https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/ AllGunStuff Discussion Board en-US Fri, 08 May 2026 07:06:57 +0000 wpForo 60 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4969 Tue, 30 Jul 2024 03:34:58 +0000 Reloading Methodology Tripodmvr https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4969 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4968 Tue, 30 Jul 2024 02:46:06 +0000
No.

Chris Long specifically developed the OBT theory as it relates to the annular wave cased by the powder explosion. The aim is to get the velocity SD down to a minimum by predicting when the annular wave is clear of the muzzle.

This is distinctly different from the Optimal Charge Weight theory that deals with the harmonic length of the barrel and how it whips around its axis.


I completely agree with you. The swing analogy was more for illustrative purposes and understanding. It is much easier for us mortals to imagine a swing with a stationary phase, than a metal bar with a wave like pulse travelling through it.]]> Reloading Methodology Againstthegrains https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4968 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4962 Mon, 29 Jul 2024 10:13:00 +0000
Thanks Againstthegrains, that's helpful. I got the wave form thing but hadn't clocked to the 'momentarily stationary at peak and trough' bit.

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Ya, i only caught on to that recently as well, like a piston in a motor - makes sense.]]> Reloading Methodology Treeman https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4962 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4961 Mon, 29 Jul 2024 08:59:22 +0000 Reloading Methodology oafpatroll https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4961 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4960 Mon, 29 Jul 2024 08:33:56 +0000
Chris Long specifically developed the OBT theory as it relates to the annular wave cased by the powder explosion. The aim is to get the velocity SD down to a minimum by predicting when the annular wave is clear of the muzzle.

This is distinctly different from the Optimal Charge Weight theory that deals with the harmonic length of the barrel and how it whips around its axis.]]> Reloading Methodology janfred https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4960 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4958 Mon, 29 Jul 2024 04:45:22 +0000
Imagine you are trying to shoot a target on a park swing that is moving.
If you aim for the target at the top of the upward swing when the object is momentarily stationary, and shoot when it reaches the top, then you have a much better chance of hitting than when the target is at the bottom of the arc of the swing when it is moving very fast.

If you get mathematical, and plot the speed of the swing on a graph as it goes back and forth, it will basically look like a sine wave. In other words, it slows as it reaches the top of the swing cycle and speeds up in between.

Now, when you shoot a bullet, the clever people (not me) figured out that it creates a wave through the barrel, and the tip of the barrel moves in a wave pattern, in other words, just like a swing, so if you release a bullet when the swing is up/ momentarily stationary, the bullet is released from the same point each time and the grouping will be good. If the bullet is released when the barrel is moving rapidly between stationary phases, the chances of the bullet being release from the same point each time is low, and hence the bullets are scattered around, and the grouping is poor.

Now, if you make the ropes of a swing longer, the swing will spend more time being almost still at the top of each passing, and take longer to get to the top of each side. It will also move at a higher velocity at the bottom/fast part of the swing cycle. In other words, changing the barrel length, is like changing the length of the ropes of a swing, and must be done for the OBT to work.

Now if you put it all together, it was a challenge for the developers of the theory to explain where the barrel will be moving fast and when it will be stationary, so they describe it (with whole lot of calculations I don't have a clue about) in terms of the time the bullet spends in the barrel before it is released, knowing that these times will correlate to points along the wave where the barrel is moving fast or is stationary. They called these "stationary" times where the barrel is hardly moving when the bullet is released, accuracy nodes, or Optimal Barrel Time (OBT). These barrel times equate to muzzle velocity or bullet speed. On a normal hunting rifle, the nodes are about 200ft/s apart.

So, if you have Gordon's Reloading Tool or Quick Load, and you can find the node # that fits within the pressure limits for that chambering that gives you a good fill % and powder burn rate with a specific bullet. Once you are there, load up a few tests either side of the predicted velocity. Go to the range, and see which test gives you that measured velocity (in the real world) and there you have it. The bullet should be releasing at the velocity where the barrel is predicted to be almost stationary, and therefor produce the best groups.

The other way of doing it, is the old fashioned way, where you shoot a ladder within the min and max velocities of the reloading guide, find your most accurate load, feed it into Quick Load, and suprise suprise, most of the time, your best grouping occurs at a velocity that equates with an OBT node.]]> Reloading Methodology Againstthegrains https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/3/#post-4958 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/2/#post-4882 Sun, 21 Jul 2024 06:46:19 +0000
I have gradually become a believer in the OCW method. I find the predictions with GRT to be way off with some powders, and certainly not good enough to be used as a predictor of pressure or velocity on its own. But what GRT is good at, is when you fill in the barrel length, and you get the velocity for each node. That's where the fun begins. The caveat, is that without a chrony to check, GRT is useless. I am finding that from the rifles I have loaded for, my best groupings occur when the velocity corresponds to a node for that barrel length.

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Would you in your own words try explain the OCW method, there is something about it that I just do not click with - I just do not understand it.]]> Reloading Methodology Treeman https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/2/#post-4882 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/2/#post-4865 Thu, 18 Jul 2024 11:32:56 +0000 Reloading Methodology Againstthegrains https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/2/#post-4865 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/2/#post-4819 Sun, 14 Jul 2024 09:12:03 +0000
The only Somchem propellant in one of our LGS was S265. No primers to be found. Somchem used to be half the price of imported propellants. I believe S365 was about R100 cheaper lately.

I believe the price ( unaffordability ) and unavailability of components is a bigger danger to the continued use of firearms in SA than any ham-fisted government action.]]> Reloading Methodology Newton https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/2/#post-4819 https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/2/#post-4817 Sun, 14 Jul 2024 08:04:34 +0000 Reloading Methodology Tripodmvr https://systemz.online/reloading-methodology/ocw-method-second-rifle-test/paged/2/#post-4817