SAECO 540 GC in .458 WinMag : Going For The Fence

[Idyhojo]

-]-[owdy..! Have a push-feed M-70 African thru which I've been shooting Barnes 350 X bullets at flattened-primer pressures. Recently purchased a two-cav SAECO for 540 GC. Planning on Linotype. Would like to load her right up there, as well. Am wondering if any of you fellers would care to relate your experiences with this caliber, this bullet at those speeds n' pressures, and perhaps even tell me how to best get there... Am waiting for Linotype shipment to arrive, so I don't even know if these things will fit inside. Have a Lyman 450 sizer with a .459" die (used in my .45-100 BPCR Rolling Block) but know that BP lubes ain't gonna cut it with this. So, I'd appreciate hearing about your experiences with lubes. Don't want to lead the bore but accuracy isn't important for close range practice and I will happily take what I can get. Thanks In Advance!

[GBertolet]

I have had some experience with the 458 using cast bullets. I prefer the RCBS 300 gr gas check bullet ( mine weigh 320 gr w/gas check ), using 4759 powder for about 1640 fps. I did buy a Lee 500 gr GC FP mold to play with, in an attempt to duplicate factory ballistics. Using enriched WW, diameters as cast with both molds drop around .460. I lapped out my Lyman .459 sizer to .460, as my groove diameter is a little over .459.

I started having problems with the 500 gr bullet, when approaching factory velocities. With fast burning powders, ( Rx7, 3031, etc ), accuracy was terrible, and I actually has some bullets tumbling. When progressing to slower burning powders ( Varget and slower ) , accuracy began to improve at the 2000 fps range.

I think due to the short case design, intended for standard length actions, the pressure is 45 to 50K, for full power loads. This was too much for my alloy of tin enriched WW. I think the slower burning powders are more gentile on the bullets, although I experienced no leading whatsoever with any load using the enriched WW bullets. I was using 50/50 alox- beeswax. Next step will be to heat treat the bullets, and repeat my tests.

I think you are wise to start with linotype for your initial tests. Your chances of getting good results will be improved. Although the 500 gr bullet is not the same as your 540 gr, I think the principles are the same.

I am sure you are aware that the recoil of these loads will get your attention. There is a HUGE difference in recoil between both the 350 and 540 gr bullets at full power loadings.

[bobthenailer]

I used the Saeco #020 540 gr gc boolet in my Browning BPCR in 45/70 with excellent results !
i used 50 grs of 4831 and a Fed lr match primer for 1,350 fps and a 2.5 " 25 shot group @ 200 yards using a scope.
I still have the Saeco # 017 350 gr fpgc that i have used in the Browning as well as several friends 45/70 using 5744 powder , i also gave another friend some for his 458 mag and he asked me for more and said they shot well , but i dont know the load.

The 350 gr would not stablize in my Brownings barrels twist as it was made for heavy bullets , also the 540 gr bullet may not be fully stabelized at 100 yards ,might have to shoot at 200 yards as was the case with my Browning rifle.

IMO i would be looking for a lighter bullet the 350 gr is a excellent choice ! those 540 gr bullets do have more recoil evan at 1,350 fps

[Idyhojo]

Okay, gents, and many thanks to both of you..!

[Nobade]

I'd be leaning more toward air cooled wheelweights or something of a similar hardness and paper patching those boolits to whatever diameter is a snug slip fit in a fired case. I suspect you're going to have some considerable frustration trying linotype and full pressure loads, especially if you intend to use them on game.

-Nobade

[offshore44]

I've got some experience with the 458 Win Mag and cast. Here's what I've discovered so far.

First, the rifle: It's a CZ American Safari. The barrel is 24" long and has a 1:14 twist. The bore is tight and the chamber is generous. The rifle was purchased explicitly for shooting cast, and has shot nothing but cast since the factory.

I have tried a bunch of different powders, and a bunch of different cast bullets. The one thing that I have discovered is lighter bullets can be run faster (much faster) in my rifle with equal accuracy. The 350 grain Saeco's can be run up to about 2,600fps or a little more with fine accuracy. Heavier bullets, in the 400 to 500 grn range seem to shoot best when run about 2,000 to 2,100 fps range. They can be run faster, but the fun factor runs out very quickly as recoil, even with a heavy rifle, starts to tell on accuracy. Rifle powders on the faster end work better than slower rifle powders. Softer lubes give better results than harder lubes.

Lyman #2 alloy is about the top end for bullet hardness, anything harder seems to degrade accuracy. An alloy around 12 bhn has worked best for me so far. Balance the bullet hardness with the powder speed for best results. I use a 94-3-3 alloy at 1,800 fps, paper patched 405 grain bullet for hunting.

A note about the 458 Win Mag throat. It is usually large and long. Bigger and longer than a person would ever suspect. For any sort of accuracy, you need to fill that throat. That could mean a bullet diameter as large as 0.462". Go as large as will reasonably chamber and extract without pulling a bullet. You will reach a point as you work up in diameter where all of a sudden your groups will shrink drastically. Like go from 4-6" to 2 1/2 - 2". Start playing with powders and loads at that point. The major key to the 458 is bullet fit, fit, fit. The round really wants to shoot cast, and will surprise you with accuracy at all ranges with a little work.

A note on paper patching. The 458 responds especially well to paper patching. The key, again, is fit, fit, fit. A full case or filler greatly increases accuracy.

You can load a range of different types of cartridges for the 458. Shot (410 equivalent), round ball plinkers / varmint loads, deer loads, big game loads, and dangerous game loads.

[Idyhojo]

Another big THANKS..! I'm not really sure about my Win M-70's chamber dimensions. What I plan is to try the SAECO #020 Gas Check mould with Linotype, and will most likely use the powders and quantities of them recommended for 500 jacketed slugs. Thanks to all who've taken the time to respond!