There is utterly no need to exceed 2250 fps with a .458 of whatever persuasion.

But carry on. I enjoy the discussion. This is an interesting thread, just for perspective and the whole blah, blah, blah, bluster...

Yep 2250 fps with 500-grainers in the .458 Lott is the usual maximum without any blah-blah.

You guys are doing the twist again.

Remember that artillery tests showed about 1/2 of one percent increase in pressure with the same loads in a 1:7.5" twist versus a 1:15" twist.

If I had any hope of getting .458-cal/500-grain monometal softs or solids to perform properly in a 450 Ackley or .458 Lott, I would use at slowest a 12" twist. 10" twist would be better yet.

Really now, if the 450 Ackley is about 4% larger in case capacity than the .458 Lott, then the Ackley should do about 23 fps faster than the Lott.

Any tricks of throating and long loading that can be done to the Ackley can be done to the Lott.

Any velocity gain of an 18" twist versus a 10" twist in a Lott or ackley should amount to about 12 fps for same pressure.

There are many factors involved in the rifle and the ammo that have hugely greater effects on velocity and pressure than twist rate does!!!!

Think of TWIST as more like Chubby Checker than The Boogey Man.

All of the above quantitative data was found written on tablets of stone.

Why 2400fps- M(V )squared- Max penetration and max EFFECT on game. The difference really has to be seen to be believed. I was sceptical at first,I became a believer. It's the sweet spot between too little penetration and over expansion with most modern bullets.
Sorry Ron a Lott just isn't a Ackley. As for Artillery tests what relevance does that exactly have to a bonded jacketed bullet in a small caliber barrel. Have you personally studied the pressure differential? Where is your data? Can you show it to us please. My empirical data says it increases pressures significantly such that you have to load down significantly and will never achieve the velocities possible with a slower twist. Do you actually own a.450 Ackley? Have you actually shot one at anything? I'd like a honest answer cause I do own both and have shot Buff with both! A 1:10 twist is pretty much worthless unless you shoot lead pencils and you know it( a 500 gr woodleigh doesn't work well at all with a 1:10 twist). TRY a good 1:15 you'll like it and you too will actually be able to match the published velocities I routinely accomplish. I can fix your problem, I have a pipe wrench!-Rob

Moose, marmots, water buffalo and various inanimate targets with various:

460 Wby x 2
450 Dakota x 1
.458/.338 Lapua x2
450 NE x 1
450 Barnes Supreme x 1
.458 Lott x 2
.458 WinMag x 3
.45-70 x 1
.45 LC x 1

I still own them all except the two 460 Wby's and one .458/.338 Lapua, which were rebarreled or traded off.

Regarding your "lead pencil" bullets: do you consider them to be wooden saboted graphite darts, or what?

With my considerable experience in .458 Caliber rifles, I would never consider building one with slower than 12" twist, even the 450 Ackley imitator of the 450 Barnes Supreme.

I am not interested in getting 2400 fps with a 500 grainer from a 450 ackley. Too tricky and too much blah-blah. No real difference in 2250 and 2400 fps on game.

Why would I want 15" twist when 14" twist is common in factory rifles? If I wanted something special it would be a faster twist for monometal copper "pencils."

I consider the .458/.338 Lapua Magnum the most interesting, and mine has a 23" McGowen stainless 1:12" twist.

Think Chubby Checker, not Boogey Man.