"Best" powder for .223 Hornady bullets?

Toprudder said:

Being a fast burning powder, it won't generate as much gas as slower powders, which is why I liked it for my AR pistol. The min charge of 19.0gn of H4198, 55fmj bullets, operated the pistol just fine. I have used it for 55fmj loads in my mid-length 16" carbine. It has to be at the top of the charge range to reliably cycle and lock open, though. The max charge was listed as 21.0gn, and at 20.5 it operated reliably. Soft shooting load. I think it would be worth a try, just to see if you like it. I don't know how much difference there would be between IMR4198 and H4198, though.

Click to expand...

The burn rate doesn't affect the amount of gas generated, the charge weight does. More powder = more gas volume.

Burn rate DOES affect the SHAPE of the pressure curve, however. Being a relatively fast powder, the pressure at an AR's gas port may be lower than that produced by slower rifle powders.

Both of these factors drive another issue observed with H4198 in ARs: That low amount of gas generation and low pressure at the gas port make it unsuitable for guns with rifle-length gas systems. That max charge generates enough gas at a high enough pressure to cycle pistol and carbine length gas systems, but not the mid- and rifle-length versions.

More discussion here:

https://www.thehighroad.org/index.p...-rifle-length-gas-system.780506/#post-9911806

luzyfuerza said:

Both of these factors drive another issue observed with H4198 in ARs: That low amount of gas generation and low pressure at the gas port make it unsuitable for guns with rifle-length gas systems. That max charge generates enough gas at a high enough pressure to cycle pistol and carbine length gas systems, but not the mid- and rifle-length versions.

Click to expand...

Just one more reason that H4198 is the one powder I don't recommend for .223/5.56 cartridges. The others being lack of velocity, mediocre accuracy and very poor metering through my Uniflow powder measure. Based on my experience, yours may differ.

I have found that RL7 is another that will not cycle a rifle length gas system.

luzyfuerza said:

The burn rate doesn't affect the amount of gas generated, the charge weight does. More powder = more gas volume.

Click to expand...

Well, yes, but faster burning powders require smaller charges to stay under the max pressure. In the case of H4198 and 55fmj bullets, the max charge is 21.0 grains. I don’t know that 21.0 grains of something like H335 would be desirable or practical. When I look for lower velocity loads in pistol, I prefer using faster burning powders instead of downloading slow powders.

Burn rate DOES affect the SHAPE of the pressure curve, however. Being a relatively fast powder, the pressure at an AR's gas port may be lower than that produced by slower rifle powders.

Both of these factors drive another issue observed with H4198 in ARs: That low amount of gas generation and low pressure at the gas port make it unsuitable for guns with rifle-length gas systems. That max charge generates enough gas at a high enough pressure to cycle pistol and carbine length gas systems, but not the mid- and rifle-length versions.

Click to expand...

Max charge cycles my mid-length 16” carbine just fine, but I guess it may not cycle others. While some would not consider it a good powder, that depends entirely on the application. The low pressure at the gas port also means lower pressure at the muzzle, which relates to the lower flash and bang that I was looking for in my AR pistol.

FWIW, many, almost any of the middle-burn-rate powders work well in the .223 and cycle well in carbine-length gas systems. Varget, IMR 4895 and 4064, etc. I think Varget is a preferred powder as you get into the heavier .223 bullets, like 69 gr. and above.

I've had really good results with RL-15, and it's known to be one of the more temperature-stable powders. By good results, I mean 1" groups at 100 yds. with match bullets from a scoped 20" AR with an Olympic barrel. Plain old 55 gr. FMJ's more like 1.5-2.0".

I don't think the OP said what kind of accuracy he's expecting, or if he's using an optic, but I'd be curious to know.