In answer to the OP question, I have not tried this load yet, but do intend to soon. I will chronograph the load as I usually do just because I like testing it personally, and will post results after doing so.
As far as the cost of BB ammo............
Yes it is pricey, however I don't think the ammo was ever designed for shooting 100 rounds a week at paper or steel targets. I carry the BB ammo in my Chief's Special and in my M65, and although I will shoot a dozen or so of my carry loads a year just to stay familiar with them, I do not shoot hundreds of rounds of the stuff at a time. That being the case, the cost per round is of little importance here, as my life is worth the 20 or 30 bucks a year it costs me. For routine practice, I will hand load - not trying to duplicate the BB ammo, but to get close enough to the "feel" of the ammo to make it viable practice ammo.
The BB +P 38 Spl. and .357 loading's are SO FAR SUPERIOR to what is otherwise available that to me the cost of shooting a few rounds per year is negligible. Anyone who has not tried the stuff has to shoot it for themselves to see what all the rage is about:
1) accuracy
2) actual chronograph verification - out of YOUR carry gun
3) reliability
4) controlability in YOUR gun
I realize one size will never fit all, but the 5 or 6 loading's have shot and tested so far has really impressed me enough to use BB ammo as my go to carry load weather in my M60-7 or M65 - whether I am in the streets or in the woods. Just my opinion of course.
Regards,
Chief38