I,m sending a 458 Lott reamer back to get modified. Since it will be a custom reamer ,what freebore diameter should I specify? The one I have now has .459" diameter. I didnt want it too tight that it might cause problems with slightly dameged ammo and a buffalo charging me. Then I didnt want it so loose that the bullet rattles and cartwheels its way down the freebore. What freebore diameter is best for .458" dangerous game chambers

My Lott reamer throat diameter, ahead of the neck, is 0.4583". You can go to 0.4585" or 0.459" or so and still be OK for a hunting chamber. (Some chambers are bigger). One thousandth is not very much!!! For a hunting chamber, especially a DGR, I would err on the large side, say .459" or so. Throat length on my reamer is 0.406". (This long throat accepts any and all bullets, mono metal solids, etc., and keeps the pressures down.) (Careful readers will note that this reamer is essentially a long throated 450 Watts)

I have shot 5/8" groups, three shots, 100 yards, aperture rear sight, with a 458 Lott chambered with this reamer. 22 inch No. 6 barrel, M70 action. 500 grain Hornady soft at 2300 ft/sec.

Note on Lott case length: Jack's standard chamber is for brass with a length of 2.800". My reamer cuts a chamber for 2.85" case length (length of the case section of the chamber on my reamer is 2.865"). Why? Because there are some Lott cases (Old A-Square and some PMC) in the world with a case length of 2.85", and I have several cases with a length of 2.860". So, if your rifles will be used in Africa, and the use of local available cartridges may be in order, then you should be cutting chambers for the long brass. Otherwise, if your ammo is lost in transit to Africa, those Lott cartridges you found under the Outfitter's safari vehicle seat may not chamber.

There have been good discussions on the 458 Lott and chamber length in the past here on AR, search the big bore forum.

You should pay attention to the neck diameter of a loaded case, crimped. Some chambers have a neck diameter that will just barely accept a non crimped case, crimp the case, leaving a slight bulge, and those cartridges may not chamber. Make up dummy rounds, crimp, measure the necks, and adjust the reamer neck diameter accordingly. 0.003" to 0.005" over case diameter is about right for a DGR chamber that needs to accept any and all cartridges in the heat of a charge. Again, I would err on the large side. Don't worry about working the brass when firing and resizing, we ain't talking about benchrest rifles here, and in most instances you will never find the brass after shooting that Buff.

A nice tool for reloading is to make a case gauge from a short section of 458 barrel. Chamber this section so a loaded round will have the base flush with the chamber end when a loaded round is inserted. This way, it is real easy to verify that those loaded rounds will chamber in the rifle. Just be sure to engrave the rifle serial number and caliber on this gauge and keep it with the rifle.

PS, the best gent for reamer grinding is Dave Kiff, Pacific Tool, White City, Oregon USA.

Thanks a lot for this info John. I will make sure that he doesnt give me the "match version this time" By the way it was Dave Kiff from Pacific Pricision who ground the reamer the first time. I,m about to send it back to him to get modified.