Which load?

[garandman]

I'm trying to decide btwn 2 loads in my 224 Valkyrie:

Load # 1 -

• Bullet: 85.5 Hybrid Target
• Powder - 24.3 gr AR-Comp
• Velocity - 2880 fps
• BC - 0.524 (G1)
• Standard deviation - 7.0 fps
• 100 grp - 0.50"
• 400 yd group - 2" (far as I've shot gun yet)

Load # 2 -

• Bullet: 80.5 Berger Fullbore Target
• Powder - 24.7 gr AR-Comp
• Velocity - 2980
• BC - 0.441 (G1)
• Standard deviation - 4.0 fps
• 100 yd grp - 0.50"
• 400 yd grp - 2"

Interestingly, both have the same point of impact at 400 yds.

So I guess my question is... as I work out to 1,000 yds, is the slower bullet with the higher BC the way to go (85.5 Berger) of the lighter bulelt with the lower BC (80.5 Berger) ?

To my understaanding, either bullet will have a predictable trajectory over changes in velocity, until hitting transonic speeds. So, IF I'm getting near transonic speeds at 1,000 yards, I'd want the higher velocity, lighter weight bullet. Not sure if 5 grains will make much difference in bullet drop, tho, theoretically, heavier bullets will have more inertial mass, maintaining velocity but will drop more over distance.

But .... a higher BC bullet will be more stable over distance.

I know the REAL answer is "try it and see" but I'm also interested in the theory involved so I might anticipate which bullet will be better from 400 - 1,000 yards and then as I shoot, I can see if actual matches theoretical.

I guess I'm kinda a nerd that way.

Your ideas appreciated.

 

[Forum Boss]

1. I don't care about your standard deviation. What is your EXTREME Spread for 5 shots or 10?

2. Shoot 10-shot groups at 200 yards, over flags.

3. With a ballistics program you can compare wind drift at 1000 yards. However, unless you will actually be competing at that distance I would just pick the bullet that shoots best at 200-300 and which has the best bullet consistency (in base to ogive measurement).

 

[Evan]

I'll take load #1 as the example:

What happens to your point of impact at 400yards as you go from, say 24 up to 24.6gns? What you should see on the target is the point of impact will oscillate as you powder charge changes. For a "positively compensated" (I think is what people call this method) load, you should have a slightly lower POI at 24gns, it will climb slightly to 24.3, and then gradually start to drop again as you go up to 24.6 indicating that you are in the flattest part of the POI. Sometimes I don't see the "drop" on the high side, but I usually always see the rise on the low side of the node and keep going until it flattens out.

I've never been a believer in "waterline" because shooting out on the open prairie, as I do, the wind causes both vertical and horizontal dispersion so aiming for a "flat waterline" on the target is illusory.

I would give the 85.5 the nod if they shoot as or more accurately than the 80.5, but I've not had any luck with the 85.5 in my 22BR for pure accuracy.

 

[garandman]

1. I don't care about your standard deviation. What is your EXTREME Spread for 5 shots or 10?

2. Shoot 10-shot groups at 200 yards, over flags.

3. With a ballistics program you can compare wind drift at 1000 yards. However, unless you will actually be competing at that distance I would just pick the bullet that shoots best at 200-300 and which has the best bullet consistency (in base to ogive measurement).

Thanx.


ES is about 17 - 20 fps. For both.


Maybe ever'body already knows this, but.... why is base to ogive the significant measurement, rather than either (1) base to tip, or (2) bullet bearing surface length on the lands?

(These are both boattail bullets)

 

[Forum Boss]

Base to tip can vary by multiple thousandths even among good bullet brands and will not tell you actual distance to lands or engagement in lands.

Bullet bearing surface length is hard to accurately measure, and again, won't reveal true engagement in lands (or distance to lands).

Best bullets I've loaded held 0.0015" base to ogive for 97 out of 100 bullets in box, and two were about .0025". I've seen not-so-good bullets vary by up to .020" base to ogive (for a few in a box).