GTA
All Springer/NP/PCP Air Gun Discussion General => Projectiles => Boolit and Pellet Casting => Topic started by: rsterne on November 09, 2019, 05:57:12 PM
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I have drawn up a scaled down version of the .257-65 BBT and posted the drawing in a thread at NOE.... Here is the drawing.... Note that the twist rates on the drawings are from the Kolbe Twist Calculator, and are convervative for my Bob's Boattails, they always seem to work in a slower twist....
(https://i378.photobucket.com/albums/oo221/rsterne/NOE%20Bobs%20Boattails/NOE%20224%20cal%2040%20gr%20HP_zps2ohzkln6.jpg) (http://s378.photobucket.com/user/rsterne/media/NOE%20Bobs%20Boattails/NOE%20224%20cal%2040%20gr%20HP_zps2ohzkln6.jpg.html)
Based on the success of the .257 version, this should work great in a 14" twist TJ's barrel.... and it shouldn't be too much of a trick to drive it at 950 fps in a powerful PCP.... I would have Al make the tooling slightly undersize, so that NOE could also make a .217 cal version, with the boattail shortened (which increases the stability) to work in Hatsan or Marauder mags.... that would be 35 gr. as a HP....
(https://i378.photobucket.com/albums/oo221/rsterne/NOE%20Bobs%20Boattails/NOE%20217%20cal%2035%20gr%20HP_zps426fkncd.jpg) (http://s378.photobucket.com/user/rsterne/media/NOE%20Bobs%20Boattails/NOE%20217%20cal%2035%20gr%20HP_zps426fkncd.jpg.html)
The question is, would it work in the twist rate of any of the .22 cal airgun barrels around.... I would hope it would work in a 16" twist.... ::)
If you are interested in either version, please post at the NOE Forum in the following thread....
http://noebulletmolds.com/smf/index.php/topic,1127.0.html (http://noebulletmolds.com/smf/index.php/topic,1127.0.html)
Bob