Today I took my newly bedded .270 out with a promising new load I've developed. The idea was to try various seating depths (since I changed the bedding). It's amazing what 0.005" difference in seating depth can make!

The load is a 150g Nosler BT with a healthy charge of IMR 4350

Here were my groups

1) 3.355" OAL - 1.311"
2) 3.350" OAL - 1.113"
3) 3.345" OAL - 0.833"
4) 3.340" OAL - 0.358" , 0.391"
5) 3.335" OAL - 0.523"

I think I have a winner with 3.340". I am going to load 20 of them and see if I can repeat this level of accuracy next weekend. Needless to say I will be a happy camper if I can.

just curious, but isn't( 3.340" ) max OAL? If you are shooting a bolt action rifle, did you try putting any of the longer length cartridges in the magazine?

Yes, 3.340 is the SAAMI Max length for the cartridge. The box magazine will take rounds up to 3.375" (didn't try any longer) in length without a problem. It's not uncommon to have a magazine that will accept rounds considerably over the Max SAAMI length.

Buzz;
Alright! it does sound like you have a winner there! That is some awsome accuracy! I just didn't want you to find out the hard way as I did once by seating them so shallow they wouldn't fit in the magazine! LOL!
I tried some 140gr nosler ballistic tips a couple years ago and they did ok for me but have since gone to sierra 140gr Boat Tails, stay right at 1" or so, and that not to bad for unaltered M70 XTR.
Good luck with those 20!

BUZZ,
OH,OH. Finding out such as this is satisfing but they are also contagious. If you load for another rifle I'll bet you're looking at them now. Welecome to the club. Good luck.