opinions I need them velocity vs seating depth

mulemania

mulemania

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I loaded my 300 ultra mag and headed to the range yesterday
210g bergers .030 off lands retumbo poweder
89g 2950fps .5moa
90g 3000fps .5moa
91g 3050fps .65moa
92g 3100fps .95moa
93g 3130fps 1moa
94g 3150fps 1.25moa
95g 3220fps 1.5moa hot load no good

speed change was slow to my suprise.... I thought it would be more dramatic 28" barrel

my interest is.... i would really like this gun to shoot around 3100+
I have not changed seating depths yet and wanted to get some more input from others before wasting powder and bullets. I have read about shock wave theories, seating depths, nodes,...... everything under the sun. I was wondering In your opinions will changing the seating depths change the accuracy of these different powder charges???? for a 28" barrel and ultramag case 3000fps was not my goal.??? burger suggests loading at 010 030 050 080 i believe but i am not conviced that will fix the group from 1.25 down to .5 moa..... what do you all think
 
VLD Bergers almost always like being jammed. When i load develop, I automatically jam 10 thou and work from there. I know Berger said they have had reports that they work with lots of jump, but that has NEVER worked for me in the tens of thousands of their VLD bullets I've used in everthing from 224 - 338 caliber.

When you find an accuracy node, fine tune the seating depth to see if you can pull it tighter, but I always start jammed with VLD'sd
 
The only time they worked for me wasn't really jammed, enough to make marks on the bullet but still extractable. At 30 or 60 thou the groups opened up a lot for some reason. I still don't quite understand the theory as to why they do that.
 
My experience with Berger VLD has been some rifles like it jammed and some do much better well off the rifling. Yours appears to be the latter.

Nothing wrong with 0.5MOA. I would take that over extra velocity, any day and every day.
 
Every barrel/gun has a sweet spot between accuracy and velocity, I would say your is at 91 grains.

I've had rifles where the groups tightened up at all sorts of levels with a particular powder, the other thing that demonstrates this is the velocity spreads sometimes tighten up at a certain load and this usually gives better accuracy.

Pick your best combination, then mess with seating depth.
 
martinbns said:
Every barrel/gun has a sweet spot between accuracy and velocity, I would say your is at 91 grains.
Click to expand...

So in your opinion it's directly related to speed nodes and not the total combination? Could changing powders change the effects of the accuracy at different velocities? I had thought about trying us869 but heard its very tempature sensitive, 50bmg is too slow, I'm not filling my cases with 95g of retumbo, what powder is slightly slower and not so tempature sensitive
 
Barrel harmonics come into play. Each and every single gun is different. work with an empiracle seating depth and find the velocity that works best and THEN tune for seating depth. Fact of life that your accuracy node may not be at 3200. I have also found that Beger VLD bullets rarely shoot well above 3000 in any caliber. The closer you get to red line, the poorer a bullet performs. Maybe time to try another bullet. As Ganderite says, .5 MOA is good from a boomer like that. I'd take that any day from a heavy 30.
 
+1 here.

You data clearly suggest that you hit your node at 2950-3000fps. Your rifle has told you what velocity IT wants to shoot at.

The slow increase in FPS also suggest that you hit your max barrel length to burn rate ratio, and instead of gaining speed, you're pretty much just blowing extra gas out the end of the muzzle for nothing.

You'll get more barrel life out of a slower round anyway, that's splitting hairs tho.

I would recommend playing with factional chargers between 89-90g and/or sticking with one of those charges and playing with the OAL to see if you can tighten up further.
 
Here's what I've observed in the 300 RUM with the 208gr AMAX and US869 powder (in a 26" barrel):


3.650”
3.850”
101.0
2980
2990
102.0
3030
3020
103.0
3060
3050
104.0
3110
3100
105.0
3140
3110
106.0
3170
3140


With Retumbo, I saw something different:


91.0
2830
2870
92.0
2930
2950
93.0
2990
3000
94.0
3000
3080
95.0
3060
3080

By way of explanation, since there is less powder used and hence more unused powder space with the Retumbo loads (although US869 is more dense than Retumbo....), the seating depth (0AL) would have to be further reduced to observe the effect - speculation on my part.

We know that seating close to the lands (0.050" or closer), increases pressure (and MV) and seating deeper does the same, and in-between (most noticeable in large rifle cartridges) is a zone where the pressure is less. This has nothing to do with accuracy, only pressure.
 
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