Hi Guys and Gals,
I was just looking around the web and found a a GREAT READ on the Border Barrel site describing a test they setup and the results.
It's helped me understand why a given load with high ES can still hold good vert.
You may already have seen it or already know the theory, but I found it very informative and enjoyed the read.
Thought it was worth posting.
http://www.border-barrels.com/articles/ ... barrel.htm
Great Info On Barrel Vibration
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johnk
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Good stuff, ain't it.
Bear in mind though that compensation & the ladder tests that we do that detect it are likely to be valid over a relatively small span of distances, which taken to a logical conclusion, would require us to tailor loads to s number of distance spreads.
The ultimately more desirable situation is to have a similar grouping outcome achieved from a load with a tight velocity spread. That load might be expected to perform acceptably over a greater range of distances.
Bear in mind though that compensation & the ladder tests that we do that detect it are likely to be valid over a relatively small span of distances, which taken to a logical conclusion, would require us to tailor loads to s number of distance spreads.
The ultimately more desirable situation is to have a similar grouping outcome achieved from a load with a tight velocity spread. That load might be expected to perform acceptably over a greater range of distances.
Yes it is a great read.
Bear in mind that at 1000 yards you would need to see around a minute of compensation exhibited over a 40-50 fps velocity spread. Whilst technically it might be feasible (much greater vibration speeds need to be generated) getting outside this would probably mean a reverse of similar magnitude and groups opening up horrendously.
In reality - you can get faster barrel vibrations by shortening and stiffening the barrel (e.g. barrel block) but this also has the secondary effect of reducing the overall magnitude of the vibrations such that you might have positive compensation but only over a very small window (say 20 fps and half a minute depending on lots of variables). Get out of this window and you have negative compensation!!
Chasing a "magic" spot rather than great velocity spread can show rewards but it will also require constant tuning and a reasonable velocity spread anyway.
At 300-700 yards - compensation seems to work very well.
Bear in mind that at 1000 yards you would need to see around a minute of compensation exhibited over a 40-50 fps velocity spread. Whilst technically it might be feasible (much greater vibration speeds need to be generated) getting outside this would probably mean a reverse of similar magnitude and groups opening up horrendously.
In reality - you can get faster barrel vibrations by shortening and stiffening the barrel (e.g. barrel block) but this also has the secondary effect of reducing the overall magnitude of the vibrations such that you might have positive compensation but only over a very small window (say 20 fps and half a minute depending on lots of variables). Get out of this window and you have negative compensation!!
Chasing a "magic" spot rather than great velocity spread can show rewards but it will also require constant tuning and a reasonable velocity spread anyway.
At 300-700 yards - compensation seems to work very well.
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DenisA
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G'day John and Dave,
I completely agree that tight grouping and low ES are fundamental basics to a good load.
However, its has eluded me for a while as to why in some situations during powder charge testing, a group can be shot, with random shots of increased velocity by 10 - 20fps and still hold the group and good vertical, but if you increase the powder charge by .2ish grains to bring the mean group MV up to that speed, the point of impact will sometimes increase and the group will sometimes move to the right slightly with a right twist barrel.
I think that article answers my question. It also illustrates clearly how barrel tuners work.
It doesn't suggest to me why sometimes groups with very low ES of 2-3 fps can group poorly.
I completely agree that tight grouping and low ES are fundamental basics to a good load.
However, its has eluded me for a while as to why in some situations during powder charge testing, a group can be shot, with random shots of increased velocity by 10 - 20fps and still hold the group and good vertical, but if you increase the powder charge by .2ish grains to bring the mean group MV up to that speed, the point of impact will sometimes increase and the group will sometimes move to the right slightly with a right twist barrel.
I think that article answers my question. It also illustrates clearly how barrel tuners work.
It doesn't suggest to me why sometimes groups with very low ES of 2-3 fps can group poorly.
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