A question about accurate vs max loads.


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longrifleman
December 30, 2005, 03:22 PM
I was thinking about the different loads I've worked up and so far the most accurate has never been the maximum load for any given bullet and powder combination. I haven't done that many for that many different calibers, so I was wondering if there was a correlation with heavier calibers liking heavier loads, or any patterns like that.

Sometimes the difference in accuracy has been minimal, so more velocity might be useful, but no big deal. Does anyone else have any different experience?

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USSR
December 30, 2005, 03:50 PM
longrifleman,

Tribal knowledge says that most times there are a couple accuracy "nodes" at different velocities with cartridges. However, as you noticed, it is rarely at what is considered to be a maximum load.

Don

Vern Humphrey
December 30, 2005, 03:59 PM
Theoretically, a rifle is most accurate when the bullet exits at a vibration node. If your bullet is exiting near a node, the vibratory motion of the barrel is very small. If it exits between nodes, the motion will be large.

That explains why increasing or decreasing velocity seems to improve accuracy when working up loads. Some rifles shoot well at max velocity, because that's where the node is. Others require you to back off a bit.

georgeduz
December 30, 2005, 04:08 PM
thats true with handguns,the slower is better,but in rifle faster is better,i think 3000fps and over works the best.(vibration node)never heard that one before.vern where did u get that info from i like to read it.

Vern Humphrey
December 30, 2005, 04:16 PM
thats true with handguns,the slower is better,but in rifle faster is better,i think 3000fps and over works the best.(vibration node)never heard that one before.vern where did u get that info from i like to read it.

If you have access to back issues of The American Rifleman, they did a piece some years back on a study of vibration in rifle barrels and the effect on accuracy. The Browning Boss is based on that work -- it allows you to tune the barrel to the load, instead of tuning the load to the barrel.

Dave R
December 30, 2005, 04:22 PM
I handload for 4 rifles, and have found only one case where an accurate load was near a max load. Its a .308. Other than that, the accurate loads have been less than max. Which is fine with me. When you make a good hit, the extra 100-200fps ain't gonna matter.

longrifleman
December 30, 2005, 04:42 PM
[QUOTE][Theoretically, a rifle is most accurate when the bullet exits at a vibration node/QUOTE]

Theoretically, I understand the node concept. I wondered if anyone had noticed a pattern with different classes of cartdriges preferring max vs milder loads. I'd also be interested if anyone has noticed a preference for barrell lengths for different rounds also.

bogie
December 30, 2005, 09:04 PM
Yes.

Clark
December 31, 2005, 02:49 AM
Some rifles like it hot, some like it cold, some like it in between, some don't care, and some won't shoot anything right.

I own examples of all these rifles.

Grumulkin
December 31, 2005, 06:52 AM
Part of the answer lies in how you define maximum loads. A particular firearm may exhibit signs of excess pressure sooner than another of the same caliber. If you compare what are called maximum loads for the same bullet weights, powder weights, etc. for a particular caliber you will also find significant differences when you compare the data from different reloading manuals.

What I have found in general is that if you make progressive handloads starting from the lower end of powder weights the groups initially will be large and a point will come at which they get smaller and then larger again. I have one .308 Win. that likes 41 grains of IMR 4064 with 168 grain bullets and another that does better with 43 grains of IMR 4064 both of which are less than "maximum loads" in reloading manuals. My 357 Herrett does best near maximum published loads and with CCI 250 Magnum primers vs Federal 210M match primers.

The "node" theorey makes some sense. If true, a shorter thicker barrel (i.e., stiffer barrel) should be less subject to this phenomenen. I suspect other factors include chamber pressure (which will vary depending on how tight a particular chamber), barrel twist rate (which will also affect chamber pressure), etc. which will affect how fast the bullet exits the barrel and how consistent the burn rate is in the chamber.

win71
December 31, 2005, 07:38 PM
I don't know about these scientific explanations I'm reading here but they do sound good. What I have experienced is similiar to Longrifleman. In the small calibers I load for, .22 hornet, 222, 22-250, and 243 all shot better at less than listed maximums in any of several reloading manuals. Except for the hornet they are varmint weight barrels. Recently I got into the 204 ruger game and this is the odd man out. I'm over max on three different powders and the faster the 30,32,and 35 gr. bullet goes the better it shoots. I'm not even close to the speed of the factory claimed velocities. All of the best loads were grouped shooting through a chronograph. All of the larger calibers in hunting rifles shot better at less than max listed charges. One in particular, a pre 64 mod. 70 .270 shot good at quite a bit less than max and in fact wasn't as fast as I wanted to hunt with. A gradual increase in 1/2 gr. increments slowly increased the group size until I got near the speed I wanted with a satisfactory group size for hunting, about 1.50 moa. For clarity when I use "max load" I am refering to what is listed in several reloading manuals and not a max load for any particular rifle. Unless I missunderstood Longrifleman that was what he was referring to.

Kamicosmos
December 31, 2005, 07:53 PM
Also, the rifle's barrel twist has a lot to do with it, especially in smaller fast cartridges. Look at .223 for all kinds of reloading fun depending on twist rate. some guns are setup for light superfast bullets, others are set up for heavier, slower bullets.


Anyone what to explain the Vibration stuff in relation to twist rate? I would imagine that the two are pretty intertwined with each other. (pun intended! ;) )

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