I had a request for a BBT even shorter and lighter than the 1.5 caliber long version on the previous page.... When I looked at the requirements (a .30 cal that was only 0.375" long), I quickly realized that the only practical way would be to simply remove the boattail and go with a flat base.... Here is the result....The length would be almost exactly as requested in .30 cal, and it would weigh 59 gr. as a HP and 63 gr. as a FN.... Trying to incorporate a boattail in such a short slug would not leave enough bearing area to keep the slug straight in the bore, IMO.... Something in between in length (~ 1.4 cal.) would be able to use a short gas-check style stub and stay within the 8 degree convergening cone recommended by Miles....Bob
Here is the improved BBT design for slugs that are 1.5 callibers long.... I have used all the improvements listed in the OP, within the limitations required for such a short slug.... Notice that the boattail has all but disappeared.... Once again, the weights for other calibers are shown in blue....Note that these calibers are typical "airgun" calibers instead of the PB calibers I used above.... as these slugs in the smaller sizes (up to .30 cal) would be more likely to be used in airgun barrels.... The slug weights in .357 and .457 caliber are much more typical of what we might use for those.... Once again, the twist rate is proportional to the caliber.... so the .30 cal slug would be optimal in a 26" twist.... Bob
Give this company a try, he is firearm friendly and might do one or two just to make a video. No idea what he would charge but worth a quick email to ask him about this work.Might even get him to make a couple of molds (moulds). He could make a good buck on molds if he had the machine time to make them, the shortage is killing everyone.{edit} I sent him a message from the contact form on his website, hopefully he gets the message. That said, I need to get a shop set up at home, I could probably get little stuff like this made in the little space I have available.