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Burn rates
ChetStafford
Member Posts: 2,794
How would you figure out a load if a manual doesn't give a load for a particular powder? I use RL-22 in my 300 but bought some Norma Mrp to try and see witch on my rifle likes better I know they are very close in burn rate I will be using Barnes 180gr xlc's Weatherby cases and federal 215 primers
Comments
I guess you're asking about the .300 Weatherby case and cartridge? You state "...my 300..." and "...Weatherby cases..." but don't use the two as one term. You also don't say whether this is a Weatherby chamber or some other custom or proprietary chamber. These things make a difference.
I use a chronograph and extrapolated data from a ton of notes that I have.
Trying to interpolate existing data in a situation like yours is a little tough. Trying to find exact data for specific components can be nearly impossible given the numbers of components available these days. The powder and bullet manufacturers have pulled back some from testing every combination due I'm sure in no small part to the mounting costs of producing and printing the data.
I work with wildcat cartridges most of the time so I routinely have to solve this type of problem. Generally, you can try to locate data for a cartridge that is similar in capacity and adjust the starting loads down a touch in order to add a little buffer room to the first test shots. Your biggest constraint is the bullets. The monometallic construction of the Barnes bullets present a unique set of problems for reloaders to overcome.
Barnes bullets are long for caliber because the material used in the bullets is lighter than the lead and jacket combination that we are so used to using. When loaded to standard Overall Length, these bullets take up more space in the cases. They are less compressible than the lead jacketed bullets because of the material used which means that the pressures created in the barrel will be higher. Performance or accuracy is usually found when the Barnes bullets are seated off the lands by and much as 0.050" and sometimes more. This reduces the powder space available even more. Throat angles, leade and barrel condition all add to the potential problems. The Lot # of a particular run of powder can be a big variable also.
I use the same bullets you're asking about but I have other variables that enter into my development so I can't just spit out my data and expect it to be correct for your rifle. The Norma website only lists their proprietary bullets in their reloading section no matter which powder is selected. Barnes doesn't list reloading data anymore.
Personally, I'd get on the phone to Barnes first and ask one of their technicians to help you with their data. You're using their product, they should know what the good starting points are for most cartridges. Then, to cover all bases, call Norma and get their data for the MRP/Barnes combination. Use a calling card, it's a cheap way to get information from overseas.
There are also websites with reloading information for virtually any combination but exercise real care with this data, I seen some that is outrageously wrong. Start low and work up slowly watching for signs of pressure. Use a chronograph.
I might look at starting somewhere around 73.0 gr. of MRP and work up slowly using a chronograph. Look at the cases carefully.
Sorry this is long but this gets asked occasionally and I wanted to cover the points of consideration besides trying to get you going.
Good Luck!
I am sorry it is a 300 Weatherby mag. It is also a Weatherby factory chamber
I did contact Barnes they have no data for the xlc with mrp but in their manual they do list it with the X bullet.
I think I will get 20 cases out and start at 73 as you suggested and load 20 cases up at half grain increments until I see pressure signs
thanks
Chester
From above:
"The Norma website only lists their proprietary bullets in their reloading section no matter which powder is selected. Barnes doesn't list reloading data anymore."
Best.