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Old 02-26-2012, 12:24 PM   #1
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Default Load Data Discrepancies?

I’m looking at the load data for 175gr 308win and I’m seeing some pretty big discrepancies. The min. load from the powder manufacturer is almost the same as the max load from the bullet manufacturer. The two sets of data are for the same components including the same brand of bullet. I’m guessing the difference is the rifle used to develop the data? The bullet manufacturer used a 26” barrel with a 1:10 rate of twist, which isn’t very representative of most .308’s. I do not know what was used by the powder manufacturer.

Is it common to see these kinds of discrepancies for load data?



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Old 02-26-2012, 12:45 PM   #2
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If you look in several different load manuals,you will see a wide range of differences in the same load data.

I will load up until I see high pressure signs,and then back it off some if that's where the best performance for a particular bullet is.
Most of my guns shoot better with middle of the load data range,but I have a few that like them pretty hot.



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Old 02-26-2012, 12:49 PM   #3
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Yes its common. Thats why you need to consider the barrel length used. I use several load manuals and try to pick recipes with test data that closely match the barrel im using.

General rule is reduce charge weight from max by 10% and work up slowly.

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Old 02-26-2012, 04:51 PM   #4
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I reference several reloading manuals and see a big difference between them for the same cartridges. I use a lot of Hornady bullets and have noticed that their load data is pretty conservative compared to the others. I follow their recommendations when using their bullets and have had good luck. I think it is really important to make note of the firearm and components used to do the testing and compile the load data. There are a lot of variables involved that can affect performance.

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Old 02-26-2012, 11:09 PM   #5
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Thanks

Just out of curiosity do any of you have a particular method for working your way up such as an extra % at a time or is it just something based on experience?

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Old 02-27-2012, 01:28 AM   #6
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Quote:
Originally Posted by TLuker View Post
Thanks

Just out of curiosity do any of you have a particular method for working your way up such as an extra % at a time or is it just something based on experience?
Now I work my way up based on my experience. I have been reloading for about 30 years. I have tried to make note of what works and what does not. As a general rule I work my way up at half-grain increments for rifle cartridges and will even go to increments of one-tenth of a grain for handgun loads. This is a rather simple explanation, as the powder I am using will make a difference. I shoot the different loads from a rest and check how they group. I also check the velocity with my chronograph. I look for signs of excessive pressure, such as primer cratering and brass deformities. I know some loaders will keep going up and up but I stay within a specified range, usually the load data for the specific bullet I am using. I hope this helps. I can tell you that I have learned a lot about what not to do from loaders who were not very careful and made mistakes.
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Old 02-27-2012, 02:20 PM   #7
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"I’m guessing the difference is the rifle used to develop the data?"

Correct. It's much more than barrel length, which has no effect on max charges at all. YOUR rifle is still different so we're always told to 'satrat low and work up slowly....," etc.

Choose any method of charge increase you're comfortable with but few of us bother with percentages. I move up in .2 gr steps with small cases, .3 gr in medium and .5 gr with the really big boys simply because I've found that to be plenty small enough for safety and for finding a good load too.

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Old 02-27-2012, 04:07 PM   #8
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Barrel length and its effect on velocity is discussed all the time. I was testing my .44 mag loads in my Super Blackhawk with a 7.5" barrel. I was using the Hornady 240-grain XTP with three different powders, H110, 296 and Lil' Gun. At the same time I was having a friend try the same loads in his Henry rifle with a 20" barrel. We were using a chronograph to measure the velocity. The velocity of the bullets coming out of the rifle were about 200 fps faster than my pistol. We got some very consistent velocity with both firearms with all three loads. The grouping was really good with both guns also. If it means anything the bullets coming out of my Super Blackhawk averaged in the 1350 fps range.



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