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OnlySlightlyCrazy

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  1. OnlySlightlyCrazy

    Aerospace and Ordnance discussion/news.

    My naive response to that is that the Target Detection Device needs to be as far forward as is practical in order to keep your warhead on target when it fuzes and detonates. (At 25kft a Mach 2 missile will pass the entire length of an F-4 Phantom in .06 seconds, which is before you address the fact that the target is moving and you need time for your continuous rod to get on target.) This is a shared configuration with the AIM-7, also a continuous rod warhead missile. Given that the R-27 is a 1980s era missile, it's also possible that the autopilot is electromechanical, not digital, and therefore cannot be trivially removed from the seeker via cable. All this is, of course, speculation.
  2. OnlySlightlyCrazy

    Aerospace and Ordnance discussion/news.

    I should probably clarify what is the grognard's opinions - and these are opinions, he hasn't seen any actual design documents on the R-27/AA-10 - and what are my own assumptions working off of what he posited. Grognard (almost verbatim): The [R-27...] was designed as something that would counter the AIM-7F missile and would have better maneuverability and expanded F-Pole over the Sparrow. The missile is much larger than Sparrow, particularly the longer range variants. The stuff he's seen says that the AA-10 has Canard control. I guess you could take your choice whether its Canard or Mid-body wing control. In any event, the control fins are place closer to mid-body than to the nose. These mid-body control finds need to be larger to generate maneuvers because the moment arm between the center-of-pressure and center-of-gravity is much smaller than for true canard or tail control. The sparrow also has large wings for this reason. Given the large size of the control surfaces, he suspects that the designers were trying to provide “wing-like” surface for long range flight profiles that are quoted. The higher aspect surfaces are of higher aspect ratio, and that in turn provides an improved lift-to-drag ratio on lifting surfaces. This is the only missile he can recall that has control surfaces extended out past the tail fins. The longer (and narrower) control surfaces would concentrate the dynamic loading such that the individual surfaces would have the center of pressure closer to the control hinge axis. This means the surfaces can be rotated with less torque than something like the AIM-7. As such, the control surface actuators would require less power to operate and would most likely respond faster while still maintaining sufficient force to affect the body rotation during maneuvering. He thinks the drawback of this design is that the wings would interfere with conventional launch rail systems, and would not fit into internal weapons bays. This may be why you don’t see a lot of this design; however, from an aerodynamic perspective, he thinks the long, narrower fins are more efficient both in reducing drag and in minimizing control torque requirement. OnlySlightlyCrazy: One of the leading factors in a missile's RMax is it's battery life - many missiles can aerodynamically hit targets much further than their battery can last out to. Thus, having more efficient control surfaces on a missile desiring long range makes sense. As to why the fins are midbody - that's the swappable nosecone bit that Colli shared. That image also explains the forward angle on the midbody fins; you want your fins to be as large as possible since they're midbody, and you want them as far forward as you can get them without intruding into the autopilot or Target Detection Device sections. Thus, having it swept forward means you get a wider fin farther forward, and get to not intrude into other necessary components. That forward sweep is frankly the only usual part of the fin - combining a forward sweep with a conventional fin geometry is what gets you the axe-body. I'm happy to take a crack at further questions myself, or forward them to said grognard before he retires and or dies.
  3. OnlySlightlyCrazy

    Bash the F-35 thred.

    An F-35B has crashed near Marine Corps Air Station Beaufort, South Carolina. Pilot safely ejected, no clue as to cause yet. Airframe appears to be a complete loss given the size of the smoke plume.
  4. OnlySlightlyCrazy

    Designing A Rifle From Scratch(ish)

    I'm rather perplexed that I hadn't noticed that before. Ah well, it is a good day to learn!
  5. OnlySlightlyCrazy

    Designing A Rifle From Scratch(ish)

    Huh. Yeah perhaps I shouldn't have written my thoughts right before going to bed. My understanding of the appeal of multi-lug rotating bolt systems was that they offer a much more consistent lockup due primarily to the number of lugs involved, so that in theory an AR-10 would have a more consistent lockup than a Garand, or possibly in some odd world we could compare the descendants of those weapons. Thus, to my inexperienced eye, moving to fewer larger locking lugs seems like it could introduce inconsistency into the lockup, leading to a reduction in the precision of the weapon. That would be a limitation of the magazine, correct? The SCAR has it's action spring (or maybe it's called the return spring? I don't study bad rifles other than the AR-15) hanging out behind the bolt carrier group and occupying that space in the receiver, with a single spring as shown. I'm curious how you will design your action spring, whether you'll use a single spring in line with the bolt ala SCAR, an AR-18 two-spring assembly, or something novel.
  6. OnlySlightlyCrazy

    Designing A Rifle From Scratch(ish)

    I promised I would provide feedback at some point, but my brain is slow and timid. My chief thoughts are as follows. 1. The arrangement of the bolt is one of the most peculiar aspects of the weapon. Your design certainly appears supported by sound technical reasoning regarding interplay with the rounds in the magazine. My concern is that a reduction in the number of bolt lugs will correspondingly degrade the precision of the weapon. Of course, this is in the context of military ammunition, and yet more worrisome, military shooters. Further, it is certainly reasonable to accept some loss of precision to gain increase reliability of the weapon during feeding, given your starting premise. I would, in short, like to see the data. 2. The retention of the AR-15 FCG components is an interesting move. I always thought it odd that fewer companies exploited reusing existing components in this fashion. If I'm understanding correctly, it would also be easy to move towards a "cassette" style of trigger pack, which is of growing popularity with the AR-15 market. 3. Your decision to devise your own magazine is admirable, and you certainly seem to have succeeded. My friend is curious if you can handle longer ogive, possibly ~66gr range EPR style 5.56 projectiles in the magazines. I'm not sold on drums, as their weight and bulk are disconcerting, but the ability to have them is never a bad thing. 4. I have no idea how you're going to solve the action-spring issue. I'm eager to see to what degree you can balance the forces acting on the bolt. Given you're trying to be unique, I wonder to what degree you'll end up matching the SCAR or other AR-18 descendants. Given the shape of the space you're working with, I do have my predicitions. (They mostly involve it being real goose hours, so I shan't share.)
  7. OnlySlightlyCrazy

    Designing A Rifle From Scratch(ish)

    It's worth noting that many manufacturers, even some well regarded, choose to include M-Lok only on those surfaces and angles they deem most useful, using other (presumably cheaper or stronger) cutouts in other locations. Imo, this artificially limits the modularity of the rifle, which is one of the AR-15's many claims to fame. From what little I know, the ability of the rail to hold zero is - for aluminum or steel rails - determined mostly by the length and rigidity of the barrel nut. Flex of the rail itself is, if memory serves, less of a concern. That said, post 2005 any new rifle design does need to bear in mind that the laser, not the optic, is the primary aiming device for 50% of the life of the weapon, if not more, so paying additional attention or accepting additional weight in service of that fact is wise.
  8. OnlySlightlyCrazy

    Designing A Rifle From Scratch(ish)

    What would you say was the minimum necessary amount of additional weight to soldier-proof the M16A1? Is it mostly the furniture, or were additional steps such as the new lower receiver and the accursed barrel truly needed?
  9. OnlySlightlyCrazy

    Gun Science Library

    Sturgeon wanted me to share some files for him since he's on mobile, figured I'd get off my lazy bum and actually do it. Exterior Ballistics Charts Prepared by Coxe and Beugless. PPC Case Design and Development including work done by Palmisano and Pawlak. Let me know if these can't be viewed.
  10. OnlySlightlyCrazy

    Documents Repository: Small Arms

    Freshman outing here, I go by James elsewhere. I stole the entirety of Sturgeon's library last night, so I figured it would be kind of me to reciprocate. PDF warning for all of these. Sensitivity Study of Rifle Gas Systems Comparison of a Theoretical and Experimental Study of the Gas System in the M16A1 Rifle The Gas Flow in Gas Operated Weapons Enjoy!
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