Home Forums Reloading Reloading Software 458 QL data

Could someone run this for me?
458 win mag
Winchester brass trimmed to 2.49"
Woodleigh 550gr. RN SN SD 375 BC .340
WLRM primer
73gr H335
C.O.L. 3.31
24" bbl.

I contacted Woodleigh and they responded back saying they have no data using H335 for any of they're bullets.
Basically I just want to know if the above load is below the max pressure.

Without pressure testing there is no way to know. QL provides approximate pressures but there are many factors that weigh into the peak pressure generated in your rifle.

Looking at published data for 500 gr Hornady's using H-335 your charge weight looks like it would be in the ballpark of a max load. What I would suggest is working up loads with the Hornady 500 gr and chronographing them to see how your rifle compares to their published data, and then correlate it to your 550 gr results.

Hornady's data shows a velocity of 2150 fps with a max charge of H-335 with 500's. From work I've done with similar rounds I'd expect that your max load with a 550 gr will produce 1950 fps. If it were me and I was getting 1950 fps with a 73 gr load, I'd consider that my max charge weight. If I was getting higher velocity I'd back off the powder charge. I wouldn't exceed the powder charge as in my experience when you increase bullet weight by 10% the powder charge decreases by 5% which is right at where you are at.

How I come up with 73grs. Is I have data for that bullet using benchmark powder 73grs. And benchmark & H335 have about the same burn rate.
And I have about 8lbs. Of H335 and zero benchmark.
I have no access to a chronograph either.

I would most highly recommend investing in a chronograph when you plan to work up a max load with a powder that doesn't have published data.

Burn rates are not absolute and while two powders may seem to have the same burn rate in one cartridge, they may significantly deviate in another cartridge. About the same burn rate could mean a max load is 69 gr, or 73 gr.

Yea no chronograph in my near future. So I was just hoping someone could run the numbers through QL for me and at least get a ballpark figure on presure

Quickload is notoriously inaccurate with big straight-wall cases, seriously overestimating pressure.

I have pretty much given up on it for my .45-70 because every prediction with every powder is so far off until I shoot a baseline.

You have to increase case capacity by several percent, and it's different for each bullet weight.

Hodgdon's data has been very close for me, but they probably are not using the components you are asking about....

I like Hodgdon data too but yes no data for the 550 Woodleigh.
I got data for Woodleigh 458bullets from a member on this forum. But no H335 loads.

I've had people run QL for the 458 Lott with the same result that the pressure estimates are way off. With the 458 there are a lot of variables with varying throat lengths depending on the manufacturer, bearing length and hardness of the bullet which can change the peak charge a several grains from load to load for the same bullet weight. And some powders will start to act weird and show pressure spikes when you get out of their sweet spot.

The two ways to see if your gun runs higher pressure is a strain gauge or a chrono. If you're not going to get a chrono it would probably be better to use 70gr as a top charge to be on the safe side. Working up loads with unpublished components without a chrono can be risky. I've done so and things often go well, but I've also had some unexpected pressure excursions.

Quickload's default settings do show that Benchmark is slightly faster burning than H335, so at a given charge weight the pressure *should* be lower using H335.

But, I defer to 458 Lott's statements concerning burn rate/cartridge and second his recommendation on a chronograph, or at least the use of one.

While Quickload is amazingly accurate in predicting bottleneck case results when given good measurements, I do not trust the results with big straightwall cases. It's propensity to overestimate pressure makes it necessary to chronograph a load, then adjust the case capacity until the results resemble actual data.

If I could only have one piece of equipment to choose from between QL and a chrono, it would be a chronograph.

Does your data for Benchmark include what pressure it is operating at?

No I didn't receive any presure data using benchmark. But it shows a velocity of 2110fps with 73grs. but no bbl. length or gun model.