Thread: Short barrel 223 build ?

Originally Posted by 7mmsaum

...
Partial neck size only to increase case capacity...

?? By 0.1%?

Only gain to be had here is to go for the lightest brass available, and that going to be pretty insignificant at best. Sizing treatment isn't worth chasing IMHO.

Originally Posted by 6x47

?? By 0.1%?

Only gain to be had here is to go for the lightest brass available, and that going to be pretty insignificant at best. Sizing treatment isn't worth chasing IMHO.

In a .223, full length resized lapua match brass and 60g nbt mag fit held 26g of 2206h

3206fps


Neck sized only and same projectile and seating depth held 27.1g of 2206h

3450fps

If you are shortening your barrel and want some lost velocity back there are a few ways to increase powder capacity, neck sizing is one way, another way is to increase throat lead to the rifling which allows you to make ammo with a longer overall length, again opening up case capacity for more powder

The lightest .223 brass with the largest internal capacity cant normally handle higher pressure, lapua brass can.

Broadly speaking Pressure = velocity in a short tube

Try not to use moly or HBN coated projectiles as pressure is usually reduced, dropping velocity.


The effect in short barrelled 08cases and saums is even more dramatic

Running lapua brass with its .588 bolt face and ..585 base dia shortened to saum length has an even bigger capacity advantage when neck sized only.

When using a .223, and a short tube at that, any extra velocity is welcome.




When designing a short barrelled .223 consider the effect your slower projectiles and reduced energy are going to have on your maximum range and the animals you shoot, and rather than running ammo at high pressure levels put some thought into a short tube on a .22PPC or .22XC or 22-250 that will give far better velocity in a short tube, and do it with less brass/ammo prep.

Originally Posted by 7mmsaum

In a .223, full length resized lapua match brass and 60g nbt mag fit held 26g of 2206h

3206fps


Neck sized only and same projectile and seating depth held 27.1g of 2206h

3450fps

If you are shortening your barrel and want some lost velocity back there are a few ways to increase powder capacity, neck sizing is one way, another way is to increase throat lead to the rifling which allows you to make ammo with a longer overall length, again opening up case capacity for more powder

..

The latter is certainly an option to buy more case capacity- more freebore (longer leade) will do that but often at the cost of your magazine being too short to get suitable jump for max accuracy.

I find it very hard to believe that a 1.1gr increase in case capacity will produce anything remotely approaching 250fps vel gain. If you look right down the column of 60gr proj loads in the Hornady handbook, that final 100fps up to "max" needs between 0.7 - 1.1grs to achieve this. So this means you're talking at least 2grs and probably 3grs with other powders to get an extra 250fps.

The only way to get ~250fps will involve changing some other major variables such as powder type.