Different designs.
 

Why/how does bullet design/make, effect the max powder charge for any given bullet weight?
Example: Hodgdons lists max load for 243 x 65 gr vmax at 42.7 of IMI4895.
Their max load for a 62gr Barnes is 40.5 using the same powder.
Until reading this I assumed the lighter bullet could safely use more powder than the heavier one!
Ken.

Lighter bullets requiring lighter charges
 

I have noticed this before too, especially with some Sierra pistol bullets. I am not familiar with the bullets you mentioned but I would guess that the lighter bullet has more bearing surface area. I think that in some more extreme cases the speed and use for which the bullet was designed (heavy jacket for deep penetration vs. target or varmint type bullet) might cause this.

Just some speculation on my part - and I haven't had any coffee yet so that is my excuse if this makes no sense to anyone else. :)

With my nearly non existent knowledge of such
 

forms of physics, I'd have to say ^^^^^^^^^ what he said about bearing surface.

As far as pistol pills, I believe that jacketed requires more powder than lead.

Ken,
Your answer may be in the bullet itself. Was the Barnes bullet of their solid design or was it a Verminator or some other lead cored bullet? A solid copper bullet is harder so it creates more pressure than a lead core bullet. It's been a while but I think that's covered in the Barnes Manual, which is about the most useless loading manual ever created IMHO. If I did in fact read that from the manual I have, you can rest assured that's about the only nugget of useful info in the whole book.

Furhunter,
Hodgdons say Bar VG FB. Means nothing to me as I've only ever used Berger, Sierra and Hornady bullets.
Thanks for replies.
Ken.

Varmint Grenade Flat Base

Bearing surface is the culprit.

different designs
 

Just remember the more bearing surface, even if weight is the same, will mean more friction, which in turn will cause more pressure.:eek: Believe it is a law of physics thing.. :) Bill K

Bearing surface, core composition and jacket thickness and composition all contribute to the pressure generation as well as it's speed of progression.

Given all the answers agree, I suppose it will be okay to stoke the 62 grain Berger up a bit more than the 65 gr Berger max load.
Thanks to all,Ken.

The other thing with berger data with VLD's at least is they limit the speed to what the bullet performs best with. An example is the big 7mm's. I asked for data for the 7 dakota, STW, and RUM. Even though the rum has much more capacity that the others the load data kept the speeds exactly the same. VLD's work best right around 3000fps. Their data didn't go over......

Aaron