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  1. Miles_M

    Revolutionary Umarex Komplete NCR PCP Air Rifle Launched Today

    It is a nice idea but, as said, it is something which will be used while a novelty and then put in the back of the cupboard. Pity sales are driven by claimed speeds on the box. If the power was wound down to say 12FPE you would get more shots which would help the cost factor. You still couldn't...
  2. Miles_M

    12 foot pound .177 is very underrated

    In the right situations, you can get more than 12FPE by getting a Fire Arms Certificate. You need to show you have somewhere to shoot, such as pest control on farm land which is rated for FAC. However, I have seen many posts from pest controllers who have given up their FAC rifles and just use...
  3. Miles_M

    Spin Drift

    Spiralling and spin drift are only remotely linked as they are both related to gyroscopic stability factor but in different ways. Spiralling, which is random and not exactly repeatable, is caused by increases in gyroscopic stability giving large increases in yaw wave length, coupled with poor...
  4. Miles_M

    Spin Drift

    Well, I do say it does not make much difference. It is only at long range that you may see it, but even then it will depend on your zero range. The bigger the difference between your zero range and your target range, the more likely you are to notice a it.
  5. Miles_M

    Spin Drift

    Stabilization is produced by moments about the centre of gravity (CG), not forces. The base drag on a pellet is high, but it has no, or close to no, moment arm about the CG, so it cannot produce a stabilizing moment about the CG. You could have an infinite force acting through the CG, but...
  6. Miles_M

    Spin Drift

    Naval shells do not fall flat on the surface, to do that they would require gross gyroscopic over stability which would make them unusable in higher elevation firings as they would end up going sideways. I know, I have seen it happen when something was fired at the wrong elevation. Also, I was...
  7. Miles_M

    Spin Drift

    First point, pellets are not, never have been and hopefully never will be drag stabilized. For the true aerodynamic explanation of pellet aerodynamics, see this thread. Ballistic Theory - Correcting What You Have Been Told About Pellet Aerodynamic Stability Secondly, I said in the post that this...
  8. Miles_M

    The Daystate Guide To Airgun Barrels – Part Three

    That is interesting since the ballistic modelling (which apparently according to experts does not work on pellets ;) ) suggests that for ranges of 100 yards the optimum twist rate is around 30-32 inches per turn, as opposed to something around 20 inches at 25-50 yards. If other longer ranges are...
  9. Miles_M

    The Daystate Guide To Airgun Barrels – Part Three

    While ballistic theory will not give exact results, (ballistic modelling can under certain specific conditions) practical testing can only give the correct results if the test results are interpreted correctly based on known ballistic characteristics. I have seen dozens of statements being made...
  10. Miles_M

    Let’s Take A First Look At Airgun Barrel Twist Rates

    I am rather puzzled by this as all other studies which have been carried out over the last hundred years or so show that at higher altitudes, high temperatures with thin air, projectiles require lower twist rates for the same stability compared to low altitudes with cold temperatures. The...
  11. Miles_M

    Ballistic Theory Twist Rate Related Posts

    This one is very technical and not easy to follow. It will not improve your shooting, but it may help to understand the effects some pellet faults can have on your group sizes and how fliers can occur. It is the last of the pellet based posts looking at the effects of spin rates for pellets with...
  12. Miles_M

    Airgun Barrel Twist Rate – Does It Matter?

    The problem with just about all of the stability calculators, including Bob McCoy's McGyro program, is that they are much simplified systems, which assume a solid shot and use aerodynamic approximations which become inaccurate at certain speeds. Hollow point slugs, many with hollow bases, are...
  13. Miles_M

    Let’s Take A First Look At Airgun Barrel Twist Rates

    Twist rates will normally get less as calibre increases. Due to the changes in the moments of inertia and the aerodynamic moments with bullet or pellet size, if you use the same twist rate for different calibres, you will either end up with less spin stability than optimum for the small calibres...
  14. Miles_M

    Airgun Barrel Twist Rate – Does It Matter?

    This might sound silly, but have you tried a slower twist rate at a lower speed?
  15. Miles_M

    Ballistic Theory Twist Rate Related Posts

    This is a short follow up to the previous post, after a request to repeat the exercise for .177 pellets. I have also briefly compared the two calibres. Following on from the post on the effects of an offset CG on a .22 pellet, I have had time to do a little work on the same make .177 sized...
  16. Miles_M

    Ballistic Theory Twist Rate Related Posts

    This was the first of the 12 FPE threads I created years ago for UK forums. They tend to follow on from each other, so I will post them all in this thread in the order they were created, or some may not make sense. It may take me a while to do it. There are plenty of videos on YouTube which...
  17. Miles_M

    Airgun Barrel Twist Rate – Does It Matter?

    Twist rates are a subject I have carried out many individual studies on over the years. There are a number of posts on various forums, mostly though for 12FPE speeds and ranges up to 50 metres. At the speeds and ranges looked at, twist rates in the 16 to 22 inches per turn tend to come out best...
  18. Miles_M

    Wind forecast

    One of the ranges we used for small arms testing is actually in one of the windiest places in the UK, just what you don't want for test firings. Spent many a day sitting around waiting for the wind to drop to merely gale force.
  19. Miles_M

    Wind forecast

    This nearly always happens with our weather forecasts on the news. But then, with our changeable weather, I am not surprised. When we started using predicted local weather on our firing trials rather than our own weather balloons, we had a new forecast every 2 hours and they could change...
  20. Miles_M

    Wind forecast

    It may be the best time for pellet testing, as the pellet which is best in calm conditions may well be unusable when the wind blows.
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