Which Bullets are Faster or Slower than Expected?

[Fess]

Every now and then I see a comment about a particular bullet consistently running a little faster or slower than others of similar weight. Unfortunately my memory is not great and I forgot which ones were mentioned. I suspect that much of the effect has to do with jacket construction or how easily and accurately the bullet conforms to the rifling, but hopefully this list will suggest a pattern.

Anybody been surprised with the speed of a particular bullet?

[grayfox]

Guess I never figured the bullet to be faster or slower...
Rather the powder lot# I have, might be fast/slow compared to load data (their powder lot#)
Or the barrel conceivably could be faster/slower due to internal construction, smoothness, imperfections or etc. (Part of my theory on barrel performance has to do with internal friction-losses or imperfection-losses: a varying amount of these could cause MV performance to be less/greater than the published data's setup).

Is this where you're going?

[Fess]

Not really. Every now and then people note that X 120 grain bullet typically runs faster than Y. The bullet itself needs to be deformed and extruded to conform to the lands and grooves of the barrel. A .264 diameter bullet has a larger cross sectional area than a barrel with a .264" dia groove dia and about 35% .256"dia lands. The Grendel SAAMI print calls for a barrel cross section of 0.0536 sqin, and a .264 bullet is 0.0547 sqin across.
I had begun to wonder if bonded bullets, for example, tend to be a little faster than others, possibly since the core needs to be almost pure lead and soft to get bonding. It should take less energy to deform the bullet to conform to the grooves and lands.

[StoneHendge]

The 108 Scenars run slow and the 100s very slow due to the large amount of bearing surface for their weight.

[LRRPF52]

108gr Scenars have the same jacket as the 123gr Scenar, with less core mass. They don’t tend to run as fast as 107gr SMKs, for example.

Some monoliths tend to run slower since they resist being driven into the lands more than cup and core bullets.

The shorter/lighter you go with monoliths, the closer they get to cup and core speeds. 120gr monoliths are a lot longer than cup and core 120gr.