Handloading the AR-15 .223 with 1-in-9 twist Pt. 2
Date: Feb 29 2008
In the last issue of LoadData.com, we covered basic loading tips for the AR-15/.223 Remington rifle featuring a one-in-12-inch twist barrel. For those who did not catch that piece, let’s briefly touch on some important handloading points, points that also apply to handloading an AR-15 fitted with a one-in-9-inch twist barrel. Cases should be sized (using either a small-base or full-length sizing die) to allow cases/cartridges to chamber easily. Overall cartridge length should generally be limited to 2.260 inches to allow cartridges to function correctly in the magazine. (If they exceed this length, they tend to hang up in the magazine or won’t fit at all and jeopardize the reliability of the rifle.) A cartridge’s “trip” from the magazine to the chamber is rather rough, so bullets should be crimped in place, even those without a cannelure. Avoid mixing cases, and never use military cases with data developed for commercial cases, as dangerous pressures can result.
AR-15 rifles with a one-in-9-inch twist will stabilize bullets weighing from 55 to 75 grains. This allows them to be useful for varmint hunting and competitive on 600-yard “match” targets. In this respect, this twist is clearly the most versatile and best all-around twist rate offered in an AR-15 and explains why it is the most common in use today.
In the accompanying table, data for 55- to 60-grain bullets has been omitted, as all loads presented for rifles featuring a one-in-12-inch twist barrel in the last issue are also suitable for rifles with the one-in-9-inch twist. One item to be aware of is that lightly constructed frangible 55-grain “varmint” bullets can disintegrate in midair due to the high revolutions per minute (rpm) rate. Additionally, scientific tests have proven that these frangible bullets can actually be stressed in the throat/rifling wherein the jacket and core begin to separate due to high pressures (and not velocity) while still in the barrel, which can cause the bullet to come apart shortly after leaving the muzzle. If this is the case, using loads that are 5 to 10 percent below maximum might help prevent bullet break-up and allow the AR-15 to be used successfully with varmint bullets.
Avoid substituting one bullet for another of the same weight, but from a different manufacturer, especially once a load has been developed that is near maximum. For instance, it is common to develop a load with a given bullet, then switch to a bullet of the same weight from a different manufacturer. Differences in the gilded jacket, bullet profile, bearing surface and other factors can result in a significant change in pressure. This potential problem seems especially pronounced when loading the .223 Remington with 65-grain and heavier bullets. The list of suitable powders for handloading the .223 Remington is lengthy. Ball powders have become especially popular, as most meter uniformly and allow the powder to be thrown from a measure with minimal charge variances. And their performance in terms of accuracy and velocity is impressive, with many match competitors turning in impressive scores. Examples used in my data include Hodgdon H-335, H- 380 and BL-C(2), Winchester 748 and Accurate Arms AAC-2230.