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375 RUM and the 260 Accubond...

 
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  #29  
Old 12-04-2013, 03:13 AM
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Re: 375 RUM and the 260 Accubond...

N570 is really slow like Retumbo/R-33. I doubt it will work well in a 375 RUM.
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  #30  
Old 12-04-2013, 03:23 AM
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Re: 375 RUM and the 260 Accubond...

VihtaVuorri N560 vs. IMR4831

Just did a comparison of VihtaVuorri's N560 and some similar common place powders and in 300 WinMag and 338 WinMag n560 and IMR 4831 use very similar charge rates. The N560 seems to be able to use very slightly higher charges in some cases. So my best guess is that if you know a safe load with IMR 4831 then that is a reasonable top load for N560.

Compared data in both Sierra's 5th Edition and Lapua's online data. Sierra is using less for its top loads that Lapua lists as top, apples for apples.
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  #31  
Old 12-04-2013, 07:42 AM
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Re: 375 RUM and the 260 Accubond...

Quote:
Originally Posted by Kennibear View Post
VihtaVuorri N560 vs. IMR4831

Compared data in both Sierra's 5th Edition and Lapua's online data. Sierra is using less for its top loads that Lapua lists as top, apples for apples.

The pressures are measured differently in the Sierra and Lapua manuals. Sierra uses Saami standards and the transducer is at the lower third of the casing (roughly). Lapua uses the case neck for their transducer location. There are other differences so it is still rather an apples and grapefruit comparison excepting the fact that both systems if used correctly will produce safe loads for the cartridge in question.

Not to rain on your parade but pointing out that there ARE differences and it is best to excercise caution using Euro data compared with US data.

Cartridge Pressure Standards
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  #32  
Old 12-04-2013, 04:20 PM
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Re: 375 RUM and the 260 Accubond...

Lefty7mmstw

Very familiar with the difference between SAAMI and CIP. Also pay attention to the difference between the various manuals. Let me state right here I believe you should buy every manual you can find. Case in point:
Hodgdon's and Hornady have a long relationship developing ammunition together. Hodgdon's Superformance and LeveRevolution powders were developed for Hornady. For the 375 Ruger the top loads of Hodgdon's powders differ between the two. Hornady is the only source of cases so that is not a variable. Which do you accept? I assume that neither is gospel in my rifle. I test every load.

I compared common loads with the same bullets (Sierra's) in both manuals and noticed that Lapua loads heavier charges, the real difference in components being cases and primers. Some of Sierra's loads use Fed #215 LRM and that change alone would require a reduction in powder weight as the Fed is one hot spark plug.

CIP measures at the case mouth so there is no factor applied for the cartridge case. SAAMI makes some (bold) assumptions about the pressure restraint of the brass case as the transducer is over the case and it absorbs some of the pressure. SAAMI adds a (large) assumed pressure factor to the raw data to arrive at the reported pressure #. I, like many others, think CIP is the more accurate of the two. And yes, their chamber/bore specs are different.

In my youngest son's 300WinMag, matching the Sierrra components, two loads, 150gr SpBT/ 75gr 4350 and 200gr SpBT/75gr 7828, both indicated (and later tested on a Pressure Trace II retrofitted to the absolute max pressure. I have used Max loads from Sierra for 30/06, 45/70, and 556 that were mild, the 556 in a match chamber (NATO 556 throat). What's up with that? S.O.P. in my experience.

The upshot of this is an assumption I wrongly made thinking everyone thinks like me. I research all my loads from as many sources as I can find. The lowest listed maximum load is my assumed maximum until proved different IN MY RIFLE! The heaviest load I find searching out Load Data is my assumed "never exceed even if it tests safe" maximum.

This has worked for me for 40+ years of reloading. I still have all my fingers and both eyes. I raised three boys and, after their teenage years, my hair, hearing and sanity..... not so much....
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  #33  
Old 12-04-2013, 06:10 PM
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Re: 375 RUM and the 260 Accubond...

Kennibear,
you are spot on with your post and it looks like you are prudent in your research.

I was simply pointing out that the data sourcing used different pressure measurement and to be rather careful with correlation. I too rummage through the various manuals in search of patterns and to weed out the oddball loadings, and to also find a manual that my rifle rather closely tracks.
Have a good one,
lefty
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