High velocity readings

[Abolt]

I have a 300 wsm with a bartlein 26" barrel. I tested some Hornady 150g btsp and h4350. When I loaded these up I used the data from the Hornady book, after looking tonight I noticed they are 3 grains heavier than my other books I have. I'm wondering if my chronograph could be off or if anyone has any other ideas.

My load:
Norma 300 wsm case
Hornady 150g btsp
Col .010 from lands
Federal gm215m
H4350 67g, 68g, 69g, 70g, 71g.

Here are the velocitys:

67g: avg: 3184 sd: 7.54
3181
3176
3190
3192

68g: avg: 3339 sd: 30.74
3303
3351
3375
3329

69g: avg: 3386 sd: 13.95
3374
3396
3374
3400

70g: avg: 3370 sd: 11.15
3361
3364
3370
3386

71g: avg: 3465 sd: 8.85
3475
3471
3459
3457

Looking at these numbers velocity is considerably higher than book values. The 71g load is pushing RUM numbers. Here is a picture of one primer from each group. 67g bottom left and 71 top right, cannot get the picture to rotate. Also the 100 yd group of the 71g. .377" first 3 and .54" overall. It seems to have potential.

 

[Abolt]

Picture of group

 

[Engineering101]

Looks to me you are only slightly faster than Hornady book values since you are running a 26" barrel and their data is based on a 24" barrel. Primers don't appear to be very flat either. The only problem I see is your bullet choice. You are going to cut something in half running that bullet that fast. Were I you I would switch to a 200 grain ELD-X running around 2,900 fps. At least then you will have something left to eat - assuming that this is a hunting load you are working on.

 

[dok7mm]

71 grs appear to be a "bridge too far". Primer is flat and looks like its trying to flow on one side. I would reshoot 68-69.5 in .3 increments, or at least .5 charges. See what you find. Go at least to a 180 gr. Good Luck