Some .300 win mag load data

[user293]

Me and my buddy have been doing some load development, mostly for hunting. .300 mag has a 26" barrel (just had it rebarreled, and restocked) ive been using two bullets, the barnes 175 gr LRX .508 BC for my hunting round (which is kinda hard to find now) and the 180 gr nosler ballistic tip (mostly for practice). I have two powders for the .300. rl-22 and H-4831SC. I have found that h4831 is not very good for velocity but the accuracy is good. velocity for 73.5gr of 4831, Barnes LRX was 3066, 3058 and 3072 for a SD of 7.0 and extreme spread of 14.1. that's good in my book but the velocity sucked. 72.7gr of h4831 LRX yielded 3061, 3071, 3072,and 3058 with and SD of 6.9 and ES of 14.1 again. super good load, but velocity sucks. reloader 22 is a different story in my rifle. i loaded up some at 73 gr and 73.5 (73.5 is max from barnes) i shot the max load first because i didn't see much for pressure signs out of the 73 gr load. so heres the data: 3284, 3273 and 3286. SD of 7.1 and ES of 13.5 and the velocity kicks major ass. good accuracy too. the bolt gets a bit sticky before it opens up but it aint terrible. i never thought id get over 3150 with this bullet. i tried the 73 gr. rounds and they were a little over 3200 fps. yea move over 300 ultra mag. so im gonna back off the load to 73.2 gr or so and check some long range accuracy and play with OAL and off lands measurements. this chronograph however is an old Pact mk5 i think from like '93. its old but works and still prints your data. im getting a new chrony soon so should be able to cross reference. magpro worked very well in my buddies .264 win mag. he got like 3500 FPS with a 120 gr amax and still had room to play. rl-22 worked well for him too as well as IMR 4831. so that's the story. anyone with a .300 feel free to chime in. i still wanna play and get this bullet to work.

[Seismic Sam]

Very impressive SD's. How many shots for each string, and how many strings did you shoot at different powder weights, and what were the weights?

Also got lost on which bullet you're trying to make work.

Generally, I do ten strings of 5 each to work up a rifle load in two tenths or three tenths grain increments, and all the loads are individually weighed, as well as all the other stuff you have to do to get benchrest accuracy. Unfortunately, I shoot .338 Ultramag, and those are in a different league and powder category than 300 Win Mag, so I can't give you any relevant direct advice on that cartridge. After you get the data it helps to plot the average velocity and all the raw velocities on a chart in Excel, so you can see the shape of the Average curve and the scatter width of the raw data, which is the ES of the sting and lets you pick out the smallest SD almost immediately.

[user293]

usually 3 or 4 shots per powder weight. new string for each change in weight or powder. all those were with the 175 gr barnes LRX bullet.

[Seismic Sam]

Not to be too picky, but you need to standardize on a string length, and the conventional wisdom is that you need 5 shots for the SD to mean much. Worse than that, you can REALLY lead yourself astray by comparing SD's of 3 shots with SD's of 4 shots or 5 shots. I'm not up enough on the stat theory to give you hard comparisons, but an SD of 12 with 5 shots could very well be more consistent than an SD of 9 with 3 shots. Caveat emptor.

EDIT: Just occurred to me that with the Millenium chrono stats, the software produces a 95% confidence level of it's SD calculation, so if you do SD and 95% confidence level for a different number of shots, the fact that the SD is lower but ALSO that the confidence level has dropped may alert you to the fact that the SD value looks better than it really is. The only problem is that I'm not sure a confidence level for just three data points is mathematically valid or has any real meaning. Statistics are meant for substantial groups of data to show averages and other values, and I'm not sure that whole discipline can really be applied to just 3 data points.

[liferefugee]

It can be applied but with a very low confidence level. 5 should be a minimum, 10 is even better.

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[Seismic Sam]

It can be applied but with a very low confidence level. 5 should be a minimum, 10 is even better.

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Thank you!! I kind of figured that from the fact that if you didn't have 5 shots in a string, your Millenium chrono would refuse to calculate an SD for you. Plus there's this even-odd thing, where if you have an odd number of points, the SD has a chance to be centered near an actual data point, while with 4 points you could have two high and two low, and the SD would be centered on a blank area in the scatter chart.