case capacity

[luteai]

I've only been doing this 30 + years, but for the first time noticed a big discrepancy in case volume. My Hornady 30-06 cases hold a full 3.5 grains more 4350 than the Federal and Remington cases I normally use. Should I expect different velocities from the same powder charge? 57 grains of IMR4350 has no rattle at all in fed or rem, still has open space in the Hornady. 

[yorketransport]

I'd expect to see a pretty big difference between the different cases. You've essentially reduced your case capacity making a load that used to be say 93% case fill and now it's 100%. That will increase your pressures and your velocities all else being equal.

[luteai]

I may break out the chrony.  Load is listed in 3 manuals, but I'm curious as to velocity difference. 3.5 grains more capacity in the Hornady "06 cases. Never ran into anything that different in volume.

[yorketransport]

Sorry, my statement is backwards. The hornady case will have lower pressure with the same charge compared to the federalbpr Remington brass. In my head I was thinking the hornady case had the lower capacity.

[Yondering]

It's the same scenario as 308 commercial vs 7.62 military brass. Do some reading on that if you want more info on this topic. It's well known to reduce charges in mil brass (compared to the same load in commercial brass) for 308, to account for the reduced case capacity.

As a side note- some guys get mixed up and do this for 223, but it doesn't apply there; mil and commercial brass weights are very similar.

[JDHasty]

We have found Horandy 17 Hornet brass to vary quite a bit.  Hornady makes two weights of 17 hornet cases and we have found both weights in the same lot of loaded ammunition. 80% of one "lot" of 450 cases weigh 50.6 gr give or take a couple tenths, the remaining 20% weigh 56.4 gr. again give or take a couple of tenths. (A classic bimodal distribution).

Hornady advertises on their website: "Consistent Weight and Capacity Every single Hornady case, regardless of the lot in which it was produced, is virtually identical to other Hornady cases in the same caliber. For you, this means consistent pressures, velocity and accuracy — every time."

[Magnum_Willys]

If it was a 180 gr bullet with same 57 gr 4350 load quickload says:   

2851 fps @ 63104 psi for small case
2791 fps @ 56688 psi for case 3 gr larger.

[luteai]

thanks for the quick load data(165 grain bullet for me) I'll see how they do tomorrow. more interested in point of impact difference than velocity though they go hand in hand.

[luteai]

Did not get to use the chrony at the range.  the Federal brass printed 2 inches higher than the Hornady with the same load. no noticeable recoil increase or pressure signs.  Me thinks there's a velocity difference between the two cases!