Since wildcat chambers can very quite a bit, I'll start with a caveat about carefully working up to max loads. The rifle I had definately had a long throat, which may explain why my max 500 gr load was shown as producing high pressure on quickload.

The gun was built on a P-14 enfield, with unknown barrel brand, and unknown twist, barrel 21 1/2" backbored 1 1/2" w/ 10 1/4" holes. I assume an effecive length of 20" for velocity comparisons, and if you shoot a 24" tube, expect an extra 100 fps, possibly, but not much more.

Standard on all loads: Remington 416 brass, fireformed and trimmed to 2.800", with CCI mag rifle primers sparking them off.

First thing I did when I got the lott was get a box of 500 gr hornady softs, and work up a max load. My approach was to compare 458 win mag data to 458 lott data to get a feel for how much typical charges varied between the cases. From that, it looked like the lott had a 8-10% larger charge, by weight over the win mag. Based on that, I looked at a few different loads for the win mag using RL 15, and used the max win mag load as a starting point, and worked up in 2 gr increments. I found in my gun, max accuracy was with a charge between 85 and 87 gr. I was getting 2270-2280 fps with the 87 gr charge, and decent groups. I did try 88 gr, but the velocity spread increased, as well as groups, so, for my gun, 87 gr was a max. All cases extracted effortlessly and had no signs of pressure

After going through a box of 500 gr bullets, and 1/2 way through a second box, I thought I'd give the 350's a go. I used the same approach as with the 500 loads with RL7. I didn't want a max load, but a minium accurate load. With the 350 gr speer, 76 gr produced tight groups and 2400 fps. With the 350 gr rn hornady, I had to go up to 80 gr for accuracy, and they averaged 2525 fps. These are not max loads, and achieved my goal of matching 458 win mag balistics.

I did try a few of the 450 gr X bullets I was given, but didn't get a chance to develop a load. I will say RL15 is too slow to stuff enough in to be useful, as I had expected. I also found my starting load with RL7 to be too hot, and it produced the only cases I lost, with loose primer pockets. I expected RL7 to be too fast, and at reasonable pressures, the velocity would be less then ideal based on how my hot loads clocked. The 450 X is a long bullet, compared to the 500 hornady, the X seated to the canalure makes the lott into a win mag capacity wise. Perhaps a longer barreled lott and more apropriate powders would produce useful velocities with the 450 X, but I'd stick with the 400's in a short barreled lott.

Paul:

You might be intersted in these results.

458 Lott
CZ 550 , Clymer Reamer
IMR4320, C= Compressed, VC= very compressed CCI 250 Primers BeLL cases Crimped
Gr. IMR 4320 Hornady 500 gr. FMJ Speer 500 gr. AGS Solid
fps fps
80 2146 C 2088
83 2236 VC 2174
86 2326 VC 2238
88 2392 VC 2296 C
90 2355 C

No signs of high pressure