Interpreting Results 223 Bolt Action

[bhoeff]

The setup: 223 Remington 700P LTR, 75gr AMax, Lapua Brass, H4895, Wolf primers Dillon 550b, RCBS dies

Round one: 22gr to 24.5gr in half grain increment coal 2.26 100 yards 5 shot groups new brass

Round two: 22gr to 24.5gr in half grain increment coal 2.425 100 yard 5 shot groups Lee Collet Neck sized

Question: How can accuracy improve while standard deviation increase?
Overall velosity was lower at every load on round two and group size smaller.
Is this shooter error?

 

[Kevin Thomas]

bhoeff,

SD and accuracy have virtually nothing to do with one another, at least not at short ranges like this. It'll be a critical issue if we're talking about thousand yard loads, and I'd be a lot more picky even with 600 yard ammo. However, at 100 and 200 yards, I've seen loads that delivered horrendous SDs turn in bug hole groups time after time, without fail.

 

[Trickymissfit]

The setup: 223 Remington 700P LTR, 75gr AMax, Lapua Brass, H4895, Wolf primers Dillon 550b, RCBS dies

Round one: 22gr to 24.5gr in half grain increment coal 2.26 100 yards 5 shot groups new brass

Round two: 22gr to 24.5gr in half grain increment coal 2.425 100 yard 5 shot groups Lee Collet Neck sized

Question: How can accuracy improve while standard deviation increase?
Overall velosity was lower at every load on round two and group size smaller.
Is this shooter error?

drop down to a 55 grain Vmax or a 50 grain bullet, and start all over

 

[Nomosendero]

drop down to a 55 grain Vmax or a 50 grain bullet, and start all over

I agree, unless Rem has came out with a 1-8

 

[bhoeff]

bhoeff,

SD and accuracy have virtually nothing to do with one another, at least not at short ranges like this. It'll be a critical issue if we're talking about thousand yard loads, and I'd be a lot more picky even with 600 yard ammo. However, at 100 and 200 yards, I've seen loads that delivered horrendous SDs turn in bug hole groups time after time, without fail.

Thanks for the reply,
Unfortunately for load tuning 100 is all I have so I try to make groups smaller.

I guess the reason for my question is: With the best 5 shot group at .713 and velocity at avg 2833. Should I A: try to push it faster or B: use a slower powder?

No pressure sign at all. Velocity faster in shorter coal (2.26)

Does velocity correlate directly with pressure?

After I shoot up all of the AMax I will probably start over with 69-70gr but I am determined to learn all that I can about this load in this gun. I want to find the highest BC bullet I can shoot from this gun so that I may begin shooting longer range.

 

[Kevin Thomas]

bhoeff,

Trickymisfit mentioned something that I was taking for granted; that you had sufficient twist to shoot the 75s. That'd be a 1x8, maybe a 1x9", a little bit of wiggle room with a buttoned barrel. Assuming you do, no problem. I edon't think you're going to get a great deal more velocity out of this combination, since 2,850 is flirting with a max load already. A slower powder will likely mean you'll run out of room in the case and probably see lower speeds with what you can get in there. Faster powders could lead to pressure issues. Stick with the 4895, Varget or RL-15 range for heavy bullets like this in the 223. They're your best bet for both speed and accuracy. If you're dealing with a factory barrel, and their typically slower twists, a lighter (shorter) bullet is in order.

Yes there is a relationship between pressures and velocity, but it's not linear by any means and can be deceiving. Seen plenty of instances where adding more powder gave lower velocities, and I'll guarantee you, the pressure wasn't going down as the extra powder went in. Don't use this as a sole indicator, but take it in conjunction with others and consdier the sum total of them all.