I've read some discussion in gun magazines about some bullets requiring deep seating in cases and that this takes away powder space. Usually this is stated as a negative.


For larger cased cartridges reloading manuals show that most powders don't come close to using all of the case capacity. So for those cartridges does deep seating of long bullets make any difference? What good is the case capacity if you can't put powder in it?

Just trying to understand things a bit better. Thanks for any help.

David

While reduced case capacity is one part of the issue with "deep seating," most people are concerned with getting the bullet close to the lands for optimal accuracy--sometimes resulting in the opposite question, "how little bullet needs to be in the case?" But this too is not a guarantee as some guns/bullets shoot better seated further off the lands.

R

It's actually not a negative at all if you are using one of the loads that leaves a lot of empty space in the case. However, if you want to use one of the loads with slower powders that fills up the case under the bullet, then it could get in the way of using that load. Most of my rifles seem to like slow bulky powder that fills up the case.

IMHO , this is something gunwriters like to fantasize about being relevant. Comparison of different cartridges/bullets from the perspective of looking at them " on paper ".

Actual results are that deep seating will raise pressure somewhat due to reduced case volume. Yeah, even though the space is not filled with powder it still matters pressure wise.

How much it matters to the actual bullet choice and maximum velocity attainable with a given pressure is less important than the performance of the bullet. ( A fancy way of saying " use what works, and don't sweat the small stuff ".)

I would gladly trade a little velocity for the correct bullet.

Travis F.

If you wanted to use the heaviest bullet in a particular bore diameter in your rifle, you would elect to have the bullet seated to be level with the base of the neck, so that the bullet has the best chance of being correctly aligned, and the full usuable case capacity is utilised providing a powder with the correct burning rate is selected.

However, usually rifles are throated so that the base of the bullet in the middle of the bullet weight range for that calibre is at or near to the base of the case neck,then obviously the heavier and longer bullets will then project below the case neck.

I have found that acceptable accuracy is still usually obtainable in these situations and as an example I recently accuracy tested and chronographed the Nosler 115 grain BT in a my 25/06 AI, and consistently obtained sub 0.5 moa groups from a slightly compressed load (63.0 grains) of Hodgdon 1000 and a velocity of 3,255 fps. In this instance this bullet is projecting about .080 inches below the base of the neck, as I had my gunsmith throat the rifle so that the base of the Nosler 100 grain BT bullet would be level with the base of the neck.

Currently there is very large number of powders commercially available covering a wide variety of burning rates, so even with cases with a capacity of up to 100 grains (and maybe larger) you should be able to select a powder that will give you a minimum of air space in the case.

To achieve the goal of 100% loading density, I measure the amount of powder it takes to fill the case to the base of the neck with the three basic powder types, and then look at one or more of the burning rate lists to see which powders are likely to be most suitable. To give you an example, a fireformed resized case in the newer of my two 25/06 AI takes:
71.1 grains of water to fill to the top of the neck
61.5 grains of long cut extruded powder (IMR 4831, 7828)to fill to base of the neck.
63.5 grains of short cut extruded powder (H1000, Re 22 etc) to fill to the base of the neck.
66.0 grain of ball powder (H870, Ramshot Magnum, etc) to fill to the base of the neck.

Hope the above information helps. Brian.