Yes, Yes, and Yes!
I don't have my logs right in front of me, but I believe I have some Speer data I got directly from them for Longshot, I'll dig around for that. But in the mean time you can use jacketed data for another bullet of same weight, or similar weight.
Hodgdon has data for a Sierra 125 gr. FMJ, as follows:
Longshot= 4.7 grs. - 5.7 grs.
I've used this data for Gold Dots and other JHP's, which the Gold Dot is in the same data class as a jacketed bullet. this load is not a sweet little powder puff, it's a full performing load. But Long Shot is so easy to work up, in that it has such a large charge table, it isn't spikey or temperamental. It does perform more consistently and accurately when worked up to the upper end though. So in this respect, Longshot is best suited for full house loads, and it doesn't do well when loaded at the bottom end, it needs those top end operating pressures to attain an efficient and complete burn.
GS