'Gunnut69': I've used 37 grains of IMR-4895 with 180gr. Sierra and 185gr. Lapua bullets with very good accuracy and no signs of excessive pressure. I neck-sized my cases by backing off the F.L. Sizing Die at least one turn. Bullets were only seated enough to allow functioning through my Krag's Magazine. The Cartridges fed without a problem. I used regular W-W Large Rifle primers and Remington Brass.

I also used 130gr. Sierra bullets with 42 grains of IMR-4895. The accuracy was good, but, feeding of cartridges was more problematic.

FWIW - I've had good to fair accuracy results with 147gr. (W-W) G.I. bullets in different Krags. (Some rifles like them better than others). Feeding has not been so smooth, with some bullet noses hanging up on the barrel breech. I was using W-W 748 (40 grains), only because I have 7 pounds of it.

IMHO - IMR 4895 is a wonderful versatile powder. 36 grains now appears maximum with 150gr. jacketed projectiles. (I would Neck-size about 2/3 of the long .30-40 case neck and seat 150gr. bullets as far out as practical).

Parashooter supplied some good up-to-date data, with pressures. (I personally would use the 36 grains of IMR-4895 as a maximum).

(My previous guide was my older Hornady Manual and others. It appears some loads, I have used, could now be risky).

I've always been a conservative, low pressure, 'starting-loads' kind of guy. Data is subject to change. Loads I've used and have experience with, during the past 35 years, although showing no evidence of excess pressure, need to be reviewed.

FWIW, IMR-4064 is also a very good versatile powder to use with the lighter bullets.  I've loaded Hornady 165 gr BTSP bullets with 38 grains of the 4064 with very good results.

Be aware however, not all Krags like the same food.  What works in one Krag may not work as well in another, and although some shooters will tout their load as the end all/be all... ultimately, you should find what load works best for you.  For some of us, that means trial and error. 

Another point since this is your first Krag:  Not all Krags feed spritzer bullets well.  mine do, but only if the bullet is crimped.  I've tried the 150 FMJBT once, but I was not happy with the feed VS RN in my competition rifle so I went back to my ole standard 220gr RN.  You'll have to play with it to know if those 150s will feed reliably in your Krag, but don't be discouraged.  It may come down to crimp vs no crimp, or OAL, or some other minor issue.

Good luck, and let us know how she does.