strange load question

[rdsii64]

currently my thunder stick likes 42.5 grains of IMR 4064, federal 210 match primers and topped with a 168 grain sierra match king. (Not sure how fast its going) If I substitute the 168 grain for a 155 grain and use the same amount of powder will the accuracy get better or worse. the barrel is 24" with a 1 in 12 twist.

What I am trying to do is use the lighter bullet with the same amount of powder to reach paper a bit further.

 

[nwcook]

Here's some load data I got directly from Berger for their 155 and 168 VLD's
168 Grain IMR 4064 38.5 2450 42.6 2688 99.60%
155/155.5 Grain IMR 4064 40 2529 44.5 2800 103.20%

42.5 gr looks like too much powder. I'd start lower with the 155 then work up. As with any gun/load combo you'll have to test. The biggest difference in the bullets that would affect accuracy is BC difference. I"m guessing you have a 1/12 twist which is fine for those two bullets.

I've found that I can shoot anything from 35 to 65gr bullets in my .223s with the same accuracy level but the amount of powder and speed changes. Each bullet weight has a sweet spot of powder that delivers the most accuracy. In my .223 the powder charges differ by 1.5 gr from lightest to heaviest.

So you need to test with the new bullet and start out with a load at the lower end of the chart and work up...That's my 2cents.

 

[BHP9]

currently my thunder stick likes 42.5 grains of IMR 4064, federal 210 match primers and topped with a 168 grain sierra match king. (Not sure how fast its going) If I substitute the 168 grain for a 155 grain and use the same amount of powder will the accuracy get better or worse. the barrel is 24" with a 1 in 12 twist.

What I am trying to do is use the lighter bullet with the same amount of powder to reach paper a bit further.

I just check the Sierra Manual.

The 168 is running about 2650fps. Substituting for the 155 will give you about 2700fps.

 

[Michael Eichele]

It really will depend on your rifle as far as if accuracy will be better or worse or the same. The same powder with a lighter bullet will increase the velocity but not as much as most think. Get out and try it!

If you HAVE to have the same amount of powder and want much more velocity, you WILL have to go with a faster powder. Otherwise you will be stuck with a little bit more speed.