Thread: Inaccurate Cartridges

Much is made recently of the inherent accuracy of having a short fat powder column. wsm saum br etc
Yet many get great results out of 30-06/6.5 etc

I have no experience to quantify the differences but am interested where this thread will head.

Originally Posted by veitnamcam

Much is made recently of the inherent accuracy of having a short fat powder column. wsm saum br etc
Yet many get great results out of 30-06/6.5 etc

I have no experience to quantify the differences but am interested where this thread will head.

VC, I'm pretty sure this short fat column primarily promotes efficiency with the powder burn and this leads to being able to finely tuning the accuracy with smaller increments of powder. Some of our bench resters may be able to confirm this

Originally Posted by veitnamcam

Much is made recently of the inherent accuracy of having a short fat powder column. wsm saum br etc
Yet many get great results out of 30-06/6.5 etc

I have no experience to quantify the differences but am interested where this thread will head.

@veitnamcam,

The 30/06, despite of any long-powder-column disadvantage if such exists, will have one advantage from its long case length: A LONGER cartridge will more readily line up with the bore axis, which in turn helps its bullet engage with the rifling on-axis.

A bullet which is perfectly balanced on the rifling axis is less like a corkscrewing aerobat before its spin eventually stabilises it at some point of its corkscrew. This is why some large groups often describe circles (with the centre less densely holed, rather than a uniform peppering of holes covering the entire area of a circle).

Originally Posted by Cordite

@veitnamcam,

The 30/06, despite of any long-powder-column disadvantage if such exists, will have one advantage from its long case length: A LONGER cartridge will more readily line up with the bore axis, which in turn helps its bullet engage with the rifling on-axis.

A bullet which is perfectly balanced on the rifling axis is less like a corkscrewing aerobat before its spin eventually stabilises it at some point of its corkscrew. This is why some large groups often describe circles (with the centre less densely holed, rather than a uniform peppering of holes covering the entire area of a circle).

Yes but would be mitigated by close chamber dimensions.

I was hoping someone may have burnt a couple of barrels in a target rig with a long case and gone to a short and fat case in a apples with apples comparison.

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Originally Posted by veitnamcam

Yes but would be mitigated by close chamber dimensions.

I was hoping someone may have burnt a couple of barrels in a target rig with a long case and gone to a short and fat case in a apples with apples comparison.

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@vietnamcam

Apples for apples, I was thinking of long vs short cartridges, both in military loose chambers. With the exact same tolerances employed, the longer cartridge will of course be more likely to sit on-axis. But how big that effect is for accuracy... who knows.

To help cartridges sit concentric with the rifling bore, some advocate putting a thin O-ring round the base of the cartridge, a couple mm ahead of the rim on rimmed cartridges or extractor groove on non-rimmed cartridges, to help keep the case body centered in the chamber. Helps ensure the bullet engages concentric with the bore. Of course this is also nifty if you reuse cases and that first shot fireforms the brass for your chamber, and only neck sizing from then on. To be completely obsessive, you'd also mark 12 o'clock on the rear face of the cartridge, in case the chamber is assymmetric, and from then always chamber it 12 o'clock up.