Hornady 105 Amax vs HPBT

[js2013]

FYI - in case anyone is interested I tried both the 105 Amax and HPBT today. To my surprise velocities were the same per powder charge and point of impact was very close. I expected the HPBT with its longer bearing service to be faster. The HPBT needed to be seated in quite a bit further to be .010 from the lands like the Amax. Both bullets were moly coated. Nodes were close also and over lapped.

 

[Terry]

Cool, tell us more. Pics?

 

[Nomad47]

According to QL, seating deeper reduces effective case capacity thereby increasing velocity for a given charge.
So that might explain why velocities were similar.

 

[Catfish]

It also raises pressure.

 

[js2013]

According to QL, seating deeper reduces effective case capacity thereby increasing velocity for a given charge.
So that might explain why velocities were similar.

I forgot when I chrono'd the Amax load a few weeks ago the bullets were seated deeper into the case, plus it was 15 degrees F warmer. So the Amax load was seated deeper but had more freebore.

Does QL give any insight to pressure differences between bullets seated deeper in the case vs bullets seated into the lands? I'm wondering which would have more pressure, a bullet seated .040 from lands (so seated .040 deeper into case) or a bullet seated .000 from lands (so seated .040 out of the case)?

 

[Evlshnngns]

What twist is your barrel?

 

[js2013]

What twist is your barrel?

it's an 8

 

[Nomad47]

I forgot when I chrono'd the Amax load a few weeks ago the bullets were seated deeper into the case, plus it was 15 degrees F warmer. So the Amax load was seated deeper but had more freebore.

Does QL give any insight to pressure differences between bullets seated deeper in the case vs bullets seated into the lands? I'm wondering which would have more pressure, a bullet seated .040 from lands (so seated .040 deeper into case) or a bullet seated .000 from lands (so seated .040 out of the case)?

Yes, QL says to add 7000 psi to shot start pressure for bullets seated into the lands. But I think they mean a real jam not just kissing the lands.

 

[Nomad47]

It also raises pressure.

Of course, that's how you get more velocity - all other parameters being equal.

 

[js2013]

Yes, QL says to add 7000 psi to shot start pressure for bullets seated into the lands. But I think they mean a real jam not just kissing the lands.

That makes sense. Regarding jamming the bullet into the lands, does QL make any psi distinction between a moly vs bare bullet or does it treat them the same? Also does it make a psi distinction based on how far the bullet is seated into the case, all other things being equal. Just ignore me if I'm asking too many questions

 

[Nomad47]

There is a box you can check for bullet coating. Then you can also adjust the percentage of "slippery-ness".

I have never seated more than .005 into the lands and when I have, I found adding about 2500 to the shot start pressure worked for me.