain. One positive side effect of thi
  8. I still admire Amerika for generating so much disposable income among its citizens that they feel like they can afford sinking so much of it into such futile projects.
  9. I'm sorry, my sarcasm wasn't coming through. This spring is (according to the designer) what keeps the bolt from rotating in the bolt carrier, before it has moved all the way forward to the chamber. https://ibb.co/K5Xs4zV <a href="https://ibb.co/K5Xs4zV"><img src="https://i.ibb.co/mRGyZFh/APED.jpg" alt="APED" border="0"></a> I don't think they'll ever get anywhere with this.
  10. Don't get me wrong. I'm an ignorant fool. I'm not an entrepreneur. It takes courage to go into the unknown and take a chance. I still think this anti-pre-engagement mechanism is worthy of some appreciative attention. I know you all read or write for tfb but here's the link. No time link cuz the whole interview is worth watching. I really wonder how he funded this thing. I really love how he's passionate, but how will he ever compete with a guy like serbu? https://www.thefirearmblog.com/blog/2020/11/18/the-50-bmg-ak-project-as-told-by-brandon-th
  11. Well, as long as you have a set of premises to keep your definition of "normal circumstances", your formula holds up very well as a general pointer. I still think the factor "3" is high. There are so many different kinds of tried and tested receiver shortening "crazy BS" design elements availible to a designer that perhaps the formula could be further specified to: If: R2>3*(C2-C1)+R1 Then: designer is lazy What do you mean by bolt extension distance? I'm guessing the difference in how far the bolt lugs protrude from the bolt carrier as the bolt is u
  12. I could buy the first two increments, but I don't think you should count having the spring in the forend as "crazy BS", and if it's in the forend (or there's just enough space in the carrier to stuff it in there anyway) you don't have to extend the receiver to fit the spring. Also you counted the bolt length twice. And you could have the hammer extend over the rear end of the magazine (or any bolt hold open device), which would save you from having to extend the firing pin all the way from the chamber to behind the rear of the magazine. I think the SU-16 has that configuration, but I'm not sur
  13. Hey Sturgeon, you can't just drop an authoritative statement like that formula and not back it up. Please show us how you came to the number three. I'm genuinely curious. Having this extremely specialized hobby as well, I have a notepad at home with calculations made to the same end. Writing from on top of the loo at the office, I would have guessed at 2 rather than 3. Also, you must need a lot of premises to be valid for it to be true, mainly that the receiver was designed for optimization with regards to overall length. There are a lot of CAD models of the scar availible online.
  14. Yeah that looks like quite the distance. Is it meant to reduce the angle the cartridge has to tilt to get from the double stack to the center position?
  15. On bolt arrangement: I've been thinking I should go with a six lug bolt, with the lugs arranged like the seven lug bolt on an AR-15. This is inspired by the recessed lug that some manufacturer (I've forgotten which one) uses on the lug opposed to the extractor. As far as I can calculate, this setup is plenty strong. Bolt carrier should look kind of like a .308 AR carrier cut off behind the firing pin and instead of a gas key it has a protrusion where the op rod/piston hits it. I have some vain dreams of spending a ton of money to have a prototype of this rifle built. As I'm based i
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