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Thread: 270 chrono results

  1. #1

    270 chrono results

    Done some chronograph testing with my home loads at the weekend and was pleasently surprised at the results especially as my 270 has a 20 inch barrel and caused me many a sleepless night ! First loads were 130grn gameking with 57.3 grns of RL19 and averaged 2856 fps. Next up were the 110grn vmax with 52.5grns of Viht N150 and they averaged out at 3196 fps, all fairly consistant as well. Brass used for the 130s was hornady and brass used for the 110s was federal all loads used cci 200 primers. Going to try some norma brass and cci br primers next to see if that improves consistancy.

  2. #2
    Quote Originally Posted by 243 fallow View Post
    Done some chronograph testing with my home loads at the weekend and was pleasently surprised at the results especially as my 270 has a 20 inch barrel and caused me many a sleepless night ! First loads were 130grn gameking with 57.3 grns of RL19 and averaged 2856 fps. Next up were the 110grn vmax with 52.5grns of Viht N150 and they averaged out at 3196 fps, all fairly consistant as well. Brass used for the 130s was hornady and brass used for the 110s was federal all loads used cci 200 primers. Going to try some norma brass and cci br primers next to see if that improves consistancy.
    Nice work. Of course, using a chrono has it's downsides. You start worrying about statistical things like was the number of shots fired across the screens adequate for an accurate assessment? Standard Deviation.... More sleepless nights. I finally got the point where a 10 shot string was minimum as a 'sampler' to see if a load was worth continuing with and a 20 (sometimes 30 shot) string for the final analysis. I keep thinking that I want to run 50 shot strings of centerfire ammo but I'm too lazy.~Muir

  3. #3
    Its funny thing reloading even if you think you have the perfect load you still look for ways to improve, that was the first time ive used a chronograph and have to say it was nice to see the velocity in the region of what i expected especially the 130grn bullets. Im looking to develop a 150grn load and see how that performs.

  4. #4
    Quote Originally Posted by 243 fallow View Post
    Its funny thing reloading even if you think you have the perfect load you still look for ways to improve, that was the first time ive used a chronograph and have to say it was nice to see the velocity in the region of what i expected especially the 130grn bullets. Im looking to develop a 150grn load and see how that performs.
    You were smart to invest in one. A reloader without one is flying blind. Want to have some fun? Set up your chrono at the normal distance (10 or 15 ft) and fire ten shots. Then jog the chrono exactly 50M (at least) down range and fire another 10 shots. Record you averages. Note elevation, temp, and if possible, barometric pressure. Then find any number of free, on-line programs that will take the averages you have gotten at the muzzle and then down range, and convert them to an actual ballistic coefficient. Then you can plug that number into the same calculator and come up with some really fine drop charts tuned to your rifle, accurate at your location, with the actual ballistic coefficient you are getting at those speeds under those conditions. (Having two chrono's saves you a walk.)~Muir

  5. #5
    I like that idea Muir, but I know this guy and its my chrono....... There's no way he is shooting at it 50 yards away, I hardly trust him to put the bullets through the vanes at 10 feet

  6. #6
    Quote Originally Posted by Wingers243 View Post
    I like that idea Muir, but I know this guy and its my chrono....... There's no way he is shooting at it 50 yards away, I hardly trust him to put the bullets through the vanes at 10 feet
    LOL! Ok, but then my eyebrows will climb a notch if you ever post about shooting one of those pint-sized UK garden deer through the heart at 150 yards! ~Muir

  7. #7

  8. #8
    Quote Originally Posted by Muir View Post
    You were smart to invest in one. A reloader without one is flying blind. Want to have some fun? Set up your chrono at the normal distance (10 or 15 ft) and fire ten shots. Then jog the chrono exactly 50M (at least) down range and fire another 10 shots. Record you averages. Note elevation, temp, and if possible, barometric pressure. Then find any number of free, on-line programs that will take the averages you have gotten at the muzzle and then down range, and convert them to an actual ballistic coefficient. Then you can plug that number into the same calculator and come up with some really fine drop charts tuned to your rifle, accurate at your location, with the actual ballistic coefficient you are getting at those speeds under those conditions. (Having two chrono's saves you a walk.)~Muir
    Yep I done this but put chrono at 300 yards with a couple of sandbags in front there was a difference in the bc values the bullet manufacture publish. JBM do a good online program for working out bc.

  9. #9
    Quote Originally Posted by gr1ffer View Post
    Yep I done this but put chrono at 300 yards with a couple of sandbags in front there was a difference in the bc values the bullet manufacture publish. JBM do a good online program for working out bc.
    There is always a difference in values of BC from the manufacturer. People seldom realize that the BC of a bullet changes with velocity and all environmental elements. I shoot a 33 grain V-Max from my Hornet designed for the Remington 22WMR cartridge. At 2150 fps WMR speeds the BC is around .142. When fired from my Hornet at 3200 it's down to around .100 iirc. A big difference. I shot in the Rifle Silhouette Nationals at the NRA Whittington Center in Raton, New Mexico one year. All my ballistics were done at 5000 ft elevation and I shot the matches at 7500 ft elevation. (?) I was young then and totally surprised when my first round at sight in about fell off the target. Lesson learned.~Muir

  10. #10
    Quote Originally Posted by Wingers243 View Post
    I like that idea Muir, but I know this guy and its my chrono....... There's no way he is shooting at it 50 yards away, I hardly trust him to put the bullets through the vanes at 10 feet
    I know him too. I've seen his shooting too I wouldn't trust him with it stuck to the end of the barrel. If it's your your chrono you got no chance in getting it back either !

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