Trying To Understand Powder Data

[KAC1911]

When reading load information from a particular powder company they are giving you recipies for their powder. For sake of this discussion, for .223 with a 24" barrel w/1:7 twist they are giving various bullet weights and powder types.

Now I have a 16" w 1:8 twist. From the data the powder company is supplying how do I determine what would work in my rifle? Do I start with a bullet weight I want to use or a type of powder I want to work with?

I realize as with all you begin with the starting recomendation of powder too.

 

[Shoney]

how do I determine what would work in my rifle? Do I start with a bullet weight I want to use or a type of powder I want to work with?

The first thing is to determine which bullet is best for the twist. Well known barrel maker Lilja says 80gr is ideal, so weight from 69 to 90 may also work well.

Then you pick a powder (or whatever is availability).

 

[KAC1911]

So I guess you start shooting different weight factory loaded bullets first to determine what works better in your barrel, then you stick with that weight bullet and start working loads for it?

 

[SteveW-II]

Right, but keep in mind that your 16" barrel is not going to produce the same muzzle velocity as the 24" barrel the powder vendor is using.

If you start to use a chronograph to 'chase the velocity' past the maximum load that the vendor recommends you will get into a over pressure situation very quickly. So.. The the max load data isn't to be exceeded even if you don't get close to the velocity listed in the book. For example my 16" barreled AR only gets 2800 fps from a load that exceeds 3000 fps from a 20" barrel.

With respect to the barrel twist, what stabilizes the bullet is the number of revolutions per second. Don't assume that the twist that stabilizes a bullet from a 24" barrel will stabilize the same bullet with the same load from a 16" barrel. Revolutions per second from a given twist will depend on muzzle velocity. The 16" barrel may not produce enough muzzle velocity to impart enough spin to stabilize heavy bullets.

 

[NCsmitty]

you stick with that weight bullet and start working loads for it

Roughly, that's how it works. It's not difficult to study the powders that the manuals recommend for the round that you're using, and compare the burn rates, and their relationship to the bullets that may work best in your firearm. If you take the time to understand, it will pay off in safe, accurate reloads.



NCsmitty