What rate of twist are the Lott owners using on the rifles? Would you recommend a different twist than you are currently using or are you happy with what you have? Thanks.

Craig

[ 12-19-2002, 23:26: Message edited by: CraigP ]

A-Square used a 1:10 twist. They thought that the quicker twist resulted in better penetration.

Very bad: 1:16 as used in Weatherbys,
factory twist nowadays: 1:14, ample stabilisation in air, but a better compromize for penetration is 1:12, for DG hunting at close quarters 1:10 is best for stable bullets travel in game.
Penetration

faster twist means more pressure, aebe.
you'll need to start with bottom loads, or LESS and work up.

jeffe

I would stay with the 1-14 twist on the .458 mag or Lott, I did and have had no problems with bullets or accuracy what so ever. Most barrel makers that I spoke to also recommended that twist.

jeffeosso - It is always great advice to work loads up in a new bore, however, your statement that faster twists increase chamber pressures contradicts published pressure test data. Where did your information come from?

Remember that peak chamber pressures are reached when the bullet is approximately 3 inches down the bore or .0005 seconds from initial powder ignition. The difference in degrees of rotation within 3 inches between a 1:16 VS a 1:10 bore is quite small - about 40.5 degrees over 3 inches. In short, chamber pressures are not effected by changes in �normal� twist rates. In fact, variations in primers have a far greater effect on chamber pressures than twist rates.

[ 12-20-2002, 21:09: Message edited by: Zero Drift ]

Zero,
This is in several reloading manuals, Ackley quoted. and I have found this with my own experiments. This is also in ackley's books. Think about it this way, a smooth bore (at rifling diameter) will have less drag, and thereby less pressure, AEBE.

Maximum pressure does not always take place at ANY Specific POINT in the barrel, as that's fully related to the powder burn rate. I can show you computer models (almost all the relaoding software) that will show you time and barrel distance for max pressure. Let me assure you, it varies with powder, and barrel throating (freebore.. ala weatherby)
In my experiment, I have a 1x16(douglas) 1x14 savage 99, and a 1x10 (douglas) in 358 win.

Yes, I know you could say it's different barrels, but here's the story.

The 1x16 will take more than 2 grains more powder than the 1x10, as the same length OAL, bullet , primer, powder, and same DAY. This is inline with Ackley's findings, which I am more than happy to duplicate, as long as it's safe.

I had the 1x10 custom ordered, as I knew the case had marginal capacity for what I desired , that being shooting long arsed barnes bullets. as for oal, the measured difference is only .002 between the guns, the 1x16 being shorter

Where are you getting published data that this would be different? I would be interested in reading that. As twist increases drag, the resestence to forward movement must increase. This is simple "screw type" physics. Another example, 2 screws, 8x24, and 8x32.. which will require more FORCE to set the same length? 8x32, of course, and that is twist.

don't mean to sound didactic, but this is the published data that I have read, experienced, and retested. If you like, I'll be glad to share my shop, guns, and tools with you, and you can repeat for yourself?

jeffe

[ 12-20-2002, 21:46: Message edited by: jeffeosso ]

Guys,

I recommend you pay attention to what Norbert has posted about twist, and follow his link to his test results on penetration. He does almost all of his shooting with a .458 Lott as well (at least what I see on his website).

Typical discussions on twist relate to how much is enough to stabilize the bullet in air. This is usually known as the lowest effective twist school for the bore size. What Norbert's tests show is the stability of the bullet in the end game: the animal -- where it really matters.

The short of it is to over-stabilize in air to have enough stabilization on the bullet so it continues to penetrate in a straight line path in the animal.

jim dodd

I once comtemplated going the "1 in 10" twist rate when thinking of the .458 LOTT, but decided against it after listening to several people who where in the business of making barrels and big game rifles. I stayed with the "1 in 14" twist and I don't have any problems stabilizing bullets that weigh 500 grains. My penetration in the LOTT chambering is ample for what it was intended for, backing up my other rifle in a .475 caliber. The thought of spiking up the pressure wasn't something I wished to gamble about at the time. Aside from that, I got to keep the orginal barrel on the rifle and just rechamber it out, saving a couple of bucks in change.