Terminal velocity & your thoughts…

Forums Pellets, Projectiles, Slugs, & Ammo Terminal velocity & your thoughts…

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    dunderklumpten
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    Newbie here. Just saw a very impressive 100 yard group on this forum done at a really quick muzzle velocity and it made me think back to my old clay target shooting days.

    Quite often at competitions, you would here someone claim “ I use such n such a brand coz they are f%-‘$”n hauling arse (mandatory use of bad language slang in Australia) at 1350 feet per second.!!!” Little round lead balls are not particularly high in ballistic co-efficient and in reality, by the time the shot intercepts the clay pigeon, it’s actually only doing a handful of feet per second faster than my far more comfortable on the shoulder after 2 days of shooting 1200 FPS handloads.  The target is fragile. If you are spot on target, it will still turn to powder.  

    I even once had a go at Olympic trench shooting (and those targets come out at about double the speed). I was hopeless at 14/25 success, but what was funny was one of my reloads was dodgy.  The crap powder I was using at the time had a habit of jamming & only a fraction of the powder fell into the case.  When I fired the sound was just ‘wrong’. I knew it, the other shooters knew it and guess what? I hit the target & it still broke, so so much for velocity.

    Has anyone ever sat a chrono at the target end and compared muzzle velocities to the velocity at the target?  How much faster is that really unaerodynamic pellet doing at 100 yards when compared to a muzzle velocity increase of 100 feet per second? Remember, drag increases at the square of speed.

    Love to hear your thoughts.

    Dave

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    JCD
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    https://www.airgunsofarizona.com/Calcs.html

    about half way down the page

    but yes, what you describe is done occasionally. often to calculate one's specific ballistic coefficient.

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    dunderklumpten
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    JCD

    https://www.airgunsofarizona.com/Calcs.html

    about half way down the page

    but yes, what you describe is done occasionally. often to calculate one's specific ballistic coefficient.

    That is an awesome link. I will be tinkering with it in the future.

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    Odoyle
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    I used to until the far distance chrony got shot using an old school type chrony.

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    dunderklumpten
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    Odoyle

    I used to until the far distance chrony got shot using an old school type chrony.

    Ouch! That sucks.

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    GeneT
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    JCD

    <snip> often to calculate one's specific ballistic coefficient.

    And that's really what ballistic coefficient is – how quickly a projectile loses velocity all else being equal.  A key to remember is that ballistic coefficient is directly proportional to weight – so a heavier projectile will always lose velocity more slowly than a lighter one of the same shape.  I don't think any experienced hunter would argue for a lighter bullet at higher velocity for best terminal performance.

    GsT

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    Bob_O
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    JungleShooter
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    dunderklumpten

    Has anyone ever sat a chrono at the target end and compared muzzle velocities to the velocity at the target?  How much faster is that really unaerodynamic pellet doing at 100 yards when compared to a muzzle velocity increase of 100 feet per second? Remember, drag increases at the square of speed.

    Love to hear your thoughts.

    Dave

     

    OK, I'll bite.

    Here're the calculations. ๐Ÿ˜Š 

     

    ๐Ÿ”ถPellets loose about 50fps of the 100fps lead.

    Slugs loose about 25fps of the 100fps lead.

     

    ๐Ÿ”ถThe wind drift is only marginally affected by a higher MV. Actually, if the MV falls into the transonic region the drag increases thus increasing wind drift, so going from 900MV to 1000MV isn't really advantageous in this example (maybe shooting out to 200 or 300y might change the picture).

     

    ๐Ÿ”ถA ranging error of 1 yard at 100y will obviously affect the POI. However, a 100fps higher MV does not seem to make much of a difference at all.

     

    ๐Ÿ”ถHowever, a 100fps MV increase requires between 7 and 9 FPE more muzzle energy, so a 30FPE gun would need to produce c. 38FPE. And that's indeed a large increase (27%). I imagine that results in a large decrease in shot count! And in a large increase in loudness!

     

    So, unless my gun will shoot with more precision, I maybe should stay with 30FPE….

    Thanks for asking the question.  Now I know….!  ๐Ÿ‘ ๐Ÿ˜Š 

    Matthias

     

     

     

     

     

     

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    dunderklumpten
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    Well this is all very interesting figures I'm reading. Actually I'm surprised that the pellets don't lose as much speed as I thought they would.

    I also totally agree with the argument that there has to be a big drop in group size to warrant the price paid in noise & shots per fill. Noise is important here coz we can't fit moderators, and I've always been one to seek accuracy over velocity in all my various shooting hobbies over the years.

    Thanks all for some great info.

     

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    vmaxpro
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    I hunt, alot. I push for the max fpe, best accuracy, and balance the effeciency as best as I can tune it. Pellets nose dive the bc when pushed fast. BUT, Ive seen one hole groups at 40 yards and then take a dump at 100 shooting slower. The last gun I tuned was purpose built for slugs and just happened to be deadly with pellets as a bonus ๐Ÿ‘. I’ll put a chrono this weekend at the muzzle and at 100 shooting 1065fps and then again at 890 fps using jsb’s. Calculators are great, but nothing better than real life data. 

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    dunderklumpten
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    vmaxpro

    I hunt, alot. I push for the max fpe, best accuracy, and balance the effeciency as best as I can tune it. Pellets nose dive the bc when pushed fast. BUT, Ive seen one hole groups at 40 yards and then take a dump at 100 shooting slower. The last gun I tuned was purpose built for slugs and just happened to be deadly with pellets as a bonus ๐Ÿ‘. I’ll put a chrono this weekend at the muzzle and at 100 shooting 1065fps and then again at 890 fps using jsb’s. Calculators are great, but nothing better than real life data. 

    Vmaxpro, hi there. It was actually your target that got me thinking.  It’s great that your groups shrunk in size with speed (and yes, i’m  Impressed with the accuracy you are achieving with the velocity).  Like you mentioned, you hunt a lot and you also said you wouldn’t bother heading down this path if punching paper.

    Please don’t take my thoughts on the matter the wrong way.  I totally agree that hunting and target work are 2 different environments. If I fire one 10 shot magazine when hunting in a day then that’s a whole lot of shooting, so who cares about shot count in that circumstance.  If that velocity is what it takes to maintain accuracy at longer distances, and shot count doesn’t matter (typically it wouldn’t when hunting) then it’s all good.  What are you hunting for? Just curious 

    I’m hunting bunnies out to say 60 yards with a 25 cal pellet so yeah I’m more inclined to seek accuracy over energy.  Lucky for you that you have found both.

     Btw, I’m running my pellets flat out as well as that’s when they group well at 50 metres, but my gun maxes at 900 FPS. However, if my group size halved at 850, then I would detune.

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