Different Max Pressure Spec?

[ElDub1950]

Looking at load data on the Hodgdon site for .40 180gr Berb FP.

The Max Pressure using Winchester Autocomp is 33,000 PSI & Vel is 1060
The Max Pressure using Hodgdon Titegroup is 31,900 PSI & Vel is 988

For the same bullet, why isn't the Max the same regardless of the powder?

Especially since the load data is from the same source.

I've only been doing 9mm and want to do .40 next and want to load for a Vel of 1010, just to match my preferred SD/HD, (Fed HST 180gr)

I don't understand why Titegroup would have a lower Max Pressure & Vel.

[Ferrum]

The pressure in the books are for the specific powder tested. Each powder has a different burn rate and Ba factor, thus different pressure.

Really has nothing to do with the projectile in this case (not going into seating depth)...

[the86d]

Maybe they tested the slower max on Glocks?

[ElDub1950]

I only mentioned the projectile so you knew I was doing an apples to apples compare.

I understand how the burn rate and BA factor cause different pressures for different powder and therefore different load weights.

Perhaps my misconception is that I though Max Pressure was the maximum to prevent deforming/damaging the projectile .. lead can handle less pressure than plated which handles less that FMJ.

Is that not the purpose of the Max Pressure limits.

Thanks for any knowledge you can pass my way.

[BigBronco]

Accuracy. Some company's limit the data when it is pointless to include it for accuracy reasons. So lets say that pushing the Tightgroup to max pressure and velocity opened up the test group size.

I know the Lyman manual does not list powders for a caliber that they felt were not worthy of the cartridge for performance reasons. Yet the Lee manual will any powder that gets the bullet down the Barrel while still safe to use.

[ElDub1950]

Accuracy. Some company's limit the data when it is pointless to include it for accuracy reasons. So lets say that pushing the Tightgroup to max pressure and velocity opened up the test group size.

I know the Lyman manual does not list powders for a caliber that they felt were not worthy of the cartridge for performance reasons. Yet the Lee manual will any powder that gets the bullet down the Barrel while still safe to use.

Interesting, Thanks!

Can I assume that probably the publish Start Loads is also related to where accuracy drops off (in their test gun) ?

[bigedp51]

http://www.handgunsmag.com/2010/09/24/ammunition_40lite_091806/