TEMP sensitivity? MRP/4831

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david doyle

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After a decade long love affair with some ammomart surplus powder I need to move on:(

I am looking to get max velocity out of a couple 98 6.5x55s with a 160 grain bullets(>/= 2600fps) I an looking at Normas MRP and H4831 but read a few references in my research to temp sensitivity and now my choice is stalled. Basically we shoot in plus 30 degree down to -30 degrees celcius. I am not worried about 50 fps across that range but somewhere the figure 200fps came up and that is not very desirable.

Does anyone know of a refrence for temperature sensitivity of these two powders/have suggestions for options? I am also wondering where westerners source thier NORMA powders.

Thanks
 
Varget and W760 will do just about the same thing. I've had very little trouble with H4831 right down to -40C. If you're shooting beyond 400m, you might find a bit of difference that would be enough to worry about. It seems to keep my 6.5 bullets within one minute of coyote to that distance. I use magnum primers with H4831. It's not reccomended and I won't reccomend it to you. That may be the reason I don't notice much difference with temp changes.
 
From a bit of research I found that MRP burns about the same as RL-22 but is relatively Stable....That would be my pick for 140's . Cant speak about the 160's as I only shoot up to 140 in the swede.
 
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David, I think you know I am what is often called, "from the old school," so I often have different opinions than many others on here.
While rifles were still pre 64, I had occassion to test many new rifles and sight them in for customers. My procedure was to get a good rest, then fire five cartridges, Norma factory, at a 100 yards, in standard slow fire, but the barrel would get hot. I found that most new rifles out of the box would walk the bullets as the barrel warmed. I have said it before, but the only make I tested that never walked the bullets, was the Schultz and Larsen rifles, in both 7x61 and 308 Norma magnum. Five shots would go into 1¼ inches, regularily. Remember, I was using sporting rifles and low power scopes.
I bought a 270 Sako L61 for myself. I litteraly prayed that it would be OK. But no luck, it walked the bullets. It took three sessions of bedding and tweaking, but it then became one of the most accurate rifles I have ever had.
Thus, every rifle I own has been carefully bedded and I never have to use that expression, "What my rifle likes." They like all good ammo, factory or carefully made home built.
I tested the 270 with different powders and bullets, to get the drop at 500 yards. I would first sight 2½ inches high at 100, then put up an aiming mark on a big enough target to catch the bullets at 500. Here are some figure from my original notes.

A CIL, 130 grain bullet, 60.5 grains of war surplus H4831--34" L at 500.
---------------------- 60.5 grains of Norma 205--32" Low at 500.

A Norma 150 grain bullet, 59 grains of H4831, -- 34 inches low at 500.

150 grain Hornady, 59 grains of Norma 205, 2½ to 3" High at 100, a 6½ inch group, 30 inches low at 500.

130 grain Hornady bullet, 61 of Norma 205, 2½ to 3 high at 100, on at 300 and a 6 inch group 27 inches low at 500.

I never used a magnum primer and at this stage in life we never heard of temperature sensitivety, or otherwise, of powders.
Later, the Noma MRP replaced N 205, because they said it was more stable.

WARNING- Do not attempt to duplicate these loads in your rifle, unless you carefully work up your loads.
I am just reporting what they did in my rifle, which does not mean your rifle.
 
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