458 Win Mag Reloading

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jsquig

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Just loaded up 20 rounds of .458 Win Mag with Hornady Brass, 350 Gr Hornady round nose interlocks, CCI Magnum Primers and 77 Gr. of H 4895. Hodgdon lists this as a starting load, but it is almost, or slightly compressed to get it to the cannelure for crimping. Would there be any harm in dropping the load down more? This is listed as a 2400 fps load, so it shouldnt be any issue with it not making it out of the barrel, and even cutting it back to 60 grains you'd still have 75% case fill.

Basically what I'm asking is what is the basis for "starting loads" are they minimums, or just a recommended load to start working up to max (which in this case is 3 grains more)?
 
Are you worried about compressing the powder or do you want to reduce your velocity some? You will find most, if not all, loads in the 458 WM are compressed loads, this is perfectly normal in the 458. I personally like compressed loads and try to work with powders that will give compressed loads, in every high intensity cartridge I load for. I found years ago the compressed loads are USUALLY more consistent, with a relatively low ES. Some loads I have worked with are extremely compressed and I have not had any pressure spikes or any other anomalies, however I did find some of the slower RL series of powders (RL 17 and RL 19 for sure) don't tend to like compression for some reason and do tend to become a little erratic, but these are the only powders I have experienced this with.
IMR and Hogdon powders seem to love to be compressed, some of my most accurate and consistent loads are heavily compressed IMR and Hogdon loads. My only warning it make sure you get it right the first time because they are a real PITA to have to pull bullets and then scratch and scrape the powder out of the case............
 
I was thinking more along the lines of reducing velocity. No problems with compressing loads, if you're running a 458 its par for the course as you said. I guess its more of a question of what to starting loads represent. Are they a minimum (which I can't see this being the case), or are they just kind of a moderate point to start working towards max from? I'm not sure why, but I've always look at it as a minimum in the books... but I've never really put much thought in to it before ...
 
The reducing below mins has no adverse effects with some powders but can have with others, one needs to be careful trying loads below posted mins with Win 296/ H-110 and it is not recommended with powders with a burn rate of 4350 or slower. They require X amount of pressure to burn and function correctly, reduced loads just go really erratic with huge ES and lots of unburnt powder.
 
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