Im getting a 458 Lott reamer modified.(made to suit the newer 2.850 cases). While it is in being modified ,If the freebore diameter is wrong then I can change it as well. For a .458 cal ,what is the best freebore diameter. At the moment mine is .459" diameter .250" length and 1.30 angle

Sir cr500,

My gestalt: Most of the .458 caliber chamber reamers of successful cartridges have throat specifications like so ,,,



freebore diameter 0.459" to 0.460"

freebore length of 0.200" to 0.300"

leade angle 1.5 degrees to 2.5 degrees



A notable exception is the .460 Weatherby:

0.4585" free bore diam.

0.7500" freebore length

1 degree 5' 20" leade angle



And the odd duck .458 Winchester throat:

The throat is entirely leade of angle 0 degree 29' 30" that starts off as a huge diameter of 0.4690" and tapers down to .450" bore/.458" groove over about 1.130".



I think you have good specs. Fine choice. The only change I would allow is a max freebore length of 0.300", no more, but keep the same diameter (0.459") and leade angle (1.5 degree or 1 degree 30').

Thanks for the info RIP. I will stick with the 459" throat diameter and 1.30" leade angle.

Ron,

John Barsness reported in the latest Rifle magazine some commentary on scopes and recoil. It seems D'Arcy Echols sent Leupold a .458 Lott rifle to test in their "recoil machine". Leupold discovered that the recoil velocity of the Lott is the highest they have measured, including the .460 Weatherby.

I was wondering if the famous Weatherby freebore is the mechanism holds down the recoil velocity?

D'Arcy says the Lott is a killer of variable scopes.

There is some discussion of the Rifle article in the Optics Forum too.

jim

Jim,
The Clymer reamer for the 2.85" cased .458 Lott has a throat that is

0.4585" freebore diameter
0.4600" freebore length
2 degree leade angle

That is odd as far as recoil effects, and I don't understand it.

I also can't say what effect the exiting muzzle pressure might have on recoil, if anything beyond the usual parameters of rifle, bullet, and powder charge weights and velocity.

I think the recoil calculator formulas are good approximations in most cases, but not all.

The analysis is beyond me.

I think in both theory and practice that a calibre loaded to lower pressures is easier on a scope than the same ballistics from a full pressure load from a smaller case.

If you loaded a 460 to 2300 and with slower powders then I think the velocity a couple of inches up the barrel would be less than a 458 Lott loaded to 2300. Thus the rifle would have a lower rate of acceleration.

The very long freebore of a 460 may also contribute to this

If we could have a setup whereby a bullet with a muzzle velocity of 2400 f/s achieved that by increasing its velocity by 100 f/s for each inch of barrel travel then such a calibre would prove to be very easy on a scope. There would be no difference to the shooter as the rifle would reach the same velocity.

Mike

As for the recoil of a 460 weatherby being lower than a 458 Lott, maybe the Lott was a very light one and the 460 a heavy one or the 458 Lott had very heavy loads or something. I have no real problem with a 458 or 458 Lott (I still dont shoot them as well as I would a 222) but as for the 460 weatherby I tried, it realy knocked me around. The 460 I tried was fairly light and had no scope(which is good because it would have clobbered me),had 500 gn factory ammo and when I fired it ,the second shot would have been way too slow( for me anyhow).
Then as for the freebore, lowering recoil, you may have a point ,it could be the same concept as shotgun barrels being backbored to reduce recoil.

CR500, see my reply in the Gunsmithing room. Some important stuff in the post.

Re recoil, 460 Wea vs 458 Lott: Lotts (pun intended) of variables: Throat diameter, freebore length, leade angle, rifle weight, barrel contour and weight (where that weight is located is important, I like no. 6 barrels on the 458's), stock design, cast off, drop at heel and comb, pitch of the butt, how high the sight line is above the bore ( along with drops and cast off, determines if you are stretching your neck to see the sights or pushing your cheek hard into the comb), pad width and height, weight of rifle, load and velocity of bullet, and a whole bunch of other things all add up to the felt recoil. A note, just about all factory 460 Weatherby rifles are equipped with a brake!!!! so go figure.

A stoked up 458 Lott, in a 8 pound rifle, has a fierce recoil. A 9-1/2 pound Lott, properly stocked, shooting 500's around 2250 to 2300, is not bad.

Most of the Lotts I have seen, especially 458 Win conversions, have a poor stock design for iron sights and really work on the shooter.