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COAL and Jump


Newbie1962

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Loading Barnes TTSX 180 gn for 30-.06. According to The Barnes Manual, COAL for this combination should be 3.218. My rifle chamber measures 3.374 to the rifleling. The jump seems excessive if I use the recommended COAL. Based on my web trolling, it looks like the common jump recommendation for this bullet is roughly 0.05-0.08. Was thinking about loading it to 3.300 (the same COAL I use for several other other bullets). Any reason not to? Any advice?

Thanks

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Barnes bullets are usually the most accurate for me at there recommended oal. I have moved them out slightly and they were no where near as accurate. I have also shot the same loading in a 223 chamber and a 556 chamber the latter having a longer jump both were about equal shot the same day. I know that's a smaller bullet and i have not tried similar test with my 30-06. I also have not tried the 180's i have only used the 150's in my B.A.R.

The tsx and ttsx have what i believe they call the driving bands. If you load them longer you may land in between the bands. Barnes bullets are not really jump sensitive like a vld style bullet.

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  • 8 months later...

Bullet jump is a safety device for the gun manufacture, with that much free bore the pressures can be kept within a normal c u p

Pressure. A benchrest rifle is set up with little or no jump, but the powder charge is cut back several grains, it's best too load by the recommend spec. For safety reason's.

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While its always important to pay attention to seating depth, in most cases it matters little unless you are at the high end of pressure. Seathing bullets deep or into lands will raise pressures. With solid bullets you have to be careful as jaming them will get your pressures up quick as solids will generate pressure more than a traditional bullet.

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